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blk_mq_complete_request_remote From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [syzbot] [block?] BUG: unable to handle kernel paging request in blk_mq_complete_request_remote Author: nenkov2004@gmail.com #syz test: https://github.com/torvalds/linux.git 58c1eb84e97701c583605ba2fd553b69afba2245 On Tue, 10 Nov 2026 13:49:04 -0800, syzbot wrote: > Hello, > > syzbot has tested the proposed patch but the reproducer is still triggering an issue: > KASAN: null-ptr-deref Write in fib_insert_alias > > ================================================================== > BUG: KASAN: null-ptr-deref in hlist_add_before_rcu include/linux/rculist.h:744 [inline] > BUG: KASAN: null-ptr-deref in fib_insert_alias+0xb0/0xb08 net/ipv4/fib_trie.c:1160 > Write of size 8 at addr 0000000000000000 by task syz-executor/5244 > > CPU: 1 UID: 0 PID: 5244 Comm: syz-executor Not tainted syzkaller #0 PREEMPT > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 > Call trace: > show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) > __dump_stack+0x30/0x40 lib/dump_stack.c:94 > dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 > print_report+0x58/0x84 mm/kasan/report.c:485 > kasan_report+0x8c/0xc4 mm/kasan/report.c:595 > check_region_inline mm/kasan/generic.c:-1 [inline] > kasan_check_range+0x17c/0x1ac mm/kasan/generic.c:200 > __kasan_check_write+0x20/0x30 mm/kasan/shadow.c:37 > hlist_add_before_rcu include/linux/rculist.h:744 [inline] > fib_insert_alias+0xb0/0xb08 net/ipv4/fib_trie.c:1160 > fib_table_insert+0x5dc/0x12bc net/ipv4/fib_trie.c:1352 > fib_magic+0x26c/0x344 net/ipv4/fib_frontend.c:1147 > fib_add_ifaddr+0x2e0/0x500 net/ipv4/fib_frontend.c:1184 > fib_netdev_event+0x35c/0x49c net/ipv4/fib_frontend.c:1529 > notifier_call_chain+0x1a4/0x4cc kernel/notifier.c:86 > raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:558 > call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2313 > call_netdevice_notifiers_extack net/core/dev.c:2351 [inline] > call_netdevice_notifiers net/core/dev.c:2365 [inline] > __dev_notify_flags+0x288/0x438 net/core/dev.c:10051 > netif_change_flags+0xd0/0x15c net/core/dev.c:10080 > do_setlink+0xc28/0x32d4 net/core/rtnetlink.c:3294 > rtnl_changelink net/core/rtnetlink.c:3942 [inline] > __rtnl_newlink net/core/rtnetlink.c:4113 [inline] > rtnl_newlink+0xf48/0x1390 net/core/rtnetlink.c:4252 > rtnetlink_rcv_msg+0x66c/0x9bc net/core/rtnetlink.c:7169 > netlink_rcv_skb+0x238/0x414 net/netlink/af_netlink.c:2584 > rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:7196 > netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline] > netlink_unicast+0x73c/0x934 net/netlink/af_netlink.c:1361 > netlink_sendmsg+0x670/0x98c net/netlink/af_netlink.c:1920 > sock_sendmsg_nosec net/socket.c:800 [inline] > __sock_sendmsg+0xc8/0x188 net/socket.c:818 > __sys_sendto+0x250/0x328 net/socket.c:2283 > __do_sys_sendto net/socket.c:2290 [inline] > __se_sys_sendto net/socket.c:2286 [inline] > __arm64_sys_sendto+0xec/0x10c net/socket.c:2286 > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] > invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 > el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 > do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 > el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:797 > el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:816 > el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 > ================================================================== > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 > Mem abort info: > ESR = 0x0000000096000044 > EC = 0x25: DABT (current EL), IL = 32 bits > SET = 0, FnV = 0 > EA = 0, S1PTW = 0 > FSC = 0x04: level 0 translation fault > Data abort info: > ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000 > CM = 0, WnR = 1, TnD = 0, TagAccess = 0 > GCS = 0, Overlay = 0, DirtyBit = 0 > user pgtable: 4k pages, 48-bit VAs, pgdp=00000001173dd000 > [0000000000000000] pgd=0000000000000000, p4d=0000000000000000 > Internal error: Oops: 0000000096000044 [#1] SMP > Modules linked in: > CPU: 1 UID: 0 PID: 5244 Comm: syz-executor Tainted: G B syzkaller #0 PREEMPT > Tainted: [B]=BAD_PAGE > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 > pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) > pc : hlist_add_before_rcu include/linux/rculist.h:744 [inline] > pc : fib_insert_alias+0xb0/0xb08 net/ipv4/fib_trie.c:1160 > lr : hlist_add_before_rcu include/linux/rculist.h:744 [inline] > lr : fib_insert_alias+0xb0/0xb08 net/ipv4/fib_trie.c:1160 > sp : ffff800096b86750 > x29: ffff800096b86780 x28: ffff0000c8fb8528 x27: ffff0000eb35fc20 > x26: dfff800000000000 x25: 0000000000000018 x24: ffff0000c8fb8210 > x23: ffff0000dcc87660 x22: 0000000000000000 x21: ffff0000c8fb8528 > x20: ffff0000c8fb8218 x19: 1fffe000191f7043 x18: 0000000000000000 > x17: 3d3d3d3d3d3d3d3d x16: 3d3d3d3d3d3d3d3d x15: 3d3d3d3d3d3d3d3d > x14: 00000000000006f9 x13: 0000000000000001 x12: 0000000000000000 > x11: 0000000000000000 x10: ffff70001161f92d x9 : 0000000000000000 > x8 : 0000000000000000 x7 : 0000000000000000 x6 : ffff8000804a0c38 > x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff80008030c9a8 > x2 : 0000000000000000 x1 : ffff0000c1fb1d80 x0 : 0000000000000000 > Call trace: > hlist_add_before_rcu include/linux/rculist.h:744 [inline] (P) > fib_insert_alias+0xb0/0xb08 net/ipv4/fib_trie.c:1160 (P) > fib_table_insert+0x5dc/0x12bc net/ipv4/fib_trie.c:1352 > fib_magic+0x26c/0x344 net/ipv4/fib_frontend.c:1147 > fib_add_ifaddr+0x2e0/0x500 net/ipv4/fib_frontend.c:1184 > fib_netdev_event+0x35c/0x49c net/ipv4/fib_frontend.c:1529 > notifier_call_chain+0x1a4/0x4cc kernel/notifier.c:86 > raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:558 > call_netdevice_notifiers_info+0xb8/0x120 net/core/dev.c:2313 > call_netdevice_notifiers_extack net/core/dev.c:2351 [inline] > call_netdevice_notifiers net/core/dev.c:2365 [inline] > __dev_notify_flags+0x288/0x438 net/core/dev.c:10051 > netif_change_flags+0xd0/0x15c net/core/dev.c:10080 > do_setlink+0xc28/0x32d4 net/core/rtnetlink.c:3294 > rtnl_changelink net/core/rtnetlink.c:3942 [inline] > __rtnl_newlink net/core/rtnetlink.c:4113 [inline] > rtnl_newlink+0xf48/0x1390 net/core/rtnetlink.c:4252 > rtnetlink_rcv_msg+0x66c/0x9bc net/core/rtnetlink.c:7169 > netlink_rcv_skb+0x238/0x414 net/netlink/af_netlink.c:2584 > rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:7196 > netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline] > netlink_unicast+0x73c/0x934 net/netlink/af_netlink.c:1361 > netlink_sendmsg+0x670/0x98c net/netlink/af_netlink.c:1920 > sock_sendmsg_nosec net/socket.c:800 [inline] > __sock_sendmsg+0xc8/0x188 net/socket.c:818 > __sys_sendto+0x250/0x328 net/socket.c:2283 > __do_sys_sendto net/socket.c:2290 [inline] > __se_sys_sendto net/socket.c:2286 [inline] > __arm64_sys_sendto+0xec/0x10c net/socket.c:2286 > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] > invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 > el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 > do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 > el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:797 > el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:816 > el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 > Code: aa1603e0 52800101 f90002b8 96d8b07a (c89ffed5) > ---[ end trace 0000000000000000 ]--- > ---------------- > Code disassembly (best guess): > 0: aa1603e0 mov x0, x22 > 4: 52800101 mov w1, #0x8 // #8 > 8: f90002b8 str x24, [x21] > c: 96d8b07a bl 0xfffffffffb62c1f4 > * 10: c89ffed5 stlr x21, [x22] <-- trapping instruction > > Tested on: > > commit: 067c5c24 Merge tag 'page_alloc-for-7.4-rc2' of git://g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=12c7b1fd580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=c06331d9bb9c8204 > dashboard link: https://syzkaller.appspot.com/bug?extid=2e3bf0bd49acd9b21d4b > compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 > userspace arch: arm64 > patch: https://syzkaller.appspot.com/x/patch.diff?x=16dccebe580000