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authorJulia Lawall <julia@diku.dk>2010-11-09 23:00:41 +0100
committerTakashi Iwai <tiwai@suse.de>2010-11-11 02:03:00 +0100
commitfa2b30af84e84129b8d4cf955890ad167cc20cf0 (patch)
tree2268c3f9d81b2065fd51a881f4f01c75126d9acc /sound/pci
parente9161512017f11050ef2b826cbb10be1673554c6 (diff)
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ALSA: sound/pci/ctxfi/ctpcm.c: Remove potential for use after free
In each function, the value apcm is stored in the private_data field of runtime. At the same time the function ct_atc_pcm_free_substream is stored in the private_free field of the same structure. ct_atc_pcm_free_substream dereferences and ultimately frees the value in the private_data field. But each function can exit in an error case with apcm having been freed, in which case a subsequent call to the private_free function would perform a dereference after free. On the other hand, if the private_free field is not initialized, it is NULL, and not invoked (see snd_pcm_detach_substream in sound/core/pcm.c). To avoid the introduction of a dangling pointer, the initializations of the private_data and private_free fields are moved to the end of the function, past any possible free of apcm. This is safe because the previous calls to snd_pcm_hw_constraint_integer and snd_pcm_hw_constraint_minmax, which take runtime as an argument, do not refer to either of these fields. In each function, there is one error case where apcm needs to be freed, and a call to kfree is added. The sematic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @@ expression e,e1,e2,e3; identifier f,free1,free2; expression a; @@ *e->f = a ... when != e->f = e1 when any if (...) { ... when != free1(...,e,...) when != e->f = e2 * kfree(a) ... when != free2(...,e,...) when != e->f = e3 } // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/pci')
-rw-r--r--sound/pci/ctxfi/ctpcm.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/sound/pci/ctxfi/ctpcm.c b/sound/pci/ctxfi/ctpcm.c
index 85ab43e8921..457d21189b0 100644
--- a/sound/pci/ctxfi/ctpcm.c
+++ b/sound/pci/ctxfi/ctpcm.c
@@ -129,8 +129,6 @@ static int ct_pcm_playback_open(struct snd_pcm_substream *substream)
apcm->substream = substream;
apcm->interrupt = ct_atc_pcm_interrupt;
- runtime->private_data = apcm;
- runtime->private_free = ct_atc_pcm_free_substream;
if (IEC958 == substream->pcm->device) {
runtime->hw = ct_spdif_passthru_playback_hw;
atc->spdif_out_passthru(atc, 1);
@@ -155,8 +153,12 @@ static int ct_pcm_playback_open(struct snd_pcm_substream *substream)
}
apcm->timer = ct_timer_instance_new(atc->timer, apcm);
- if (!apcm->timer)
+ if (!apcm->timer) {
+ kfree(apcm);
return -ENOMEM;
+ }
+ runtime->private_data = apcm;
+ runtime->private_free = ct_atc_pcm_free_substream;
return 0;
}
@@ -278,8 +280,6 @@ static int ct_pcm_capture_open(struct snd_pcm_substream *substream)
apcm->started = 0;
apcm->substream = substream;
apcm->interrupt = ct_atc_pcm_interrupt;
- runtime->private_data = apcm;
- runtime->private_free = ct_atc_pcm_free_substream;
runtime->hw = ct_pcm_capture_hw;
runtime->hw.rate_max = atc->rsr * atc->msr;
@@ -298,8 +298,12 @@ static int ct_pcm_capture_open(struct snd_pcm_substream *substream)
}
apcm->timer = ct_timer_instance_new(atc->timer, apcm);
- if (!apcm->timer)
+ if (!apcm->timer) {
+ kfree(apcm);
return -ENOMEM;
+ }
+ runtime->private_data = apcm;
+ runtime->private_free = ct_atc_pcm_free_substream;
return 0;
}