[moderation] [selinux?] KCSAN: data-race in selinux_cred_prepare / selinux_inode_permission (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e9a6fb0bcdd7 Linux 6.18-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17205412580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d2e0bc0ae94545f7
dashboard link: https://syzkaller.appspot.com/bug?extid=00a653d846b0a48a964b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [linux-...@vger.kernel.org omos...@redhat.com pa...@paul-moore.com sel...@vger.kernel.org stephen.sm...@gmail.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a4187a0f60fe/disk-e9a6fb0b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c8702ff2e21c/vmlinux-e9a6fb0b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/328a6a6a5005/bzImage-e9a6fb0b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+00a653...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in selinux_cred_prepare / selinux_inode_permission

write to 0xffff88811ac89c20 of 4 bytes by task 3652 on cpu 1:
task_avdcache_search security/selinux/hooks.c:3150 [inline]
selinux_inode_permission+0x3ac/0x740 security/selinux/hooks.c:3225
security_inode_permission+0x6d/0xb0 security/security.c:2363
inode_permission+0x106/0x310 fs/namei.c:601
may_lookup fs/namei.c:1858 [inline]
link_path_walk+0x162/0x900 fs/namei.c:2467
path_lookupat+0x63/0x2a0 fs/namei.c:2675
filename_lookup+0x147/0x340 fs/namei.c:2705
user_path_at+0x3e/0x130 fs/namei.c:3215
vfs_open_tree+0xef/0x530 fs/namespace.c:3094
__do_sys_open_tree fs/namespace.c:3109 [inline]
__se_sys_open_tree fs/namespace.c:3104 [inline]
__x64_sys_open_tree+0x45/0xc0 fs/namespace.c:3104
x64_sys_call+0x2a8b/0x3000 arch/x86/include/generated/asm/syscalls_64.h:429
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

read to 0xffff88811ac89c00 of 104 bytes by task 3651 on cpu 0:
selinux_cred_prepare+0x60/0x70 security/selinux/hooks.c:4167
security_prepare_creds+0xbb/0x120 security/security.c:3315
prepare_creds+0x34a/0x4c0 kernel/cred.c:242
__sys_setuid+0x67/0x310 kernel/sys.c:663
__do_sys_setuid kernel/sys.c:700 [inline]
__se_sys_setuid kernel/sys.c:698 [inline]
__x64_sys_setuid+0x1e/0x30 kernel/sys.c:698
x64_sys_call+0x1a84/0x3000 arch/x86/include/generated/asm/syscalls_64.h:106
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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3651 Comm: syz.0.57 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


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