Re: [PATCH 3/3] fs/btrfs: avoid null pointer dereference if reloc control has not been initialized

[David Sterba]

On Sun, Dec 27, 2020 at 10:55:31PM +0800, Defang Bo wrote:
> Similar to commmit<389305b2>,

Please use full commit reference like 389305b2aa68 ("btrfs: relocation:
Only remove reloc rb_trees if reloc control has been initialized")

> it turns out that fs_info::reloc_ctl can be NULL ,

Please describe how the NULL can get there.

[PATCH 3/3] fs/btrfs: avoid null pointer dereference if reloc control has not been initialized

[Defang Bo]

Similar to commmit<389305b2>, it turns out that fs_info::reloc_ctl can be NULL ,
so there should be a check for rc to prevent null pointer dereference.

Signed-off-by: Defang Bo 
---
 fs/btrfs/relocation.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 3602806..ca03571 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -626,6 +626,9 @@ static int __must_check __add_reloc_root(struct btrfs_root 
*root)
struct mapping_node *node;
struct reloc_control *rc = fs_info->reloc_ctl;
 
+   if (!rc)
+   return 0;
+
node = kmalloc(sizeof(*node), GFP_NOFS);
if (!node)
return -ENOMEM;
@@ -703,6 +706,9 @@ static int __update_reloc_root(struct btrfs_root *root)
struct rb_node *rb_node;
struct mapping_node *node = NULL;
struct reloc_control *rc = fs_info->reloc_ctl;
+
+   if (!rc)
+   return 0;
 
spin_lock(>reloc_root_tree.lock);
rb_node = rb_simple_search(>reloc_root_tree.rb_root,
-- 
2.7.4