commit e5880d76aea443b04e07da19830da0f6f7494eef
author Theodore Ts'o <tytso@mit.edu> Tue Jul 27 11:56:04 2010 -0400
committer Theodore Ts'o <tytso@mit.edu> Tue Jul 27 11:56:04 2010 -0400
tree 24ad55c300a63170ffcf5a777dc737c67d80e00c
parent 89eeddf03327e19cfcbb18efa98e5470e2f5c563

ext4: fix potential NULL dereference while tracing

The allocation_context pointer can be NULL.

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

fs/ext4/mballoc.c

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3dfad95..8b3b934 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3575,7 +3575,7 @@
 			trace_ext4_mballoc_discard(ac);
 		}
 
-		trace_ext4_mb_release_inode_pa(ac, pa, grp_blk_start + bit,
+		trace_ext4_mb_release_inode_pa(sb, ac, pa, grp_blk_start + bit,
 					       next - bit);
 		mb_free_blocks(pa->pa_inode, e4b, bit, next - bit);
 		bit = next + 1;
@@ -3606,7 +3606,7 @@
 	ext4_group_t group;
 	ext4_grpblk_t bit;
 
-	trace_ext4_mb_release_group_pa(ac, pa);
+	trace_ext4_mb_release_group_pa(sb, ac, pa);
 	BUG_ON(pa->pa_deleted == 0);
 	ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
 	BUG_ON(group != e4b->bd_group && pa->pa_len != 0);

include/trace/events/ext4.h

diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index f3865c7..01e9e00 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -395,11 +395,12 @@
 );
 
 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 @@
 	),
 
 	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_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 @@
 	),
 
 	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;
 	),