[PATCH] configfs: fix memleak in configfs_release_bin_file

[PATCH] configfs: fix memleak in configfs_release_bin_file

[Chung-Chiang Cheng]

When reading binary attributes in progress, buffer->bin_buffer is setup in
configfs_read_bin_file() but never freed.

Fixes: 03607ace807b4 ("configfs: implement binary attributes")
Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>
---
 fs/configfs/file.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index e26060dae70a..cdd23f4a51c8 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -466,9 +466,13 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
 {
 	struct configfs_buffer *buffer = file->private_data;
 
-	buffer->read_in_progress = false;
-
-	if (buffer->write_in_progress) {
+	if (buffer->read_in_progress) {
+		buffer->read_in_progress = false;
+		vfree(buffer->bin_buffer);
+		buffer->bin_buffer = NULL;
+		buffer->bin_buffer_size = 0;
+		buffer->needs_read_fill = 1;
+	} else if (buffer->write_in_progress) {
 		struct configfs_fragment *frag = to_frag(file);
 		buffer->write_in_progress = false;
 
-- 
2.25.1

Re: [PATCH] configfs: fix memleak in configfs_release_bin_file

[Christoph Hellwig]

Hmm.  The issue looks real, but I think we should just call the vfree
unconditionally given that the buffer structure is zeroed on allocation
and freed just after, and also remove the pointless clearing of all the
flags.  Does something like this work for you?

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
index 53913b84383a..1ab6afb84f04 100644
--- a/fs/configfs/file.c
+++ b/fs/configfs/file.c
@@ -393,11 +393,8 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
 {
 	struct configfs_buffer *buffer = file->private_data;
 
-	buffer->read_in_progress = false;
-
 	if (buffer->write_in_progress) {
 		struct configfs_fragment *frag = to_frag(file);
-		buffer->write_in_progress = false;
 
 		down_read(&frag->frag_sem);
 		if (!frag->frag_dead) {
@@ -407,13 +404,9 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
 					buffer->bin_buffer_size);
 		}
 		up_read(&frag->frag_sem);
-		/* vfree on NULL is safe */
-		vfree(buffer->bin_buffer);
-		buffer->bin_buffer = NULL;
-		buffer->bin_buffer_size = 0;
-		buffer->needs_read_fill = 1;
 	}
 
+	vfree(buffer->bin_buffer);
 	configfs_release(inode, file);
 	return 0;
 }

Re: [PATCH] configfs: fix memleak in configfs_release_bin_file

[Chung-Chiang Cheng]

It works for me. I've verified it with ACPI configfs that is the only
one using configfs binary attributes so far, and the memleak issue
is solved.

On Tue, Jun 22, 2021 at 2:04 PM Christoph Hellwig <hch@lst.de> wrote:
>
> Hmm.  The issue looks real, but I think we should just call the vfree
> unconditionally given that the buffer structure is zeroed on allocation
> and freed just after, and also remove the pointless clearing of all the
> flags.  Does something like this work for you?
>
> diff --git a/fs/configfs/file.c b/fs/configfs/file.c
> index 53913b84383a..1ab6afb84f04 100644
> --- a/fs/configfs/file.c
> +++ b/fs/configfs/file.c
> @@ -393,11 +393,8 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
>  {
>         struct configfs_buffer *buffer = file->private_data;
>
> -       buffer->read_in_progress = false;
> -
>         if (buffer->write_in_progress) {
>                 struct configfs_fragment *frag = to_frag(file);
> -               buffer->write_in_progress = false;
>
>                 down_read(&frag->frag_sem);
>                 if (!frag->frag_dead) {
> @@ -407,13 +404,9 @@ static int configfs_release_bin_file(struct inode *inode, struct file *file)
>                                         buffer->bin_buffer_size);
>                 }
>                 up_read(&frag->frag_sem);
> -               /* vfree on NULL is safe */
> -               vfree(buffer->bin_buffer);
> -               buffer->bin_buffer = NULL;
> -               buffer->bin_buffer_size = 0;
> -               buffer->needs_read_fill = 1;
>         }
>
> +       vfree(buffer->bin_buffer);
>         configfs_release(inode, file);
>         return 0;
>  }

Re: [PATCH] configfs: fix memleak in configfs_release_bin_file

[Christoph Hellwig]

Thanks.  I'v split this into one to move the vfree attribute to you
and a cleanup on top and applied the result to the configfs tree:

http://git.infradead.org/users/hch/configfs.git/shortlog/refs/heads/for-next