Messages in this thread | | | From | harshad shirwadkar <> | Date | Mon, 5 Apr 2021 09:26:14 -0700 | Subject | Re: KCSAN: data-race in ext4_fc_commit / ext4_fc_commit |
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Thanks for the report Hao! I think following lines in fast_commit.c are the culprit:
if (likely(sbi->s_fc_avg_commit_time)) sbi->s_fc_avg_commit_time = (commit_time + sbi->s_fc_avg_commit_time * 3) / 4; else sbi->s_fc_avg_commit_time = commit_time;
This should have been done after taking sbi level lock, but this is happening after releasing the lock.
I'll send a patch to fix this, thanks again!
- Harshad
On Sun, Apr 4, 2021 at 2:52 AM Hao Sun <sunhao.th@gmail.com> wrote: > > Hi: > > When using Healer(https://github.com/SunHao-0/healer/tree/dev) to fuzz > the Linux kernel, I found a data-race vulnerability in ext4_fc_commit > / ext4_fc_commit, which looks strange. > Sorry, data-race is usually difficult to reproduce. I cannot provide > you with a reproducing program. > I hope that the call stack information in the crash log can help you > locate the problem. > Kernel config and full log can be found in the attachment. > > Here is the detailed information: > commit: 3b9cdafb5358eb9f3790de2f728f765fef100731 > version: linux 5.11 > git tree: upstream > report: > ================================================================== > BUG: KCSAN: data-race in ext4_fc_commit / ext4_fc_commit > write to 0xffff88800dd89f10 of 8 bytes by task 12063 on cpu 0: > ext4_fc_commit+0x1e6/0x1850 linux/fs/ext4/fast_commit.c:1205 > ext4_fsync_journal linux/fs/ext4/fsync.c:115 [inline] > ext4_sync_file+0x38c/0x6d0 linux/fs/ext4/fsync.c:174 > vfs_fsync_range linux/fs/sync.c:200 [inline] > vfs_fsync linux/fs/sync.c:214 [inline] > do_fsync linux/fs/sync.c:224 [inline] > __do_sys_fdatasync linux/fs/sync.c:237 [inline] > __se_sys_fdatasync linux/fs/sync.c:235 [inline] > __x64_sys_fdatasync+0x7a/0xd0 linux/fs/sync.c:235 > do_syscall_64+0x39/0x80 linux/arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xae
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