sound: Prevent buffer overflow in OSS load_mixer_volumes

commit d81a12bc29ae4038770e05dce4ab7f26fd5880fb upstream.

The load_mixer_volumes() function, which can be triggered by
unprivileged users via the SOUND_MIXER_SETLEVELS ioctl, is vulnerable to
a buffer overflow.  Because the provided "name" argument isn't
guaranteed to be NULL terminated at the expected 32 bytes, it's possible
to overflow past the end of the last element in the mixer_vols array.
Further exploitation can result in an arbitrary kernel write (via
subsequent calls to load_mixer_volumes()) leading to privilege
escalation, or arbitrary kernel reads via get_mixer_levels().  In
addition, the strcmp() may leak bytes beyond the mixer_vols array.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/sound/oss/soundcard.c b/sound/oss/soundcard.c
index 2d9c51312622fe4a10ea0bf202f24fb092a895ac..5739d8b918e2511e7b6976b720f23bac7fdd080b 100644 (file)
--- a/sound/oss/soundcard.c
+++ b/sound/oss/soundcard.c
@@ -86,7 +86,7 @@ int *load_mixer_volumes(char *name, int *levels, int present)
        int             i, n;
 
        for (i = 0; i < num_mixer_volumes; i++) {
-               if (strcmp(name, mixer_vols[i].name) == 0) {
+               if (strncmp(name, mixer_vols[i].name, 32) == 0) {
                        if (present)
                                mixer_vols[i].num = i;
                        return mixer_vols[i].levels;
@@ -98,7 +98,7 @@ int *load_mixer_volumes(char *name, int *levels, int present)
        }
        n = num_mixer_volumes++;
 
-       strcpy(mixer_vols[n].name, name);
+       strncpy(mixer_vols[n].name, name, 32);
 
        if (present)
                mixer_vols[n].num = n;