Thank you for the review.
I've sent v3 with proposed fixes.
Also tried to be more consistent and use i_io_list in comments and
commit message instead of io_list//io list.
On Tue, Nov 15, 2022 at 12:55 PM Jan Kara <jack@xxxxxxx> wrote:
>
> On Mon 14-11-22 21:21:55, Svyatoslav Feldsherov wrote:
> > After commit cbfecb927f42 ("fs: record I_DIRTY_TIME even if inode
> > already has I_DIRTY_INODE") writeiback_single_inode can push inode with
> ^^^ writeback
>
> > I_DIRTY_TIME set to b_dirty_time list. In case of freeing inode with
> > I_DIRTY_TIME set this can happened after deletion of inode io_list at
> ^^ happen ^^^ deletion of
> inode *from i_io_list*
>
> > evict. Stack trace is following.
> >
> > evict
> > fat_evict_inode
> > fat_truncate_blocks
> > fat_flush_inodes
> > writeback_inode
> > sync_inode_metadata(inode, sync=0)
> > writeback_single_inode(inode, wbc) <- wbc->sync_mode == WB_SYNC_NONE
> >
> > This will lead to use after free in flusher thread.
> >
> > Similar issue can be triggered if writeback_single_inode in the
> > stack trace update inode->io_list. Add explicit check to avoid it.
> ^^ inode->i_io_list
>
> > Fixes: cbfecb927f42 ("fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE")
> > Reported-by: syzbot+6ba92bd00d5093f7e371@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Svyatoslav Feldsherov <feldsherov@xxxxxxxxxx>
>
> Besides these gramatical nits the patch looks good to me. Feel free to add:
>
> Reviewed-by: Jan Kara <jack@xxxxxxx>
>
> Thanks!
>
> Honza
>
> > ---
> > V1 -> V2:
> > - address review comments
> > - skip inode_cgwb_move_to_attached for freeing inode
> >
> > fs/fs-writeback.c | 30 +++++++++++++++++++-----------
> > 1 file changed, 19 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> > index 443f83382b9b..c4aea096689c 100644
> > --- a/fs/fs-writeback.c
> > +++ b/fs/fs-writeback.c
> > @@ -1712,18 +1712,26 @@ static int writeback_single_inode(struct inode *inode,
> > wb = inode_to_wb_and_lock_list(inode);
> > spin_lock(&inode->i_lock);
> > /*
> > - * If the inode is now fully clean, then it can be safely removed from
> > - * its writeback list (if any). Otherwise the flusher threads are
> > - * responsible for the writeback lists.
> > + * If the inode is freeing, it's io_list shoudn't be updated
> > + * as it can be finally deleted at this moment.
> > */
> > - if (!(inode->i_state & I_DIRTY_ALL))
> > - inode_cgwb_move_to_attached(inode, wb);
> > - else if (!(inode->i_state & I_SYNC_QUEUED)) {
> > - if ((inode->i_state & I_DIRTY))
> > - redirty_tail_locked(inode, wb);
> > - else if (inode->i_state & I_DIRTY_TIME) {
> > - inode->dirtied_when = jiffies;
> > - inode_io_list_move_locked(inode, wb, &wb->b_dirty_time);
> > + if (!(inode->i_state & I_FREEING)) {
> > + /*
> > + * If the inode is now fully clean, then it can be safely
> > + * removed from its writeback list (if any). Otherwise the
> > + * flusher threads are responsible for the writeback lists.
> > + */
> > + if (!(inode->i_state & I_DIRTY_ALL))
> > + inode_cgwb_move_to_attached(inode, wb);
> > + else if (!(inode->i_state & I_SYNC_QUEUED)) {
> > + if ((inode->i_state & I_DIRTY))
> > + redirty_tail_locked(inode, wb);
> > + else if (inode->i_state & I_DIRTY_TIME) {
> > + inode->dirtied_when = jiffies;
> > + inode_io_list_move_locked(inode,
> > + wb,
> > + &wb->b_dirty_time);
> > + }
> > }
> > }
> >
> > --
> > 2.38.1.431.g37b22c650d-goog
> >
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
--
Slava
