[moderation] [lsm?] [keyrings?] KCSAN: data-race in search_nested_keyrings / search_nested_keyrings (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9dd1835ecda5 Merge tag 'dma-mapping-6.17-2025-09-09' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11287562580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=234a604530f174fff108
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [dhow...@redhat.com jar...@kernel.org jmo...@namei.org keyr...@vger.kernel.org linux-...@vger.kernel.org linux-secu...@vger.kernel.org pa...@paul-moore.com se...@hallyn.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bed60878f1bb/disk-9dd1835e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7a737ddc0fed/vmlinux-9dd1835e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/39c2c269c318/bzImage-9dd1835e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+234a60...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in search_nested_keyrings / search_nested_keyrings

write to 0xffff888103569860 of 8 bytes by task 8552 on cpu 1:
search_nested_keyrings+0x79a/0x9b0 security/keys/keyring.c:859
keyring_search_rcu+0xf7/0x190 security/keys/keyring.c:925
get_user_session_keyring_rcu security/keys/process_keys.c:208 [inline]
search_cred_keyrings_rcu+0x2a3/0x3c0 security/keys/process_keys.c:500
search_process_keyrings_rcu security/keys/process_keys.c:544 [inline]
lookup_user_key+0x8eb/0xd10 security/keys/process_keys.c:762
__do_sys_add_key security/keys/keyctl.c:126 [inline]
__se_sys_add_key+0x263/0x350 security/keys/keyctl.c:74
__x64_sys_add_key+0x67/0x80 security/keys/keyctl.c:74
x64_sys_call+0x28c4/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:249
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff888103569860 of 8 bytes by task 8550 on cpu 0:
search_nested_keyrings+0x79a/0x9b0 security/keys/keyring.c:859
keyring_search_rcu+0xf7/0x190 security/keys/keyring.c:925
keyring_search+0x135/0x1a0 security/keys/keyring.c:967
look_up_user_keyrings+0x287/0x400 security/keys/process_keys.c:124
lookup_user_key+0x563/0xd10 security/keys/process_keys.c:704
keyctl_keyring_move+0x75/0x110 security/keys/keyctl.c:608
__do_sys_keyctl security/keys/keyctl.c:2012 [inline]
__se_sys_keyctl+0x5f7/0xb80 security/keys/keyctl.c:1874
__x64_sys_keyctl+0x67/0x80 security/keys/keyctl.c:1874
x64_sys_call+0x2f6d/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:251
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000068c1110d -> 0x0000000068c1110e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 8550 Comm: syz.2.1718 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================
loop2: detected capacity change from 0 to 512
EXT4-fs (loop2): 1 orphan inode deleted
ext4 filesystem being mounted at /358/file1 supports timestamps until 2038-01-19 (0x7fffffff)


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