linux-kernel - [syzbot] [pci?] KCSAN: data-race in vga_arb_write / vga_arb

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Message-ID: <678136f7.050a0220.216c54.0015.GAE@google.com>
Date: Fri, 10 Jan 2025 07:04:23 -0800
From: syzbot <syzbot+2699c160471dfeee2644@...kaller.appspotmail.com>
To: bhelgaas@...gle.com, linux-kernel@...r.kernel.org, 
	linux-pci@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [pci?] KCSAN: data-race in vga_arb_write / vga_arb_write (4)

Hello,

syzbot found the following issue on:

HEAD commit:    9b2ffa6148b1 Merge tag 'mtd/fixes-for-6.13-rc5' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12aac0b0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=87d3cfca6847d1fa
dashboard link: https://syzkaller.appspot.com/bug?extid=2699c160471dfeee2644
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8f3f5cceed80/disk-9b2ffa61.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ba00b70d91e/vmlinux-9b2ffa61.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b99c1bb4d63f/bzImage-9b2ffa61.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2699c160471dfeee2644@...kaller.appspotmail.com

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

read-write to 0xffff88814f612424 of 4 bytes by task 17707 on cpu 0:
 vga_arb_write+0x11fa/0x1410 drivers/pci/vgaarb.c:1204
 vfs_write+0x281/0x920 fs/read_write.c:677
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read-write to 0xffff88814f612424 of 4 bytes by task 17708 on cpu 1:
 vga_arb_write+0xf45/0x1410 drivers/pci/vgaarb.c:1263
 vfs_write+0x281/0x920 fs/read_write.c:677
 ksys_write+0xe8/0x1b0 fs/read_write.c:731
 __do_sys_write fs/read_write.c:742 [inline]
 __se_sys_write fs/read_write.c:739 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:739
 x64_sys_call+0x287e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000007

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17708 Comm: syz.4.3325 Not tainted 6.13.0-rc4-syzkaller-00012-g9b2ffa6148b1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


---
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