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

To: xfs@xxxxxxxxxxx
Subject: [PATCH 54/55] repair: fix segv on directory block read failure
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 5 Sep 2013 08:05:58 +1000
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1378332359-14737-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1378332359-14737-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 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

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