Patchwork e2fsprogs: fix memory leak in ext2fs_free_generic_bmap()

login
register
mail settings
Submitter Lukas Czerner
Date March 21, 2011, 10:14 a.m.
Message ID <1300702440-4835-1-git-send-email-lczerner@redhat.com>
Download mbox | patch
Permalink /patch/87735/
State Superseded
Headers show

Comments

Lukas Czerner - March 21, 2011, 10:14 a.m.
In ext2fs_free_generic_bmap() when we are freeing 64-bit bitmap, we do
call free_bmap() to free backend specific bitmap structures, however we
should also free ext2fs_generic_bitmap structure as well. So this commit
fixes that and removes unnecessary assignments.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
 lib/ext2fs/gen_bitmap64.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
Theodore Ts'o - May 8, 2011, 10:10 p.m.
On Mon, Mar 21, 2011 at 11:14:00AM +0100, Lukas Czerner wrote:
> In ext2fs_free_generic_bmap() when we are freeing 64-bit bitmap, we do
> call free_bmap() to free backend specific bitmap structures, however we
> should also free ext2fs_generic_bitmap structure as well. So this commit
> fixes that and removes unnecessary assignments.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> ---
>  lib/ext2fs/gen_bitmap64.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
> index 8b9e4c5..f343cc7 100644
> --- a/lib/ext2fs/gen_bitmap64.c
> +++ b/lib/ext2fs/gen_bitmap64.c
> @@ -153,11 +153,11 @@ void ext2fs_free_generic_bmap(ext2fs_generic_bitmap bmap)
>  
>  	bmap->bitmap_ops->free_bmap(bmap);
>  
> -	if (bmap->description) {
> +	if (bmap->description)
>  		ext2fs_free_mem(&bmap->description);
> -		bmap->description = 0;
> -	}
> -	bmap->magic = 0;
> +
> +	ext2fs_free_mem(&bmap);
> +	bmap = NULL;

Setting bmap to NULL is pointless since C doesn't have
pass-by-reference ala C++ (i.e., it's not like this function parameter
is declared "ext2fs_generic_bitmap &bmap").

So it's actually a good idea to zap bmap->description, and especially
bmap->magic, since that will allow us to catch attempts to use the
bitmap after we free it.

I'll make the simplification of your patch which just adds the missing
"ext2fs_free_mem(&bmap)" call.

					- Ted
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Lukas Czerner - May 9, 2011, 8:09 a.m.
On Sun, 8 May 2011, Ted Ts'o wrote:

> On Mon, Mar 21, 2011 at 11:14:00AM +0100, Lukas Czerner wrote:
> > In ext2fs_free_generic_bmap() when we are freeing 64-bit bitmap, we do
> > call free_bmap() to free backend specific bitmap structures, however we
> > should also free ext2fs_generic_bitmap structure as well. So this commit
> > fixes that and removes unnecessary assignments.
> > 
> > Signed-off-by: Lukas Czerner <lczerner@redhat.com>
> > ---
> >  lib/ext2fs/gen_bitmap64.c |    8 ++++----
> >  1 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
> > index 8b9e4c5..f343cc7 100644
> > --- a/lib/ext2fs/gen_bitmap64.c
> > +++ b/lib/ext2fs/gen_bitmap64.c
> > @@ -153,11 +153,11 @@ void ext2fs_free_generic_bmap(ext2fs_generic_bitmap bmap)
> >  
> >  	bmap->bitmap_ops->free_bmap(bmap);
> >  
> > -	if (bmap->description) {
> > +	if (bmap->description)
> >  		ext2fs_free_mem(&bmap->description);
> > -		bmap->description = 0;
> > -	}
> > -	bmap->magic = 0;
> > +
> > +	ext2fs_free_mem(&bmap);
> > +	bmap = NULL;
> 
> Setting bmap to NULL is pointless since C doesn't have
> pass-by-reference ala C++ (i.e., it's not like this function parameter
> is declared "ext2fs_generic_bitmap &bmap").
> 
> So it's actually a good idea to zap bmap->description, and especially
> bmap->magic, since that will allow us to catch attempts to use the
> bitmap after we free it.
> 
> I'll make the simplification of your patch which just adds the missing
> "ext2fs_free_mem(&bmap)" call.
> 
> 					- Ted
> 

Agh, you're right, sorry about that.

Thanks!
-Lukas
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
index 8b9e4c5..f343cc7 100644
--- a/lib/ext2fs/gen_bitmap64.c
+++ b/lib/ext2fs/gen_bitmap64.c
@@ -153,11 +153,11 @@  void ext2fs_free_generic_bmap(ext2fs_generic_bitmap bmap)
 
 	bmap->bitmap_ops->free_bmap(bmap);
 
-	if (bmap->description) {
+	if (bmap->description)
 		ext2fs_free_mem(&bmap->description);
-		bmap->description = 0;
-	}
-	bmap->magic = 0;
+
+	ext2fs_free_mem(&bmap);
+	bmap = NULL;
 }
 
 errcode_t ext2fs_copy_generic_bmap(ext2fs_generic_bitmap src,