Re: [PATCH] ocfs2: reject inconsistent inode size before truncate

[ZhengYuan Huang]

On Sun, May 10, 2026 at 11:54 AM Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> wrote:
>
>
>
> On 5/9/26 5:10 PM, ZhengYuan Huang wrote:
> > [BUG]
> > openat(..., O_WRONLY|O_CREAT|O_TRUNC) can hit:
> >
> > kernel BUG at fs/ocfs2/file.c:454!
> > Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
> > RIP: 0010:ocfs2_truncate_file+0x1204/0x13c0 fs/ocfs2/file.c:454
> > Call Trace:
> >  ocfs2_setattr+0xa6d/0x1fd0 fs/ocfs2/file.c:1212
> >  notify_change+0x4b5/0x1030 fs/attr.c:546
> >  do_truncate+0x1d2/0x230 fs/open.c:68
> >  handle_truncate fs/namei.c:3596 [inline]
> >  do_open fs/namei.c:3979 [inline]
> >  path_openat+0x260f/0x2ce0 fs/namei.c:4134
> >  do_filp_open+0x1f6/0x430 fs/namei.c:4161
> >  do_sys_openat2+0x117/0x1c0 fs/open.c:1437
> >  do_sys_open fs/open.c:1452 [inline]
> >  __do_sys_openat fs/open.c:1468 [inline]
> >  __se_sys_openat fs/open.c:1463 [inline]
> >  __x64_sys_openat+0x15b/0x220 fs/open.c:1463
> >  ...
> >
> > [CAUSE]
> > ocfs2_truncate_file() treats di_bh->i_size matching inode->i_size as an
> > internal code invariant and BUGs if it is broken.
> >
> > That assumption is too strong for corrupted metadata. The dinode block can
> > still be structurally valid enough to pass ocfs2_read_inode_block() while
> > no longer matching an already-instantiated VFS inode. On local mounts,
> > ocfs2_inode_lock_update() skips refresh entirely, so truncate can
> > observe the mismatch directly and crash instead of rejecting the
> > corruption.
> >
> > [FIX]
> > Turn the BUG_ON into normal OCFS2 corruption handling. If truncate sees
> > di_bh->i_size disagree with inode->i_size, report it with ocfs2_error() and
> > abort before touching truncate state.
> >
> > This keeps the fix at the first boundary that actually requires the
> > sizes to match and avoids widening checks into hotter generic
> > inode-lock paths.
> >
> > Signed-off-by: ZhengYuan Huang <gality369@xxxxxxxxx>
> > ---
> > diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> > --- a/fs/ocfs2/file.c
> > +++ b/fs/ocfs2/file.c
> > @@ -444,15 +444,17 @@ int ocfs2_truncate_file(struct inode *inode,
> >       int status = 0;
> >       struct ocfs2_dinode *fe = NULL;
> >       struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> >
> > -     /* We trust di_bh because it comes from ocfs2_inode_lock(), which
> > -      * already validated it */
> > +     /*
> > +      * ocfs2_inode_lock() validated the dinode block, but truncation
> > +      * still needs to reject an inode state that no longer matches
> > +      * di_bh.
> > +      */
>
> In commit log, you mention the case is local mount.
> So here comments should refer it.
>
> Thanks,
> Joseph
>
> >       fe = (struct ocfs2_dinode *) di_bh->b_data;
> >
> >       trace_ocfs2_truncate_file((unsigned long long)OCFS2_I(inode)->ip_blkno,
> >                                 (unsigned long long)le64_to_cpu(fe->i_size),
> >                                 (unsigned long long)new_i_size);
> >
> > -     mlog_bug_on_msg(le64_to_cpu(fe->i_size) != i_size_read(inode),
> > -                     "Inode %llu, inode i_size = %lld != di "
> > -                     "i_size = %llu, i_flags = 0x%x\n",
> > -                     (unsigned long long)OCFS2_I(inode)->ip_blkno,
> > -                     i_size_read(inode),
> > -                     (unsigned long long)le64_to_cpu(fe->i_size),
> > -                     le32_to_cpu(fe->i_flags));
> > +     if (unlikely(le64_to_cpu(fe->i_size) != i_size_read(inode))) {
> > +             status = ocfs2_error(inode->i_sb,
> > +                                  "Inode %llu has inconsistent i_size: inode = %lld, dinode = %llu, i_flags = 0x%x\n",
> > +                                  (unsigned long long)OCFS2_I(inode)->ip_blkno,
> > +                                  i_size_read(inode),
> > +                                  (unsigned long long)le64_to_cpu(fe->i_size),
> > +                                  le32_to_cpu(fe->i_flags));
> > +             goto bail;
> > +     }
> >
> >       if (new_i_size > le64_to_cpu(fe->i_size)) {
> >               trace_ocfs2_truncate_file_error(
> >                       (unsigned long long)le64_to_cpu(fe->i_size),
>

Thanks for the review.

That makes sense. I have updated the comment to mention the local mount
case explicitly and sent a v2 patch.

Thanks,
ZhengYuan Huang