Messages in this thread | | | From | Dmitry Vyukov <> | Date | Mon, 24 Apr 2023 10:26:26 +0200 | Subject | Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2) |
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On Mon, 24 Apr 2023 at 09:58, syzbot <syzbot+702361cf7e3d95758761@syzkaller.appspotmail.com> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 457391b03803 Linux 6.3 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13226cf0280000 > kernel config: https://syzkaller.appspot.com/x/.config?x=8c81c9a3d360ebcf > dashboard link: https://syzkaller.appspot.com/bug?extid=702361cf7e3d95758761 > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/6438dcb1c42d/disk-457391b0.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/20596c249e47/vmlinux-457391b0.xz > kernel image: https://storage.googleapis.com/syzbot-assets/cb715366a3e5/bzImage-457391b0.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+702361cf7e3d95758761@syzkaller.appspotmail.com
I think shmem_mknod() needs to use i_size_write() to update the size. Writes to i_size are not assumed to be atomic throughout the kernel code.
> ================================================================== > BUG: KCSAN: data-race in generic_fillattr / shmem_mknod > > read-write to 0xffff8881049a9408 of 8 bytes by task 3383 on cpu 0: > shmem_mknod+0xdd/0x180 mm/shmem.c:2942 > shmem_create+0x34/0x40 mm/shmem.c:2994 > lookup_open fs/namei.c:3416 [inline] > open_last_lookups fs/namei.c:3484 [inline] > path_openat+0xd96/0x1d00 fs/namei.c:3712 > do_filp_open+0xf6/0x200 fs/namei.c:3742 > do_sys_openat2+0xb5/0x2a0 fs/open.c:1348 > do_sys_open fs/open.c:1364 [inline] > __do_sys_openat fs/open.c:1380 [inline] > __se_sys_openat fs/open.c:1375 [inline] > __x64_sys_openat+0xf3/0x120 fs/open.c:1375 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > read to 0xffff8881049a9408 of 8 bytes by task 4291 on cpu 1: > i_size_read include/linux/fs.h:866 [inline] > generic_fillattr+0x13f/0x1e0 fs/stat.c:58 > shmem_getattr+0x32a/0x3b0 mm/shmem.c:1068 > vfs_getattr_nosec+0x1e3/0x3c0 fs/stat.c:133 > vfs_getattr fs/stat.c:170 [inline] > vfs_statx+0x156/0x300 fs/stat.c:242 > vfs_fstatat fs/stat.c:276 [inline] > __do_sys_newfstatat fs/stat.c:446 [inline] > __se_sys_newfstatat+0x8a/0x2a0 fs/stat.c:440 > __x64_sys_newfstatat+0x55/0x60 fs/stat.c:440 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > value changed: 0x0000000000001644 -> 0x0000000000001658 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 1 PID: 4291 Comm: udevd Not tainted 6.3.0-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 > ================================================================== > > > --- > 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@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > -- > 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@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/0000000000007337c705fa1060e2%40google.com.
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