On Wed, 23 Nov 2022 08:06:16 +0100, butt3rflyh4ck wrote: > > 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. Other members are initialized with zero. https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html Takashi > > > Regards, > butt3rflyh4ck. > > On Wed, Nov 23, 2022 at 2:55 PM Takashi Iwai <tiwai@xxxxxxx> 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@xxxxxxxxx> > > > > > > --- > > > > > > Reason for resend: > > > 1. 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 > > > > -- > Active Defense Lab of Venustech >