ext4: fix potential NULL dereference while tracing

The allocation_context pointer can be NULL.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 12 insertions, 8 deletions

diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index f3865c7b4166..01e9e0076a92 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -395,11 +395,12 @@ DEFINE_EVENT(ext4__mb_new_pa, ext4_mb_new_group_pa,
 );
 
 TRACE_EVENT(ext4_mb_release_inode_pa,
-        TP_PROTO(struct ext4_allocation_context *ac,
+        TP_PROTO(struct super_block *sb,
+                 struct ext4_allocation_context *ac,
                  struct ext4_prealloc_space *pa,
                  unsigned long long block, unsigned int count),
 
-        TP_ARGS(ac, pa, block, count),
+        TP_ARGS(sb, ac, pa, block, count),
 
         TP_STRUCT__entry(
                 __field(        dev_t,  dev                     )
@@ -410,8 +411,9 @@ TRACE_EVENT(ext4_mb_release_inode_pa,
         ),
 
         TP_fast_assign(
-                __entry->dev            = ac->ac_sb->s_dev;
-                __entry->ino            = ac->ac_inode->i_ino;
+                __entry->dev            = sb->s_dev;
+                __entry->ino            = (ac && ac->ac_inode) ? 
+                                                ac->ac_inode->i_ino : 0;
                 __entry->block          = block;
                 __entry->count          = count;
         ),
@@ -422,10 +424,11 @@ TRACE_EVENT(ext4_mb_release_inode_pa,
 );
 
 TRACE_EVENT(ext4_mb_release_group_pa,
-        TP_PROTO(struct ext4_allocation_context *ac,
+        TP_PROTO(struct super_block *sb,
+                 struct ext4_allocation_context *ac,
                  struct ext4_prealloc_space *pa),
 
-        TP_ARGS(ac, pa),
+        TP_ARGS(sb, ac, pa),
 
         TP_STRUCT__entry(
                 __field(        dev_t,  dev                     )
@@ -436,8 +439,9 @@ TRACE_EVENT(ext4_mb_release_group_pa,
         ),
 
         TP_fast_assign(
-                __entry->dev            = ac->ac_sb->s_dev;
-                __entry->ino            = ac->ac_inode->i_ino;
+                __entry->dev            = sb->s_dev;
+                __entry->ino            = (ac && ac->ac_inode) ?
+                                                ac->ac_inode->i_ino : 0;
                 __entry->pa_pstart      = pa->pa_pstart;
                 __entry->pa_len         = pa->pa_len;
         ),