[moderation] [input?] KCSAN: data-race in evdev_pass_values / evdev_read (13)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a66191c590b3 Merge tag 'hyperv-fixes-signed-20260121' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16fa0bfa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c9e86480ac654d3
dashboard link: https://syzkaller.appspot.com/bug?extid=1b327485934adf39955b
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [dmitry....@gmail.com linux...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/47495cf87c20/disk-a66191c5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2ddc7273c432/vmlinux-a66191c5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/45267480b20c/bzImage-a66191c5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1b3274...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in evdev_pass_values / evdev_read

write to 0xffff888104842008 of 4 bytes by task 8439 on cpu 1:
__pass_event drivers/input/evdev.c:239 [inline]
evdev_pass_values+0x387/0x4e0 drivers/input/evdev.c:278
evdev_events+0x8e/0xd0 drivers/input/evdev.c:306
input_pass_values+0x123/0x390 drivers/input/input.c:128
input_event_dispose+0x248/0x320 drivers/input/input.c:342
input_handle_event+0x9e8/0xa20 drivers/input/input.c:370
input_inject_event+0xbc/0x120 drivers/input/input.c:424
evdev_write+0x224/0x2b0 drivers/input/evdev.c:528
vfs_write+0x269/0x9f0 fs/read_write.c:684
ksys_write+0xdc/0x1a0 fs/read_write.c:738
__do_sys_write fs/read_write.c:749 [inline]
__se_sys_write fs/read_write.c:746 [inline]
__x64_sys_write+0x40/0x50 fs/read_write.c:746
x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104842008 of 4 bytes by task 2991 on cpu 0:
evdev_read+0x157/0x5e0 drivers/input/evdev.c:572
vfs_read+0x1ab/0x7f0 fs/read_write.c:570
ksys_read+0xdc/0x1a0 fs/read_write.c:715
__do_sys_read fs/read_write.c:724 [inline]
__se_sys_read fs/read_write.c:722 [inline]
__x64_sys_read+0x40/0x50 fs/read_write.c:722
x64_sys_call+0x2889/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000002 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2991 Comm: acpid Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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