2022-08-24 08:22:03

by Zheyu Ma

Subject: [PATCH] ALSA: control: Fix an out-of-bounds bug in get_ctl_id_hash()

Since the user can control the arguments provided to the kernel by the
ioctl() system call, an out-of-bounds bug occurs when the 'id->name'
provided by the user does not end with '\0'.

The following log can reveal it:

[ 10.002313] BUG: KASAN: stack-out-of-bounds in snd_ctl_find_id+0x36c/0x3a0
[ 10.002895] Read of size 1 at addr ffff888109f5fe28 by task snd/439
[ 10.004934] Call Trace:
[ 10.007140] snd_ctl_find_id+0x36c/0x3a0
[ 10.007489] snd_ctl_ioctl+0x6cf/0x10e0

Fix this by checking the bound of 'id->name' in the loop.

Fixes: c27e1efb61c5 ("ALSA: control: Use xarray for faster lookups")
Signed-off-by: Zheyu Ma <[email protected]>
---
sound/core/control.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sound/core/control.c b/sound/core/control.c
index f3e893715369..e8fc4c511e5f 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -385,14 +385,14 @@ static bool elem_id_matches(const struct snd_kcontrol *kctl,
#define MULTIPLIER 37
static unsigned long get_ctl_id_hash(const struct snd_ctl_elem_id *id)
{
+ int i;
unsigned long h;
- const unsigned char *p;

h = id->iface;
h = MULTIPLIER * h + id->device;
h = MULTIPLIER * h + id->subdevice;
- for (p = id->name; *p; p++)
- h = MULTIPLIER * h + *p;
+ for (i = 0; id->name[i] && i < SNDRV_CTL_ELEM_ID_NAME_MAXLEN; i++)
+ h = MULTIPLIER * h + id->name[i];
h = MULTIPLIER * h + id->index;
h &= LONG_MAX;
return h;
--
2.25.1

2022-08-24 09:59:59

by Takashi Iwai

Subject: Re: [PATCH] ALSA: control: Fix an out-of-bounds bug in get_ctl_id_hash()

On Wed, 24 Aug 2022 10:16:54 +0200,
Zheyu Ma wrote:
>
> Since the user can control the arguments provided to the kernel by the
> ioctl() system call, an out-of-bounds bug occurs when the 'id->name'
> provided by the user does not end with '\0'.
>
> The following log can reveal it:
>
> [ 10.002313] BUG: KASAN: stack-out-of-bounds in snd_ctl_find_id+0x36c/0x3a0
> [ 10.002895] Read of size 1 at addr ffff888109f5fe28 by task snd/439
> [ 10.004934] Call Trace:
> [ 10.007140] snd_ctl_find_id+0x36c/0x3a0
> [ 10.007489] snd_ctl_ioctl+0x6cf/0x10e0
>
> Fix this by checking the bound of 'id->name' in the loop.
>
> Fixes: c27e1efb61c5 ("ALSA: control: Use xarray for faster lookups")
> Signed-off-by: Zheyu Ma <[email protected]>

Thanks, applied now.


Takashi