[PATCH 4.10 16/81] xfs: correct null checks and error processing in xfs_initialize_perag

Greg Kroah-Hartman
2017-04-06T09:11:49Z

From: Bill O'Donnell <billodo@redhat.com>

commit b20fe4730ea5c037c16631fb0df659c7b6d4b3b1 upstream.

If pag cannot be allocated, the current error exit path will trip
a null pointer deference error when calling xfs_buf_hash_destroy
with a null pag. Fix this by adding a new error exit labels and
jumping to those accordingly, avoiding the hash destroy and
unnecessary kmem_free on pag.

Up to three things need to be properly unwound:

1) pag memory allocation
2) xfs_buf_hash_init
3) radix_tree_insert

For any given iteration through the loop, any of the above which
succeed must be unwound for /this/ pag, and then all prior
initialized pags must be unwound.

Addresses-Coverity-Id: 1397628 ("Dereference after null check")

Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/xfs/xfs_mount.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -187,7 +187,7 @@ xfs_initialize_perag(
xfs_agnumber_t *maxagi)
{
xfs_agnumber_t index;
- xfs_agnumber_t first_initialised = 0;
+ xfs_agnumber_t first_initialised = NULLAGNUMBER;
xfs_perag_t *pag;
int error = -ENOMEM;

@@ -202,22 +202,20 @@ xfs_initialize_perag(
xfs_perag_put(pag);
continue;
}
- if (!first_initialised)
- first_initialised = index;

pag = kmem_zalloc(sizeof(*pag), KM_MAYFAIL);
if (!pag)
- goto out_unwind;
+ goto out_unwind_new_pags;
pag->pag_agno = index;
pag->pag_mount = mp;
spin_lock_init(&pag->pag_ici_lock);
mutex_init(&pag->pag_ici_reclaim_lock);
INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
if (xfs_buf_hash_init(pag))
- goto out_unwind;
+ goto out_free_pag;

if (radix_tree_preload(GFP_NOFS))
- goto out_unwind;
+ goto out_hash_destroy;

spin_lock(&mp->m_perag_lock);
if (radix_tree_insert(&mp->m_perag_tree, index, pag)) {
@@ -225,10 +223,13 @@ xfs_initialize_perag(
spin_unlock(&mp->m_perag_lock);
radix_tree_preload_end();
error = -EEXIST;
- goto out_unwind;
+ goto out_hash_destroy;
}
spin_unlock(&mp->m_perag_lock);
radix_tree_preload_end();
+ /* first new pag is fully initialized */
+ if (first_initialised == NULLAGNUMBER)
+ first_initialised = index;
}

index = xfs_set_inode_alloc(mp, agcount);
@@ -239,11 +240,16 @@ xfs_initialize_perag(
mp->m_ag_prealloc_blocks = xfs_prealloc_blocks(mp);
return 0;

-out_unwind:
+out_hash_destroy:
xfs_buf_hash_destroy(pag);
+out_free_pag:
kmem_free(pag);
- for (; index > first_initialised; index--) {
+out_unwind_new_pags:
+ /* unwind any prior newly initialized pags */
+ for (index = first_initialised; index < agcount; index++) {
pag = radix_tree_delete(&mp->m_perag_tree, index);
+ if (!pag)
+ break;
xfs_buf_hash_destroy(pag);
kmem_free(pag);
}