Hi, the compat_status structure is struct compat_snd_rawmidi_status64 { s32 stream; u8 rsvd[4]; /* alignment */ s64 tstamp_sec; s64 tstamp_nsec; u32 avail; u32 xruns; unsigned char reserved[16]; } __attribute__((packed)); The rsvd[4] and reserved[16] are not initialized.
Regards, butt3rflyh4ck.
On Wed, Nov 23, 2022 at 2:55 PM Takashi Iwai tiwai@suse.de wrote:
On Wed, 23 Nov 2022 06:09:11 +0100, Xiaolong Huang wrote:
The compat_status is declared off of the stack, so it needs to be zeroed out before copied back to userspace to prevent any unintentional data leakage.
Fixes: d9e5582c4bb2 ("ALSA: Avoid using timespec for struct snd_rawmidi_status") Signed-off-by: Xiaolong Huang butterflyhuangxx@gmail.com
Reason for resend:
- add Fixes line.
sound/core/rawmidi_compat.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/sound/core/rawmidi_compat.c b/sound/core/rawmidi_compat.c index 68a93443583c..6afa68165b17 100644 --- a/sound/core/rawmidi_compat.c +++ b/sound/core/rawmidi_compat.c @@ -80,6 +80,7 @@ static int snd_rawmidi_ioctl_status_compat64(struct snd_rawmidi_file *rfile, if (err < 0) return err;
memset(&compat_status, 0, sizeof(compat_status)); compat_status = (struct compat_snd_rawmidi_status64) { .stream = status.stream, .tstamp_sec = status.tstamp_sec,Here at the line just after your addition, compat_status is fully initialized by substitution, so I believe the memset is superfluous.
Or have you verified that it really leaks the uninitialized memory?
thanks,
Takashi