Hi All, I guess this can be fixed by READ_ONCE(disk->diskseq) while reading and WRITE_ONCE(disk->diskseq, atomic64_inc_return(&diskseq)) in inc_diskseq() to avoid data race. I can probably send a patch if my understanding is correct. Best Regards, Santosh On Wed, Jun 19, 2024 at 5:57 PM syzbot <syzbot+c147f9175ec6cc7bd73b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 3d54351c64e8 Merge tag 'lsm-pr-20240617' of git://git.kern.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=12426cfa980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=cd45aedbb3f7637b > dashboard link: https://syzkaller.appspot.com/bug?extid=c147f9175ec6cc7bd73b > 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/ba0a777cccff/disk-3d54351c.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/a78193318c92/vmlinux-3d54351c.xz > kernel image: https://storage.googleapis.com/syzbot-assets/54456f3d3bfe/bzImage-3d54351c.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+c147f9175ec6cc7bd73b@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KCSAN: data-race in block_uevent / inc_diskseq > > write to 0xffff888101f05220 of 8 bytes by task 3101 on cpu 0: > inc_diskseq+0x2c/0x40 block/genhd.c:1472 > disk_force_media_change+0x9f/0xf0 block/disk-events.c:297 > __loop_clr_fd+0x270/0x3f0 drivers/block/loop.c:1193 > loop_clr_fd drivers/block/loop.c:1276 [inline] > lo_ioctl+0xea6/0x1330 drivers/block/loop.c:1578 > blkdev_ioctl+0x35f/0x450 block/ioctl.c:676 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:907 [inline] > __se_sys_ioctl+0xd3/0x150 fs/ioctl.c:893 > __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893 > x64_sys_call+0x1581/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:17 > 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 to 0xffff888101f05220 of 8 bytes by task 3091 on cpu 1: > block_uevent+0x31/0x50 block/genhd.c:1206 > dev_uevent+0x2f3/0x380 drivers/base/core.c:2687 > uevent_show+0x11e/0x210 drivers/base/core.c:2745 > dev_attr_show+0x3a/0xa0 drivers/base/core.c:2437 > sysfs_kf_seq_show+0x17c/0x250 fs/sysfs/file.c:59 > kernfs_seq_show+0x7c/0x90 fs/kernfs/file.c:205 > seq_read_iter+0x2d7/0x940 fs/seq_file.c:230 > kernfs_fop_read_iter+0xc6/0x310 fs/kernfs/file.c:279 > new_sync_read fs/read_write.c:395 [inline] > vfs_read+0x5e6/0x6e0 fs/read_write.c:476 > ksys_read+0xeb/0x1b0 fs/read_write.c:619 > __do_sys_read fs/read_write.c:629 [inline] > __se_sys_read fs/read_write.c:627 [inline] > __x64_sys_read+0x42/0x50 fs/read_write.c:627 > x64_sys_call+0x27e5/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:1 > 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: 0x0000000000000045 -> 0x0000000000000048 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 3091 Comm: udevd Not tainted 6.10.0-rc4-syzkaller-00035-g3d54351c64e8 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024 > ================================================================== > > > --- > 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 >
