[PATCH 8/9] xfs: catch bad block numbers freeing extents.

Dave Chinner
2011-04-06T06:16:41Z

From: Dave Chinner <dchinner@redhat.com>

A fuzzed filesystem crashed a kernel when freeing an extent with a
block number beyond the end of the filesystem. Convert all the debug
asserts in xfs_free_extent() to active checks so that we catch bad
extents and return that the filesytsem is corrupted rather than
crashing.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/xfs_alloc.c | 35 ++++++++++++++++++++++++++++-------
1 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index 4bc3c64..c71e21a 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -2395,17 +2395,38 @@ xfs_free_extent(
memset(&args, 0, sizeof(xfs_alloc_arg_t));
args.tp = tp;
args.mp = tp->t_mountp;
+
+ /*
+ * validate that the block number is legal - the enables us to detect
+ * and handle a silent filesystem corruption rather than crashing.
+ */
args.agno = XFS_FSB_TO_AGNO(args.mp, bno);
- ASSERT(args.agno < args.mp->m_sb.sb_agcount);
+ if (args.agno >= args.mp->m_sb.sb_agcount)
+ return EFSCORRUPTED;
+
args.agbno = XFS_FSB_TO_AGBNO(args.mp, bno);
+ if (args.agbno >= args.mp->m_sb.sb_agblocks)
+ return EFSCORRUPTED;
+
args.pag = xfs_perag_get(args.mp, args.agno);
- if ((error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING)))
+ ASSERT(args.pag);
+
+ error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING);
+ if (error)
goto error0;
-#ifdef DEBUG
- ASSERT(args.agbp != NULL);
- ASSERT((args.agbno + len) <=
- be32_to_cpu(XFS_BUF_TO_AGF(args.agbp)->agf_length));
-#endif
+
+ /* validate the extent size is legal now we have the agf locked */
+ if (!args.agbp) {
+ error = EFSCORRUPTED;
+ goto error0;
+ }
+
+ if (args.agbno + len >
+ be32_to_cpu(XFS_BUF_TO_AGF(args.agbp)->agf_length)) {
+ error = EFSCORRUPTED;
+ goto error0;
+ }
+
error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0);
error0:
xfs_perag_put(args.pag);
--
1.7.2.3