This is a note to let you know that I've just added the patch titled ALSA: gus: fix null pointer dereference on pointer block to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-gus-fix-null-pointer-dereference-on-pointer-blo.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 4334357f734e4f0912dd169dbc60e0e9419ace63 Author: Chengfeng Ye <cyeaa@xxxxxxxxxxxxxx> Date: Sun Oct 24 03:46:11 2021 -0700 ALSA: gus: fix null pointer dereference on pointer block [ Upstream commit a0d21bb3279476c777434c40d969ea88ca64f9aa ] The pointer block return from snd_gf1_dma_next_block could be null, so there is a potential null pointer dereference issue. Fix this by adding a null check before dereference. Signed-off-by: Chengfeng Ye <cyeaa@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20211024104611.9919-1-cyeaa@xxxxxxxxxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/sound/isa/gus/gus_dma.c b/sound/isa/gus/gus_dma.c index 36c27c8323601..2e27cd3427c87 100644 --- a/sound/isa/gus/gus_dma.c +++ b/sound/isa/gus/gus_dma.c @@ -141,6 +141,8 @@ static void snd_gf1_dma_interrupt(struct snd_gus_card * gus) } block = snd_gf1_dma_next_block(gus); spin_unlock(&gus->dma_lock); + if (!block) + return; snd_gf1_dma_program(gus, block->addr, block->buf_addr, block->count, (unsigned short) block->cmd); kfree(block); #if 0