[PATCH] squashfs: Improve error handling in squashfs_decompressor_create()

[PATCH] squashfs: Improve error handling in squashfs_decompressor_create()

[Markus Elfring]

From: Markus Elfring <elfring@users.sourceforge.net>
Date: Fri, 29 Dec 2023 21:30:26 +0100

The kfree() function was called in two cases by
the squashfs_decompressor_create() function during error handling
even if the passed variable contained a null pointer.
This issue was detected by using the Coccinelle software.

* Thus return directly after a call of the function “kzalloc” failed
  at the beginning.

* Use another label.

* Move an error code assignment into an if branch.

* Delete an initialisation (for the variable “decomp_strm”)
  which became unnecessary with this refactoring.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
---
 fs/squashfs/decompressor_multi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/squashfs/decompressor_multi.c b/fs/squashfs/decompressor_multi.c
index 416c53eedbd1..81fd15d5163c 100644
--- a/fs/squashfs/decompressor_multi.c
+++ b/fs/squashfs/decompressor_multi.c
@@ -62,12 +62,12 @@ static void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
 				void *comp_opts)
 {
 	struct squashfs_stream *stream;
-	struct decomp_stream *decomp_strm = NULL;
-	int err = -ENOMEM;
+	struct decomp_stream *decomp_strm;
+	int err;

 	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
 	if (!stream)
-		goto out;
+		return ERR_PTR(-ENOMEM);

 	stream->comp_opts = comp_opts;
 	mutex_init(&stream->mutex);
@@ -81,8 +81,10 @@ static void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
 	 * file system works.
 	 */
 	decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
-	if (!decomp_strm)
-		goto out;
+	if (!decomp_strm) {
+		err = -ENOMEM;
+		goto free_stream;
+	}

 	decomp_strm->stream = msblk->decompressor->init(msblk,
 						stream->comp_opts);
@@ -97,6 +99,7 @@ static void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,

 out:
 	kfree(decomp_strm);
+free_stream:
 	kfree(stream);
 	return ERR_PTR(err);
 }
--
2.43.0

Re: [PATCH] squashfs: Improve error handling in squashfs_decompressor_create()

[Phillip Lougher]

> On 30/12/2023 09:55 GMT Markus Elfring <markus.elfring@web.de> wrote:
> 
>  
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Fri, 29 Dec 2023 21:30:26 +0100
> 
> The kfree() function was called in two cases by
> the squashfs_decompressor_create() function during error handling
> even if the passed variable contained a null pointer.
> This issue was detected by using the Coccinelle software.
> 
> * Thus return directly after a call of the function “kzalloc” failed
>   at the beginning.
> 
> * Use another label.
> 
> * Move an error code assignment into an if branch.
> 
> * Delete an initialisation (for the variable “decomp_strm”)
>   which became unnecessary with this refactoring.
> 
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>

As mentioned in this thread (and many others)

https://lore.kernel.org/all/20240104204032.GN31813@kernel.org/

calling Kfree with a NULL pointer is perfectly valid.

So like most others I'm going to ignore this patch.

Cheers

Phillip