[syzbot] [net?] KMSAN: uninit-value in __inet_bind

[syzbot] [net?] KMSAN: uninit-value in __inet_bind

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cd7a5651db26 alpha: add missing address argument in call t..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11bc7e5a580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=50148b563a4d5941
dashboard link: https://syzkaller.appspot.com/bug?extid=aae646f09192f72a68dc
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122c0652580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14f7e15a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/23c623fcb1bf/disk-cd7a5651.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5128bb44f38d/vmlinux-cd7a5651.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a65d6b263e08/bzImage-cd7a5651.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com

wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
=====================================================
BUG: KMSAN: uninit-value in __inet_bind+0x8a4/0xf20 net/ipv4/af_inet.c:511
 __inet_bind+0x8a4/0xf20 net/ipv4/af_inet.c:511
 inet_bind_sk net/ipv4/af_inet.c:464 [inline]
 inet_bind+0x12c/0x1a0 net/ipv4/af_inet.c:469
 kernel_bind+0xd6/0x130 net/socket.c:3554
 rds_tcp_conn_path_connect+0x952/0xff0 net/rds/tcp_connect.c:175
 rds_connect_worker+0x353/0x4d0 net/rds/threads.c:176
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xae7/0x1d60 kernel/workqueue.c:3358
 worker_thread+0xede/0x1580 kernel/workqueue.c:3439
 kthread+0x53f/0x600 kernel/kthread.c:467
 ret_from_fork+0x20f/0x910 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was stored to memory at:
 kernel_bind+0x92/0x130 net/socket.c:3552
 rds_tcp_conn_path_connect+0x952/0xff0 net/rds/tcp_connect.c:175
 rds_connect_worker+0x353/0x4d0 net/rds/threads.c:176
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xae7/0x1d60 kernel/workqueue.c:3358
 worker_thread+0xede/0x1580 kernel/workqueue.c:3439
 kthread+0x53f/0x600 kernel/kthread.c:467
 ret_from_fork+0x20f/0x910 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was stored to memory at:
 rds_tcp_conn_path_connect+0xaf8/0xff0 net/rds/tcp_connect.c:174
 rds_connect_worker+0x353/0x4d0 net/rds/threads.c:176
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xae7/0x1d60 kernel/workqueue.c:3358
 worker_thread+0xede/0x1580 kernel/workqueue.c:3439
 kthread+0x53f/0x600 kernel/kthread.c:467
 ret_from_fork+0x20f/0x910 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4466 [inline]
 slab_alloc_node mm/slub.c:4788 [inline]
 kmem_cache_alloc_noprof+0x373/0x1200 mm/slub.c:4795
 rds_tcp_conn_alloc+0x7b/0xbb0 net/rds/tcp.c:376
 __rds_conn_create+0x267f/0x34e0 net/rds/connection.c:283
 rds_conn_create_outgoing+0x5d/0x80 net/rds/connection.c:377
 rds_sendmsg+0x2684/0x4d70 net/rds/send.c:1321
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xfe7/0x1080 net/socket.c:2592
 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x211/0x3e0 net/socket.c:2681
 x64_sys_call+0x1e20/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 1096 Comm: kworker/u8:7 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: krds_cp_wq#0/0 rds_connect_worker
=====================================================


---
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Forwarded: Re: [syzbot] [net?] KMSAN: uninit-value in __inet_bind

[syzbot]

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***

Subject: Re: [syzbot] [net?] KMSAN: uninit-value in __inet_bind
Author: tabreztalks@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git main

From 42a8555a679994cc8113267b7ba08af054a48852 Mon Sep 17 00:00:00 2001
From: Tabrez Ahmed <tabreztalks@gmail.com>
Date: Sun, 15 Feb 2026 11:24:13 +0530
Subject: [PATCH net] rds: tcp: fix uninit-value in __inet_bind

KMSAN reported an uninit-value access in __inet_bind() when binding
an RDS TCP socket. The uninitialized memory originates from
rds_tcp_conn_alloc(), which uses kmem_cache_alloc() to allocate the
rds_tcp_connection structure.

The structure is not zero-initialized, leaving random data in its fields.
When the networking stack later tries to bind the socket using these
dirty values, KMSAN flags the uninitialized access.

Fix this by using kmem_cache_zalloc() instead of kmem_cache_alloc() to
ensure the structure is zeroed out upon allocation.

Reported-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=aae646f09192f72a68dc
Fixes: 70041088e3b9 ("RDS: Add TCP transport to RDS")

Signed-off-by: Tabrez Ahmed <tabreztalks@gmail.com>
---
 net/rds/tcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 45484a93d75f..04f310255692 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -373,7 +373,7 @@ static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp)
 	int ret = 0;
 
 	for (i = 0; i < RDS_MPATH_WORKERS; i++) {
-		tc = kmem_cache_alloc(rds_tcp_conn_slab, gfp);
+		tc = kmem_cache_zalloc(rds_tcp_conn_slab, gfp);
 		if (!tc) {
 			ret = -ENOMEM;
 			goto fail;
-- 
2.43.0

Re: [syzbot] [net?] KMSAN: uninit-value in __inet_bind

[syzbot]

Hello,

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

Reported-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com
Tested-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com

Tested on:

commit:         ee5492fd fbnic: close fw_log race between users and te..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git main
console output: https://syzkaller.appspot.com/x/log.txt?x=1282c722580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c4b32638806e00b5
dashboard link: https://syzkaller.appspot.com/bug?extid=aae646f09192f72a68dc
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=152feb3a580000

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