[PATCH] btrfs: Fix incorrect check causing NULL pointer derefernce

[PATCH] btrfs: Fix incorrect check causing NULL pointer derefernce

[Aditya Pakki]

In btrfsic_process_superblock, argument state is dereferenced for
the variable fs_info and then checked for NULL. The patch fixes
this issue by returning an error if state is NULL and then assigns
fs_info.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
---
 fs/btrfs/check-integrity.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 0b52ab4cb964..70d7a05cafad 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -629,15 +629,18 @@ static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
 static int btrfsic_process_superblock(struct btrfsic_state *state,
 				      struct btrfs_fs_devices *fs_devices)
 {
-	struct btrfs_fs_info *fs_info = state->fs_info;
-	struct btrfs_super_block *selected_super;
+	struct btrfsic_dev_state *selected_dev_state = NULL;
 	struct list_head *dev_head = &fs_devices->devices;
+	struct btrfs_super_block *selected_super;
+	struct btrfs_fs_info *fs_info;
 	struct btrfs_device *device;
-	struct btrfsic_dev_state *selected_dev_state = NULL;
 	int ret = 0;
 	int pass;
 
-	BUG_ON(NULL == state);
+	if (!state)
+		return -EINVAL;
+
+	fs_info = state->fs_info;
 	selected_super = kzalloc(sizeof(*selected_super), GFP_NOFS);
 	if (NULL == selected_super) {
 		pr_info("btrfsic: error, kmalloc failed!\n");
-- 
2.20.1

Re: [PATCH] btrfs: Fix incorrect check

[Markus Elfring]

> The patch fixes this issue by returning an error if state is NULL
> and then assigns fs_info.

Please improve the change message (besides avoiding a typo in the subject).

Would you like to add the tag “Fixes”?

Regards,
Markus

Re: [PATCH] btrfs: Fix incorrect check causing NULL pointer derefernce

[David Sterba]

On Sun, Dec 15, 2019 at 11:32:26AM -0600, Aditya Pakki wrote:
> In btrfsic_process_superblock, argument state is dereferenced for
> the variable fs_info and then checked for NULL. The patch fixes
> this issue by returning an error if state is NULL and then assigns
> fs_info.
> 
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  fs/btrfs/check-integrity.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
> index 0b52ab4cb964..70d7a05cafad 100644
> --- a/fs/btrfs/check-integrity.c
> +++ b/fs/btrfs/check-integrity.c
> @@ -629,15 +629,18 @@ static struct btrfsic_dev_state *btrfsic_dev_state_hashtable_lookup(dev_t dev,
>  static int btrfsic_process_superblock(struct btrfsic_state *state,
>  				      struct btrfs_fs_devices *fs_devices)
>  {
> -	struct btrfs_fs_info *fs_info = state->fs_info;
> -	struct btrfs_super_block *selected_super;
> +	struct btrfsic_dev_state *selected_dev_state = NULL;
>  	struct list_head *dev_head = &fs_devices->devices;
> +	struct btrfs_super_block *selected_super;
> +	struct btrfs_fs_info *fs_info;
>  	struct btrfs_device *device;
> -	struct btrfsic_dev_state *selected_dev_state = NULL;
>  	int ret = 0;
>  	int pass;
>  
> -	BUG_ON(NULL == state);

A fix for this has already been merged to our development queue. Thanks.