[PATCH 5.15 049/917] ALSA: PCM: Fix NULL dereference at mmap checks

Greg Kroah-Hartman
2021-11-15T23:27:56Z

From: Takashi Iwai <tiwai@suse.de>

commit 8e537d5dec34cac746dd6abf6a83e5de3aa471fc upstream.

The recent refactoring of mmap handling caused Oops on some devices
that don't use the standard memory allocations. This patch addresses
it by allowing snd_dma_buffer_mmap() helper to receive the NULL
pointer dmab argument (and return an error appropriately).

Fixes: a202bd1ad86d ("ALSA: core: Move mmap handler into memalloc ops")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211107163911.13534-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/memalloc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -176,8 +176,11 @@ EXPORT_SYMBOL_GPL(snd_devm_alloc_pages);
int snd_dma_buffer_mmap(struct snd_dma_buffer *dmab,
struct vm_area_struct *area)
{
- const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
+ const struct snd_malloc_ops *ops;

+ if (!dmab)
+ return -ENOENT;
+ ops = snd_dma_get_ops(dmab);
if (ops && ops->mmap)
return ops->mmap(dmab, area);
else