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ALSA: compress: fix an integer overflow check

PATCH In review Dan Carpenter 2 participants 2 messages Jul 16, 2014

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Sound Kernel janitors Sound - compressed audio
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Dan Carpenter

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#0 lore raw

PATCH 1/1 ALSA: compress: fix an integer overflow check

I previously added an integer overflow check here but looking at it now, it's still buggy.

The bug happens in snd_compr_allocate_buffer(). We multiply ".fragments" and ".fragment_size" and that doesn't overflow but then we save it in an unsigned int so it truncates the high bits away and we allocate a smaller than expected size.

Fixes b35cc8225845 ('ALSA: compress_core: integer overflow in snd_compr_allocate_buffer()')
Signed-off-by Dan Carpenter <[email protected]>

---
The other option would be to declare buffer_size as size_t instead of an unsigned int. This feels like a safer fix though.

sound/core/compress_offload.c +1 -1
index 7403f34..89028fa 100644
@@ -491,7 +491,7 @@ static int snd_compress_check_input(struct snd_compr_params *params)
 {
 	/* first let's check the buffer parameter's */
 	if (params->buffer.fragment_size == 0 ||
-			params->buffer.fragments > SIZE_MAX / params->buffer.fragment_size)
+	    params->buffer.fragments > INT_MAX / params->buffer.fragment_size)
 		return -EINVAL;
 
 	/* now codec parameters */
#1 lore raw

At Wed, 16 Jul 2014 09:37:04 +0300,

Quoted 9 lines · Dan Carpenter

I previously added an integer overflow check here but looking at it now, it's still buggy.

The bug happens in snd_compr_allocate_buffer(). We multiply ".fragments" and ".fragment_size" and that doesn't overflow but then we save it in an unsigned int so it truncates the high bits away and we allocate a smaller than expected size.

Quoted 5 lines
Fixes b35cc8225845 ('ALSA: compress_core: integer overflow in snd_compr_allocate_buffer()')
Signed-off-by Dan Carpenter <[email protected]>

---
The other option would be to declare buffer_size as size_t instead of an unsigned int. This feels like a safer fix though.

Agreed, I took the patch now as is. Thanks.

Takashi

Quoted 15 lines
sound/core/compress_offload.c +1 -1
index 7403f34..89028fa 100644
@@ -491,7 +491,7 @@ static int snd_compress_check_input(struct snd_compr_params *params)
 {
 	/* first let's check the buffer parameter's */
 	if (params->buffer.fragment_size == 0 ||
-			params->buffer.fragments > SIZE_MAX / params->buffer.fragment_size)
+	    params->buffer.fragments > INT_MAX / params->buffer.fragment_size)
 		return -EINVAL;
 
 	/* now codec parameters */