This problem happened locally with a bad inode number from xfs
recovery. xfs_perag_get() can return NULL if given a bad agno.
Most callers of xfs_perag_get() do not check for a NULL before
using the pointer. This patch forces a shutdown of the filesystem
for those callers that do not check the return value rather than
crashing on a dereferenced NULL pointer.
Signed-off-by: Mark Tinguely <tinguely@xxxxxxx>
---
fs/xfs/xfs_icache.c | 2 +-
fs/xfs/xfs_mount.c | 4 ++--
fs/xfs/xfs_mount.h | 17 ++++++++++++++++-
3 files changed, 19 insertions(+), 4 deletions(-)
Index: b/fs/xfs/xfs_icache.c
===================================================================
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -656,7 +656,7 @@ xfs_inode_ag_iterator(
xfs_agnumber_t ag;
ag = 0;
- while ((pag = xfs_perag_get(mp, ag))) {
+ while ((pag = __xfs_perag_get(mp, ag))) {
ag = pag->pag_agno + 1;
error = xfs_inode_ag_walk(mp, pag, execute, flags, args, -1);
xfs_perag_put(pag);
Index: b/fs/xfs/xfs_mount.c
===================================================================
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -193,7 +193,7 @@ xfs_uuid_unmount(
* have to protect against changes is the tree structure itself.
*/
struct xfs_perag *
-xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
+__xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
{
struct xfs_perag *pag;
int ref = 0;
@@ -442,7 +442,7 @@ xfs_initialize_perag(
* AGs we don't find ready for initialisation.
*/
for (index = 0; index < agcount; index++) {
- pag = xfs_perag_get(mp, index);
+ pag = __xfs_perag_get(mp, index);
if (pag) {
xfs_perag_put(pag);
continue;
Index: b/fs/xfs/xfs_mount.h
===================================================================
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -336,12 +336,27 @@ xfs_daddr_to_agbno(struct xfs_mount *mp,
/*
* perag get/put wrappers for ref counting
*/
-struct xfs_perag *xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno);
+struct xfs_perag *__xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno);
struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *mp, xfs_agnumber_t agno,
int tag);
void xfs_perag_put(struct xfs_perag *pag);
/*
+ * Ensure the per AG entry was found. Shutting down the filesystem
+ * is better than crashing the OS.
+ */
+static inline struct xfs_perag *
+xfs_perag_get(struct xfs_mount *mp, xfs_agnumber_t agno)
+{
+ struct xfs_perag *pag;
+
+ pag = __xfs_perag_get(mp, agno);
+ if (!pag)
+ xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+ return pag;
+}
+
+/*
* Per-cpu superblock locking functions
*/
#ifdef HAVE_PERCPU_SB
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