Re: [patch v2 1/2] Btrfs: fix possible memory leak in find_parent_nodes()

[Jan Schmidt]

 
On Fri, August 09, 2013 at 07:25 (+0200), Wang Shilong wrote:
 The origin code dealt with 'ref' as following steps:
   |-list_del(ref-list)
   |-some operations
   |-kfree(ref)
 
 If operations failed, it would goto label 'out' without freeing this 'ref'.
 and then memory leak would happen.Just move list_del() after kfree()
 will fix the problem.

Still not sufficient as an explanation. What is missing is the hint that in the
error handling code, we free everything that's left in the prefs list.

-Jan

 Signed-off-by: Wang Shilong wangsl.f...@cn.fujitsu.com
 Reviewed-by: Miao Xie mi...@cn.fujitsu.com
 ---
 V1-V2: add explanations to changelog
 ---
  fs/btrfs/backref.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
 index 68048d6..7b55c95 100644
 --- a/fs/btrfs/backref.c
 +++ b/fs/btrfs/backref.c
 @@ -911,7 +911,6 @@ again:
  
   while (!list_empty(prefs)) {
   ref = list_first_entry(prefs, struct __prelim_ref, list);
 - list_del(ref-list);
   WARN_ON(ref-count  0);
   if (ref-count  ref-root_id  ref-parent == 0) {
   /* no parent == root of tree */
 @@ -956,6 +955,7 @@ again:
   eie-next = ref-inode_list;
   }
   }
 + list_del(ref-list);
   kfree(ref);
   }
  
 
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[patch v2 1/2] Btrfs: fix possible memory leak in find_parent_nodes()

[Wang Shilong]

The origin code dealt with 'ref' as following steps:
|-list_del(ref-list)
|-some operations
|-kfree(ref)

If operations failed, it would goto label 'out' without freeing this 'ref'.
and then memory leak would happen.Just move list_del() after kfree()
will fix the problem.

Signed-off-by: Wang Shilong wangsl.f...@cn.fujitsu.com
Reviewed-by: Miao Xie mi...@cn.fujitsu.com
---
V1-V2: add explanations to changelog
---
 fs/btrfs/backref.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 68048d6..7b55c95 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -911,7 +911,6 @@ again:
 
while (!list_empty(prefs)) {
ref = list_first_entry(prefs, struct __prelim_ref, list);
-   list_del(ref-list);
WARN_ON(ref-count  0);
if (ref-count  ref-root_id  ref-parent == 0) {
/* no parent == root of tree */
@@ -956,6 +955,7 @@ again:
eie-next = ref-inode_list;
}
}
+   list_del(ref-list);
kfree(ref);
}
 
-- 
1.8.0.1

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