[PATCH 54/55] repair: fix segv on directory block read failure

Dave Chinner
2013-09-04T22:21:36Z

From: Dave Chinner <dchinner@redhat.com>

We try to read all blocks in the directory, but if we have a block
form directory we only have one block and so we need to fail if
there is a read error. Otherwise we try to derefence a null buffer
pointer.

While fixing the error handling for a read failure, fix the bug that
caused the read failure - trying to verify a block format buffer
with the data format buffer verifier.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
repair/phase6.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/repair/phase6.c b/repair/phase6.c
index 2a523ca..a4ad7a3 100644
--- a/repair/phase6.c
+++ b/repair/phase6.c
@@ -2064,7 +2064,7 @@ longform_dir2_entry_check(xfs_mount_t *mp,
int isleaf;
xfs_fileoff_t next_da_bno;
int seeval;
- int fixit;
+ int fixit = 0;
xfs_dir2_db_t db;

*need_dot = 1;
@@ -2091,6 +2091,8 @@ longform_dir2_entry_check(xfs_mount_t *mp,
for (da_bno = 0, next_da_bno = 0;
next_da_bno != NULLFILEOFF && da_bno < mp->m_dirleafblk;
da_bno = (xfs_dablk_t)next_da_bno) {
+ const struct xfs_buf_ops *ops;
+
next_da_bno = da_bno + mp->m_dirblkfsbs - 1;
if (bmap_next_offset(NULL, ip, &next_da_bno, XFS_DATA_FORK))
break;
@@ -2104,13 +2106,28 @@ longform_dir2_entry_check(xfs_mount_t *mp,
_("realloc failed in longform_dir2_entry_check (%zu bytes)\n"),
num_bps * sizeof(struct xfs_buf*));
}
+
+ if (isblock)
+ ops = &xfs_dir3_block_buf_ops;
+ else
+ ops = &xfs_dir3_data_buf_ops;
if (libxfs_da_read_buf(NULL, ip, da_bno, -1, &bplist[db],
- XFS_DATA_FORK, &xfs_dir3_data_buf_ops)) {
+ XFS_DATA_FORK, ops)) {
do_warn(
_("can't read data block %u for directory inode %" PRIu64 "\n"),
da_bno, ino);
*num_illegal += 1;
- continue; /* try and read all "data" blocks */
+
+ /*
+ * we try to read all "data" blocks, but if we are in
+ * block form and we fail, there isn't anything else to
+ * read, and nothing we can do but trash it.
+ */
+ if (isblock) {
+ fixit++;
+ goto out_fix;
+ }
+ continue;
}
longform_dir2_entry_check_data(mp, ip, num_illegal, need_dot,
irec, ino_offset, &bplist[db], hashtab,
@@ -2141,6 +2158,7 @@ longform_dir2_entry_check(xfs_mount_t *mp,
freetab);
}
}
+out_fix:
if (!no_modify && (fixit || dotdot_update)) {
dir_hash_dup_names(hashtab);
for (i = 0; i < freetab->naents; i++)
--
1.8.3.2