[syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel..
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d39e9f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=37c006d80708398d
dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16215ca9980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/80466d230dfb/disk-94106455.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ba253eabab42/vmlinux-94106455.xz
kernel image: https://storage.googleapis.com/syzbot-assets/569982fb6c88/bzImage-94106455.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com

IPVS: Unknown mcast interface: macvlan0
netlink: 8 bytes leftover after parsing attributes in process `syz-executor297'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor297'.
======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-01458-g9410645520e9 #0 Not tainted
------------------------------------------------------
syz-executor297/5243 is trying to acquire lock:
ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674

but task is already holding lock:
ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (rtnl_mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       start_sync_thread+0xdc/0x2dc0 net/netfilter/ipvs/ip_vs_sync.c:1761
       do_ip_vs_set_ctl+0x442/0x13d0 net/netfilter/ipvs/ip_vs_ctl.c:2732
       nf_setsockopt+0x295/0x2c0 net/netfilter/nf_sockopt.c:101
       smc_setsockopt+0x275/0xe50 net/smc/af_smc.c:3064
       do_sock_setsockopt+0x3af/0x720 net/socket.c:2330
       __sys_setsockopt+0x1ae/0x250 net/socket.c:2353
       __do_sys_setsockopt net/socket.c:2362 [inline]
       __se_sys_setsockopt net/socket.c:2359 [inline]
       __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2359
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&smc->clcsock_release_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       smc_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902
       smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2771
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg+0x221/0x270 net/socket.c:745
       ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
       ___sys_sendmsg net/socket.c:2657 [inline]
       __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (sk_lock-AF_INET){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
       __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
       lock_sock_nested+0x48/0x100 net/core/sock.c:3611
       lock_sock include/net/sock.h:1609 [inline]
       gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674
       gtp_encap_enable drivers/net/gtp.c:1707 [inline]
       gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511
       rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
       __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
       rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743
       rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646
       netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
       netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
       netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
       netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
       sock_sendmsg_nosec net/socket.c:730 [inline]
       __sock_sendmsg+0x221/0x270 net/socket.c:745
       ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
       ___sys_sendmsg net/socket.c:2657 [inline]
       __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_INET --> &smc->clcsock_release_lock --> rtnl_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rtnl_mutex);
                               lock(&smc->clcsock_release_lock);
                               lock(rtnl_mutex);
  lock(sk_lock-AF_INET);

 *** DEADLOCK ***

1 lock held by syz-executor297/5243:
 #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643

stack backtrace:
CPU: 0 UID: 0 PID: 5243 Comm: syz-executor297 Not tainted 6.11.0-syzkaller-01458-g9410645520e9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2186
 check_prev_add kernel/locking/lockdep.c:3133 [inline]
 check_prevs_add kernel/locking/lockdep.c:3252 [inline]
 validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
 lock_sock_nested+0x48/0x100 net/core/sock.c:3611
 lock_sock include/net/sock.h:1609 [inline]
 gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674
 gtp_encap_enable drivers/net/gtp.c:1707 [inline]
 gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511
 rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
 rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743
 rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
 netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
 netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
 ___sys_sendmsg net/socket.c:2657 [inline]
 __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fed198844a9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RS


---
This report is generated by a bot. It may contain errors.
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syzbot will keep track of this issue. See:
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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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#syz undup

Re: [syzbot] test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: test
Author: danielyangkang@gmail.com

#syz test

Re: [syzbot] patch test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: patch test
Author: danielyangkang@gmail.com

#syz test

Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[Hillf Danton]

On Mon, 23 Sep 2024 08:46:24 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel..
> git tree:       net-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000

#syz test

--- x/net/smc/af_smc.c
+++ y/net/smc/af_smc.c
@@ -3053,9 +3053,7 @@ int smc_setsockopt(struct socket *sock,
 	/* generic setsockopts reaching us here always apply to the
 	 * CLC socket
 	 */
-	mutex_lock(&smc->clcsock_release_lock);
 	if (!smc->clcsock) {
-		mutex_unlock(&smc->clcsock_release_lock);
 		return -EBADF;
 	}
 	if (unlikely(!smc->clcsock->ops->setsockopt))
@@ -3067,7 +3065,6 @@ int smc_setsockopt(struct socket *sock,
 		sk->sk_err = smc->clcsock->sk->sk_err;
 		sk_error_report(sk);
 	}
-	mutex_unlock(&smc->clcsock_release_lock);
 
 	if (optlen < sizeof(int))
 		return -EINVAL;
@@ -3133,19 +3130,15 @@ int smc_getsockopt(struct socket *sock,
 		return __smc_getsockopt(sock, level, optname, optval, optlen);
 
 	smc = smc_sk(sock->sk);
-	mutex_lock(&smc->clcsock_release_lock);
 	if (!smc->clcsock) {
-		mutex_unlock(&smc->clcsock_release_lock);
 		return -EBADF;
 	}
 	/* socket options apply to the CLC socket */
 	if (unlikely(!smc->clcsock->ops->getsockopt)) {
-		mutex_unlock(&smc->clcsock_release_lock);
 		return -EOPNOTSUPP;
 	}
 	rc = smc->clcsock->ops->getsockopt(smc->clcsock, level, optname,
 					   optval, optlen);
-	mutex_unlock(&smc->clcsock_release_lock);
 	return rc;
 }
 
--

Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com
Tested-by: syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com

Tested on:

commit:         d521db38 Merge branch 'net-switch-back-to-struct-platf..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=167bd380580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f95955e3f7b5790c
dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13f0bbd0580000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[Pablo Neira Ayuso]

Cc'ing SMC maintainers.

syzkaller combining layer is a crazy way to find crashes.

I think this is a false possible lockdep considers smc->clcsock_release_lock
is a lock of the same class sk_lock-AF_INET.

this can be solved with lockdep_set_class in af_smc?

Thanks.

On Mon, Sep 23, 2024 at 08:46:24AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15d39e9f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=37c006d80708398d
> dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16215ca9980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/80466d230dfb/disk-94106455.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ba253eabab42/vmlinux-94106455.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/569982fb6c88/bzImage-94106455.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com
> 
> IPVS: Unknown mcast interface: macvlan0
> netlink: 8 bytes leftover after parsing attributes in process `syz-executor297'.
> netlink: 24 bytes leftover after parsing attributes in process `syz-executor297'.
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.11.0-syzkaller-01458-g9410645520e9 #0 Not tainted
> ------------------------------------------------------
> syz-executor297/5243 is trying to acquire lock:
> ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
> ffff88801cf99158 (sk_lock-AF_INET){+.+.}-{0:0}, at: gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674
> 
> but task is already holding lock:
> ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
> ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #2 (rtnl_mutex){+.+.}-{3:3}:
>        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>        __mutex_lock_common kernel/locking/mutex.c:608 [inline]
>        __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
>        start_sync_thread+0xdc/0x2dc0 net/netfilter/ipvs/ip_vs_sync.c:1761
>        do_ip_vs_set_ctl+0x442/0x13d0 net/netfilter/ipvs/ip_vs_ctl.c:2732
>        nf_setsockopt+0x295/0x2c0 net/netfilter/nf_sockopt.c:101
>        smc_setsockopt+0x275/0xe50 net/smc/af_smc.c:3064
>        do_sock_setsockopt+0x3af/0x720 net/socket.c:2330
>        __sys_setsockopt+0x1ae/0x250 net/socket.c:2353
>        __do_sys_setsockopt net/socket.c:2362 [inline]
>        __se_sys_setsockopt net/socket.c:2359 [inline]
>        __x64_sys_setsockopt+0xb5/0xd0 net/socket.c:2359
>        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>        entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> -> #1 (&smc->clcsock_release_lock){+.+.}-{3:3}:
>        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>        __mutex_lock_common kernel/locking/mutex.c:608 [inline]
>        __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
>        smc_switch_to_fallback+0x35/0xdb0 net/smc/af_smc.c:902
>        smc_sendmsg+0x11f/0x530 net/smc/af_smc.c:2771
>        sock_sendmsg_nosec net/socket.c:730 [inline]
>        __sock_sendmsg+0x221/0x270 net/socket.c:745
>        ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
>        ___sys_sendmsg net/socket.c:2657 [inline]
>        __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
>        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>        entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> -> #0 (sk_lock-AF_INET){+.+.}-{0:0}:
>        check_prev_add kernel/locking/lockdep.c:3133 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3252 [inline]
>        validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
>        __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
>        lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>        lock_sock_nested+0x48/0x100 net/core/sock.c:3611
>        lock_sock include/net/sock.h:1609 [inline]
>        gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674
>        gtp_encap_enable drivers/net/gtp.c:1707 [inline]
>        gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511
>        rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
>        __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
>        rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743
>        rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646
>        netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
>        netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>        netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
>        netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
>        sock_sendmsg_nosec net/socket.c:730 [inline]
>        __sock_sendmsg+0x221/0x270 net/socket.c:745
>        ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
>        ___sys_sendmsg net/socket.c:2657 [inline]
>        __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
>        do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>        do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>        entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> other info that might help us debug this:
> 
> Chain exists of:
>   sk_lock-AF_INET --> &smc->clcsock_release_lock --> rtnl_mutex
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   lock(rtnl_mutex);
>                                lock(&smc->clcsock_release_lock);
>                                lock(rtnl_mutex);
>   lock(sk_lock-AF_INET);
> 
>  *** DEADLOCK ***
> 
> 1 lock held by syz-executor297/5243:
>  #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
>  #0: ffffffff8fc88588 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x6e6/0xcf0 net/core/rtnetlink.c:6643
> 
> stack backtrace:
> CPU: 0 UID: 0 PID: 5243 Comm: syz-executor297 Not tainted 6.11.0-syzkaller-01458-g9410645520e9 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:93 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
>  check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2186
>  check_prev_add kernel/locking/lockdep.c:3133 [inline]
>  check_prevs_add kernel/locking/lockdep.c:3252 [inline]
>  validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868
>  __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142
>  lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>  lock_sock_nested+0x48/0x100 net/core/sock.c:3611
>  lock_sock include/net/sock.h:1609 [inline]
>  gtp_encap_enable_socket+0x2ce/0x5c0 drivers/net/gtp.c:1674
>  gtp_encap_enable drivers/net/gtp.c:1707 [inline]
>  gtp_newlink+0x589/0xf30 drivers/net/gtp.c:1511
>  rtnl_newlink_create net/core/rtnetlink.c:3510 [inline]
>  __rtnl_newlink net/core/rtnetlink.c:3730 [inline]
>  rtnl_newlink+0x1591/0x20a0 net/core/rtnetlink.c:3743
>  rtnetlink_rcv_msg+0x73f/0xcf0 net/core/rtnetlink.c:6646
>  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2550
>  netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline]
>  netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1357
>  netlink_sendmsg+0x8e4/0xcb0 net/netlink/af_netlink.c:1901
>  sock_sendmsg_nosec net/socket.c:730 [inline]
>  __sock_sendmsg+0x221/0x270 net/socket.c:745
>  ____sys_sendmsg+0x525/0x7d0 net/socket.c:2603
>  ___sys_sendmsg net/socket.c:2657 [inline]
>  __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2686
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fed198844a9
> Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RS
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup

Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[syzbot]

syzbot suspects this issue was fixed by commit:

commit 752e2217d789be2c6a6ac66554b981cd71cd9f31
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Mon Apr 7 17:03:17 2025 +0000

    smc: Fix lockdep false-positive for IPPROTO_SMC.

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=140462f4580000
start commit:   9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel..
git tree:       net-next
kernel config:  https://syzkaller.appspot.com/x/.config?x=37c006d80708398d
dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16215ca9980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: smc: Fix lockdep false-positive for IPPROTO_SMC.

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [net?] possible deadlock in gtp_encap_enable_socket

[Kuniyuki Iwashima]

From: syzbot <syzbot+e953a8f3071f5c0a28fd@syzkaller.appspotmail.com>
Date: Mon, 12 May 2025 09:08:04 -0700
> syzbot suspects this issue was fixed by commit:
> 
> commit 752e2217d789be2c6a6ac66554b981cd71cd9f31
> Author: Kuniyuki Iwashima <kuniyu@amazon.com>
> Date:   Mon Apr 7 17:03:17 2025 +0000
> 
>     smc: Fix lockdep false-positive for IPPROTO_SMC.
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=140462f4580000
> start commit:   9410645520e9 Merge tag 'net-next-6.12' of git://git.kernel..
> git tree:       net-next
> kernel config:  https://syzkaller.appspot.com/x/.config?x=37c006d80708398d
> dashboard link: https://syzkaller.appspot.com/bug?extid=e953a8f3071f5c0a28fd
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16215ca9980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=110c6c27980000
> 
> If the result looks correct, please mark the issue as fixed by replying with:
> 
> #syz fix: smc: Fix lockdep false-positive for IPPROTO_SMC.

#syz fix: smc: Fix lockdep false-positive for IPPROTO_SMC.

Re: [syzbot] test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: test
Author: danielyangkang@gmail.com

#syz test

Re: [syzbot] Test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Test
Author: radoslaw.zielonek@gmail.com

#syz test 

---
 include/linux/sched.h |  7 +++++++
 kernel/sched/core.c   |  1 +
 kernel/sched/rt.c     | 26 +++++++++++++++++++++++---
 kernel/signal.c       |  9 +++++++++
 4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
 	size_t				sas_ss_size;
 	unsigned int			sas_ss_flags;
 
+	/*
+	 * Number of signals received by an RT task between scheduling ticks.
+	 * This counter is used to throttle RT tasks when too many signals
+	 * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+	 */
+	atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
 	struct callback_head		*task_works;
 
 #ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 			p->policy = SCHED_NORMAL;
 			p->static_prio = NICE_TO_PRIO(0);
 			p->rt_priority = 0;
+			atomic_set(&p->rt_signals_recv_count, 0);
 		} else if (PRIO_TO_NICE(p->static_prio) < 0)
 			p->static_prio = NICE_TO_PRIO(0);
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
  */
 int sysctl_sched_rt_runtime = 950000;
 
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
 #ifdef CONFIG_SYSCTL
 static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 	return rt_task_of(rt_se)->prio;
 }
 
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
 {
 	u64 runtime = sched_rt_runtime(rt_rq);
 
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 	if (runtime == RUNTIME_INF)
 		return 0;
 
-	if (rt_rq->rt_time > runtime) {
+	/*
+	 * When a large number of signals are sent to this task (e.g., POSIX timers)
+	 * the delta time deviates significantly from real time due to the overhead
+	 * of handling signals. For RT tasks, this can cause an RCU stall.
+	 * To avoid this, throttle the task when the number of signals received
+	 * exceeds a certain threshold.
+	 */
+	if (rt_rq->rt_time > runtime ||
+		rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
 		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 
 		/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
 		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 			raw_spin_lock(&rt_rq->rt_runtime_lock);
 			rt_rq->rt_time += delta_exec;
-			exceeded = sched_rt_runtime_exceeded(rt_rq);
+			exceeded = sched_rt_runtime_exceeded(
+						rt_rq,
+						atomic_read(&curr->rt_signals_recv_count));
 			if (exceeded)
 				resched_curr(rq);
 			raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
 				do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
 		}
 	}
+	atomic_set(&curr->rt_signals_recv_count, 0);
 }
 
 static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
 	bool resched_timer = false;
 	int signr;
 
+	/*
+	 * To prevent an RCU stall due to receiving too many signals by RT tasks,
+	 * count all signals regardless of their type.
+	 * Based on this counter, the RT scheduler will decide whether the task
+	 * should be throttled or not.
+	 */
+	if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+		atomic_inc(&tsk->rt_signals_recv_count);
+
 	/* We only dequeue private signals from ourselves, we don't let
 	 * signalfd steal them
 	 */
-- 
2.43.0

Re: [syzbot] Test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Test
Author: radoslaw.zielonek@gmail.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git dccb07f2914cdab2ac3a5b6c98406f765acab803

---
 include/linux/sched.h |  7 +++++++
 kernel/sched/core.c   |  1 +
 kernel/sched/rt.c     | 26 +++++++++++++++++++++++---
 kernel/signal.c       |  9 +++++++++
 4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
 	size_t				sas_ss_size;
 	unsigned int			sas_ss_flags;
 
+	/*
+	 * Number of signals received by an RT task between scheduling ticks.
+	 * This counter is used to throttle RT tasks when too many signals
+	 * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+	 */
+	atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
 	struct callback_head		*task_works;
 
 #ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 			p->policy = SCHED_NORMAL;
 			p->static_prio = NICE_TO_PRIO(0);
 			p->rt_priority = 0;
+			atomic_set(&p->rt_signals_recv_count, 0);
 		} else if (PRIO_TO_NICE(p->static_prio) < 0)
 			p->static_prio = NICE_TO_PRIO(0);
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
  */
 int sysctl_sched_rt_runtime = 950000;
 
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
 #ifdef CONFIG_SYSCTL
 static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 	return rt_task_of(rt_se)->prio;
 }
 
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
 {
 	u64 runtime = sched_rt_runtime(rt_rq);
 
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 	if (runtime == RUNTIME_INF)
 		return 0;
 
-	if (rt_rq->rt_time > runtime) {
+	/*
+	 * When a large number of signals are sent to this task (e.g., POSIX timers)
+	 * the delta time deviates significantly from real time due to the overhead
+	 * of handling signals. For RT tasks, this can cause an RCU stall.
+	 * To avoid this, throttle the task when the number of signals received
+	 * exceeds a certain threshold.
+	 */
+	if (rt_rq->rt_time > runtime ||
+		rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
 		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 
 		/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
 		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 			raw_spin_lock(&rt_rq->rt_runtime_lock);
 			rt_rq->rt_time += delta_exec;
-			exceeded = sched_rt_runtime_exceeded(rt_rq);
+			exceeded = sched_rt_runtime_exceeded(
+						rt_rq,
+						atomic_read(&curr->rt_signals_recv_count));
 			if (exceeded)
 				resched_curr(rq);
 			raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
 				do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
 		}
 	}
+	atomic_set(&curr->rt_signals_recv_count, 0);
 }
 
 static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
 	bool resched_timer = false;
 	int signr;
 
+	/*
+	 * To prevent an RCU stall due to receiving too many signals by RT tasks,
+	 * count all signals regardless of their type.
+	 * Based on this counter, the RT scheduler will decide whether the task
+	 * should be throttled or not.
+	 */
+	if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+		atomic_inc(&tsk->rt_signals_recv_count);
+
 	/* We only dequeue private signals from ourselves, we don't let
 	 * signalfd steal them
 	 */
-- 
2.43.0

Re: [syzbot] Test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Test
Author: radoslaw.zielonek@gmail.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fe46a7dd189e25604716c03576d05ac8a5209743

---
 include/linux/sched.h |  7 +++++++
 kernel/sched/core.c   |  1 +
 kernel/sched/rt.c     | 26 +++++++++++++++++++++++---
 kernel/signal.c       |  9 +++++++++
 4 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
 	size_t				sas_ss_size;
 	unsigned int			sas_ss_flags;
 
+	/*
+	 * Number of signals received by an RT task between scheduling ticks.
+	 * This counter is used to throttle RT tasks when too many signals
+	 * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+	 */
+	atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
 	struct callback_head		*task_works;
 
 #ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 			p->policy = SCHED_NORMAL;
 			p->static_prio = NICE_TO_PRIO(0);
 			p->rt_priority = 0;
+			atomic_set(&p->rt_signals_recv_count, 0);
 		} else if (PRIO_TO_NICE(p->static_prio) < 0)
 			p->static_prio = NICE_TO_PRIO(0);
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
  */
 int sysctl_sched_rt_runtime = 950000;
 
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
 #ifdef CONFIG_SYSCTL
 static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
 static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 	return rt_task_of(rt_se)->prio;
 }
 
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
 {
 	u64 runtime = sched_rt_runtime(rt_rq);
 
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 	if (runtime == RUNTIME_INF)
 		return 0;
 
-	if (rt_rq->rt_time > runtime) {
+	/*
+	 * When a large number of signals are sent to this task (e.g., POSIX timers)
+	 * the delta time deviates significantly from real time due to the overhead
+	 * of handling signals. For RT tasks, this can cause an RCU stall.
+	 * To avoid this, throttle the task when the number of signals received
+	 * exceeds a certain threshold.
+	 */
+	if (rt_rq->rt_time > runtime ||
+		rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
 		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 
 		/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
 		if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 			raw_spin_lock(&rt_rq->rt_runtime_lock);
 			rt_rq->rt_time += delta_exec;
-			exceeded = sched_rt_runtime_exceeded(rt_rq);
+			exceeded = sched_rt_runtime_exceeded(
+						rt_rq,
+						atomic_read(&curr->rt_signals_recv_count));
 			if (exceeded)
 				resched_curr(rq);
 			raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
 				do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
 		}
 	}
+	atomic_set(&curr->rt_signals_recv_count, 0);
 }
 
 static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
 	bool resched_timer = false;
 	int signr;
 
+	/*
+	 * To prevent an RCU stall due to receiving too many signals by RT tasks,
+	 * count all signals regardless of their type.
+	 * Based on this counter, the RT scheduler will decide whether the task
+	 * should be throttled or not.
+	 */
+	if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+		atomic_inc(&tsk->rt_signals_recv_count);
+
 	/* We only dequeue private signals from ourselves, we don't let
 	 * signalfd steal them
 	 */
-- 
2.43.0

Re: [syzbot] test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: test
Author: mukattreyee@gmail.com

#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Re: [syzbot] Test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

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Subject: Test
Author: radoslaw.zielonek@gmail.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 71b1543c83d65af8215d7558d70fc2ecbee77dcf

---
 net/sched/sch_taprio.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index a0d54b422186..41add4a1d407 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -44,6 +44,8 @@ static struct static_key_false taprio_have_working_mqprio;
 	(TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST | TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD)
 #define TAPRIO_FLAGS_INVALID U32_MAX
 
+#define TAPRIO_MAX_NUM_SCHEDULES_BEFORE_NOW 10
+
 struct sched_entry {
 	/* Durations between this GCL entry and the GCL entry where the
 	 * respective traffic class gate closes
@@ -62,6 +64,8 @@ struct sched_entry {
 	u32 gate_mask;
 	u32 interval;
 	u8 command;
+	/* Used to skip some cycles to prevent other tasks from starving */
+	u8 num_schedules_before_now;
 };
 
 struct sched_gate_list {
@@ -111,6 +115,9 @@ struct __tc_taprio_qopt_offload {
 	struct tc_taprio_qopt_offload offload;
 };
 
+static void setup_txtime(struct taprio_sched *q,
+			 struct sched_gate_list *sched, ktime_t base);
+
 static void taprio_calculate_gate_durations(struct taprio_sched *q,
 					    struct sched_gate_list *sched)
 {
@@ -919,6 +926,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 	struct sched_entry *entry, *next;
 	struct Qdisc *sch = q->root;
 	ktime_t end_time;
+	ktime_t basenow;
 	int tc;
 
 	spin_lock(&q->current_entry_lock);
@@ -977,6 +985,23 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 	taprio_set_budgets(q, oper, next);
 
 first_run:
+	basenow = ktime_get();
+	if (ktime_before(end_time, basenow))
+	{
+		next->num_schedules_before_now++;
+		if (next->num_schedules_before_now >= TAPRIO_MAX_NUM_SCHEDULES_BEFORE_NOW)
+		{
+			end_time = ktime_add_ns(basenow, oper->cycle_time);
+			next->end_time = end_time;
+			next->num_schedules_before_now = 0;
+			setup_txtime(q, oper, basenow);
+		}
+	}
+	else
+	{
+		next->num_schedules_before_now = 0;
+	}
+
 	rcu_assign_pointer(q->current_entry, next);
 	spin_unlock(&q->current_entry_lock);
 
@@ -1074,6 +1099,7 @@ static int parse_sched_entry(struct taprio_sched *q, struct nlattr *n,
 	}
 
 	entry->index = index;
+	entry->num_schedules_before_now = 0;
 
 	return fill_sched_entry(q, tb, entry, extack);
 }
-- 
2.43.0

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