linux-kernel - [PATCH 4.9 46/48] xfs: handle error if xfs_btree_get

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Date:   Tue, 24 Oct 2017 15:03:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jason L Tibbitts III <tibbs@...h.uh.edu>,
        Eric Sandeen <sandeen@...hat.com>,
        Christoph Hellwig <hch@....de>,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: [PATCH 4.9 46/48] xfs: handle error if xfs_btree_get_bufs fails

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@...deen.net>

commit 93e8befc17f6d6ea92b0aee3741ceac8bca4590f upstream.

Jason reported that a corrupted filesystem failed to replay
the log with a metadata block out of bounds warning:

XFS (dm-2): _xfs_buf_find: Block out of range: block 0x80270fff8, EOFS 0x9c40000

_xfs_buf_find() and xfs_btree_get_bufs() return NULL if
that happens, and then when xfs_alloc_fix_freelist() calls
xfs_trans_binval() on that NULL bp, we oops with:

BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8

We don't handle _xfs_buf_find errors very well, every
caller higher up the stack gets to guess at why it failed.
But we should at least handle it somehow, so return
EFSCORRUPTED here.

Reported-by: Jason L Tibbitts III <tibbs@...h.uh.edu>
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/xfs/libxfs/xfs_alloc.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -1579,6 +1579,10 @@ xfs_alloc_ag_vextent_small(

 				bp = xfs_btree_get_bufs(args->mp, args->tp,
 					args->agno, fbno, 0);
+				if (!bp) {
+					error = -EFSCORRUPTED;
+					goto error0;
+				}
 				xfs_trans_binval(args->tp, bp);
 			}
 			args->len = 1;
@@ -2136,6 +2140,10 @@ xfs_alloc_fix_freelist(
 		if (error)
 			goto out_agbp_relse;
 		bp = xfs_btree_get_bufs(mp, tp, args->agno, bno, 0);
+		if (!bp) {
+			error = -EFSCORRUPTED;
+			goto out_agbp_relse;
+		}
 		xfs_trans_binval(tp, bp);
 	}