This is a note to let you know that I've just added the patch titled
xfs: avoid mount-time deadlock in CoW extent recovery
to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfs-avoid-mount-time-deadlock-in-cow-extent-recovery.patch
and it can be found in the queue-4.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3ecb3ac7b950ff8f6c6a61e8b7b0d6e3546429a0 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Date: Mon, 15 May 2017 19:16:15 -0700
Subject: xfs: avoid mount-time deadlock in CoW extent recovery
From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
commit 3ecb3ac7b950ff8f6c6a61e8b7b0d6e3546429a0 upstream.
If a malicious user corrupts the refcount btree to cause a cycle between
different levels of the tree, the next mount attempt will deadlock in
the CoW recovery routine while grabbing buffer locks. We can use the
ability to re-grab a buffer that was previous locked to a transaction to
avoid deadlocks, so do that here.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/xfs/libxfs/xfs_refcount.c | 43 +++++++++++++++++++++++++++++++------------
1 file changed, 31 insertions(+), 12 deletions(-)
--- a/fs/xfs/libxfs/xfs_refcount.c
+++ b/fs/xfs/libxfs/xfs_refcount.c
@@ -1629,13 +1629,28 @@ xfs_refcount_recover_cow_leftovers(
if (mp->m_sb.sb_agblocks >= XFS_REFC_COW_START)
return -EOPNOTSUPP;
- error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
+ INIT_LIST_HEAD(&debris);
+
+ /*
+ * In this first part, we use an empty transaction to gather up
+ * all the leftover CoW extents so that we can subsequently
+ * delete them. The empty transaction is used to avoid
+ * a buffer lock deadlock if there happens to be a loop in the
+ * refcountbt because we're allowed to re-grab a buffer that is
+ * already attached to our transaction. When we're done
+ * recording the CoW debris we cancel the (empty) transaction
+ * and everything goes away cleanly.
+ */
+ error = xfs_trans_alloc_empty(mp, &tp);
if (error)
return error;
- cur = xfs_refcountbt_init_cursor(mp, NULL, agbp, agno, NULL);
+
+ error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
+ if (error)
+ goto out_trans;
+ cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, NULL);
/* Find all the leftover CoW staging extents. */
- INIT_LIST_HEAD(&debris);
memset(&low, 0, sizeof(low));
memset(&high, 0, sizeof(high));
low.rc.rc_startblock = XFS_REFC_COW_START;
@@ -1645,10 +1660,11 @@ xfs_refcount_recover_cow_leftovers(
if (error)
goto out_cursor;
xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
- xfs_buf_relse(agbp);
+ xfs_trans_brelse(tp, agbp);
+ xfs_trans_cancel(tp);
/* Now iterate the list to free the leftovers */
- list_for_each_entry(rr, &debris, rr_list) {
+ list_for_each_entry_safe(rr, n, &debris, rr_list) {
/* Set up transaction. */
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0, 0, &tp);
if (error)
@@ -1676,8 +1692,16 @@ xfs_refcount_recover_cow_leftovers(
error = xfs_trans_commit(tp);
if (error)
goto out_free;
+
+ list_del(&rr->rr_list);
+ kmem_free(rr);
}
+ return error;
+out_defer:
+ xfs_defer_cancel(&dfops);
+out_trans:
+ xfs_trans_cancel(tp);
out_free:
/* Free the leftover list */
list_for_each_entry_safe(rr, n, &debris, rr_list) {
@@ -1688,11 +1712,6 @@ out_free:
out_cursor:
xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
- xfs_buf_relse(agbp);
- goto out_free;
-
-out_defer:
- xfs_defer_cancel(&dfops);
- xfs_trans_cancel(tp);
- goto out_free;
+ xfs_trans_brelse(tp, agbp);
+ goto out_trans;
}
Patches currently in stable-queue which might be from darrick.wong@xxxxxxxxxx are
queue-4.11/xfs-fix-missed-holes-in-seek_hole-implementation.patch
queue-4.11/xfs-fix-indlen-accounting-error-on-partial-delalloc-conversion.patch
queue-4.11/xfs-fix-over-copying-of-getbmap-parameters-from-userspace.patch
queue-4.11/xfs-bad-assertion-for-delalloc-an-extent-that-start-at-i_size.patch
queue-4.11/xfs-bmapx-shouldn-t-barf-on-inline-format-directories.patch
queue-4.11/xfs-drop-iolock-from-reclaim-context-to-appease-lockdep.patch
queue-4.11/mm-avoid-spurious-bad-pmd-warning-messages.patch
queue-4.11/xfs-fix-off-by-one-on-max-nr_pages-in-xfs_find_get_desired_pgoff.patch
queue-4.11/xfs-update-ag-iterator-to-support-wait-on-new-inodes.patch
queue-4.11/xfs-use-dedicated-log-worker-wq-to-avoid-deadlock-with-cil-wq.patch
queue-4.11/xfs-fix-up-quotacheck-buffer-list-error-handling.patch
queue-4.11/xfs-wait-on-new-inodes-during-quotaoff-dquot-release.patch
queue-4.11/dax-fix-race-between-colliding-pmd-pte-entries.patch
queue-4.11/xfs-use-b_state-to-fix-buffer-i-o-accounting-release-race.patch
queue-4.11/xfs-avoid-mount-time-deadlock-in-cow-extent-recovery.patch
queue-4.11/xfs-fix-off-by-in-in-loop-termination-in-xfs_find_get_desired_pgoff.patch
queue-4.11/xfs-xfs_trans_alloc_empty.patch
queue-4.11/xfs-fix-integer-truncation-in-xfs_bmap_remap_alloc.patch
queue-4.11/xfs-actually-report-xattr-extents-via-iomap.patch
queue-4.11/xfs-fix-use-after-free-in-xfs_finish_page_writeback.patch
queue-4.11/xfs-reserve-enough-blocks-to-handle-btree-splits-when-remapping.patch
queue-4.11/xfs-support-ability-to-wait-on-new-inodes.patch
queue-4.11/xfs-prevent-multi-fsb-dir-readahead-from-reading-random-blocks.patch
queue-4.11/xfs-fix-unaligned-access-in-xfs_btree_visit_blocks.patch
queue-4.11/xfs-handle-array-index-overrun-in-xfs_dir2_leaf_readbuf.patch