If a codec is not attached to the sound soc, a NULL deref is possible as a regular user in /sys.
[ 2278.331878] DSS: context saved [ 2278.820343] Unable to handle kernel NULL pointer dereference at virtual address 00000004 [ 2278.828948] pgd = c36040a2 [ 2278.831787] [00000004] *pgd=876c4831, *pte=00000000, *ppte=00000000 [ 2278.838439] Internal error: Oops: 17 [#1] ARM [ 2278.843017] Modules linked in: [ 2278.846221] CPU: 0 PID: 16337 Comm: grep Tainted: G W 4.16.0-rc4-next-20180308 #71 [ 2278.855529] Hardware name: Nokia RX-51 board [ 2278.860015] PC is at soc_codec_reg_show+0x8/0x19c [ 2278.864959] LR is at codec_reg_show+0x28/0x30
Reported-by: Pavel Machek pavel@ucw.cz Signed-off-by: Kees Cook keescook@chromium.org --- No idea if this is the _right_ fix, but it should stop the crash from unprivileged userspace. --- sound/soc/soc-core.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c index 96c44f6576c9..78ad165ad424 100644 --- a/sound/soc/soc-core.c +++ b/sound/soc/soc-core.c @@ -137,6 +137,9 @@ static ssize_t soc_codec_reg_show(struct snd_soc_codec *codec, char *buf, size_t total = 0; loff_t p = 0;
+ if (!codec || !codec->driver) + return 0; + wordsize = min_bytes_needed(codec->driver->reg_cache_size) * 2; regsize = codec->driver->reg_word_size * 2;