On Fri, 10 Jan 2025 at 16:04, syzbot <syzbot+2699c160471dfeee2644@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > 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@xxxxxxxxxxxxxxxxxxxxxxxxx This is a race between io_cnt++ and io_cnt--. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/vgaarb.c?id=9b2ffa6148b1e4468d08f7e0e7e371c43cac9ffe#n1204 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/vgaarb.c?id=9b2ffa6148b1e4468d08f7e0e7e371c43cac9ffe#n1263 Later io_cnt is used to drop references: while (uc->io_cnt--) vga_put(uc->pdev, VGA_RSRC_LEGACY_IO); https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/vgaarb.c?id=9b2ffa6148b1e4468d08f7e0e7e371c43cac9ffe#n1454 So this will corrupt memory. > ================================================================== > 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 > ================================================================== > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion visit https://groups.google.com/d/msgid/syzkaller-bugs/678136f7.050a0220.216c54.0015.GAE%40google.com.
