ALSA: rawmidi: Fix missing input substream checks in compat ioctls

commit 8a56ef4f3ffba9ebf4967b61ef600b0a7ba10f11 upstream.

Some rawmidi compat ioctls lack of the input substream checks
(although they do check only for rfile->output).  This many eventually
lead to an Oops as NULL substream is passed to the rawmidi core
functions.

Fix it by adding the proper checks before each function call.

The bug was spotted by syzkaller.

Reported-by: syzbot+f7a0348affc3b67bc617@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/core/rawmidi_compat.c b/sound/core/rawmidi_compat.c
index 09a89094dcf72b3c8bf7ded51a8f723f41f8bdc6..4e304a24924a4c6ec8546a166a0ea2c930edb39a 100644 (file)
--- a/sound/core/rawmidi_compat.c
+++ b/sound/core/rawmidi_compat.c
@@ -36,8 +36,6 @@ static int snd_rawmidi_ioctl_params_compat(struct snd_rawmidi_file *rfile,
        struct snd_rawmidi_params params;
        unsigned int val;
 
-       if (rfile->output == NULL)
-               return -EINVAL;
        if (get_user(params.stream, &src->stream) ||
            get_user(params.buffer_size, &src->buffer_size) ||
            get_user(params.avail_min, &src->avail_min) ||
@@ -46,8 +44,12 @@ static int snd_rawmidi_ioctl_params_compat(struct snd_rawmidi_file *rfile,
        params.no_active_sensing = val;
        switch (params.stream) {
        case SNDRV_RAWMIDI_STREAM_OUTPUT:
+               if (!rfile->output)
+                       return -EINVAL;
                return snd_rawmidi_output_params(rfile->output, &params);
        case SNDRV_RAWMIDI_STREAM_INPUT:
+               if (!rfile->input)
+                       return -EINVAL;
                return snd_rawmidi_input_params(rfile->input, &params);
        }
        return -EINVAL;
@@ -67,16 +69,18 @@ static int snd_rawmidi_ioctl_status_compat(struct snd_rawmidi_file *rfile,
        int err;
        struct snd_rawmidi_status status;
 
-       if (rfile->output == NULL)
-               return -EINVAL;
        if (get_user(status.stream, &src->stream))
                return -EFAULT;
 
        switch (status.stream) {
        case SNDRV_RAWMIDI_STREAM_OUTPUT:
+               if (!rfile->output)
+                       return -EINVAL;
                err = snd_rawmidi_output_status(rfile->output, &status);
                break;
        case SNDRV_RAWMIDI_STREAM_INPUT:
+               if (!rfile->input)
+                       return -EINVAL;
                err = snd_rawmidi_input_status(rfile->input, &status);
                break;
        default:
@@ -113,16 +117,18 @@ static int snd_rawmidi_ioctl_status_x32(struct snd_rawmidi_file *rfile,
        int err;
        struct snd_rawmidi_status status;
 
-       if (rfile->output == NULL)
-               return -EINVAL;
        if (get_user(status.stream, &src->stream))
                return -EFAULT;
 
        switch (status.stream) {
        case SNDRV_RAWMIDI_STREAM_OUTPUT:
+               if (!rfile->output)
+                       return -EINVAL;
                err = snd_rawmidi_output_status(rfile->output, &status);
                break;
        case SNDRV_RAWMIDI_STREAM_INPUT:
+               if (!rfile->input)
+                       return -EINVAL;
                err = snd_rawmidi_input_status(rfile->input, &status);
                break;
        default: