Commit 4e3c51f4 authored by Svyatoslav Feldsherov's avatar Svyatoslav Feldsherov Committed by Theodore Ts'o
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fs: do not update freeing inode i_io_list 



After commit cbfecb92 ("fs: record I_DIRTY_TIME even if inode
already has I_DIRTY_INODE") writeback_single_inode can push inode with
I_DIRTY_TIME set to b_dirty_time list. In case of freeing inode with
I_DIRTY_TIME set this can happen after deletion of inode from i_io_list
at 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->i_io_list. Add explicit check to avoid it.

Fixes: cbfecb92 ("fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE")
Reported-by: default avatar <syzbot+6ba92bd00d5093f7e371@syzkaller.appspotmail.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarSvyatoslav Feldsherov <feldsherov@google.com>
Link: https://lore.kernel.org/r/20221115202001.324188-1-feldsherov@google.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent f6b1a1cf

fs/fs-writeback.c

+19 −11
Original line number Diff line number Diff line
@@ -1712,9 +1712,14 @@ 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, its i_io_list shoudn't be updated

	 * as it can be finally deleted at this moment.

	 */

	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);
@@ -1723,7 +1728,10 @@ static int writeback_single_inode(struct inode *inode, 
				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);

				inode_io_list_move_locked(inode,

							  wb,

							  &wb->b_dirty_time);

			}

		}

	}