The snd_seq_ioctl_get_subscription() retrieves the port subscriber information as a pointer, while the object isn't protected, hence it may be deleted before the actual reference. This race was spotted by syzkaller and may lead to a UAF.
The fix is simply copying the data in the lookup function that performs in the rwsem to protect against the deletion.
Reported-by: syzbot+9437020c82413d00222d@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/seq/seq_clientmgr.c | 10 ++-------- sound/core/seq/seq_ports.c | 13 ++++++++----- sound/core/seq/seq_ports.h | 5 +++-- 3 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 976404691261..f256704dc401 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1897,20 +1897,14 @@ static int snd_seq_ioctl_get_subscription(struct snd_seq_client *client, int result; struct snd_seq_client *sender = NULL; struct snd_seq_client_port *sport = NULL; - struct snd_seq_subscribers *p;
result = -EINVAL; if ((sender = snd_seq_client_use_ptr(subs->sender.client)) == NULL) goto __end; if ((sport = snd_seq_port_use_ptr(sender, subs->sender.port)) == NULL) goto __end; - p = snd_seq_port_get_subscription(&sport->c_src, &subs->dest); - if (p) { - result = 0; - *subs = p->info; - } else - result = -ENOENT; - + result = snd_seq_port_get_subscription(&sport->c_src, &subs->dest, + subs); __end: if (sport) snd_seq_port_unlock(sport); diff --git a/sound/core/seq/seq_ports.c b/sound/core/seq/seq_ports.c index 1e2239240f21..d964d728681e 100644 --- a/sound/core/seq/seq_ports.c +++ b/sound/core/seq/seq_ports.c @@ -632,20 +632,23 @@ int snd_seq_port_disconnect(struct snd_seq_client *connector,
/* get matched subscriber */ -struct snd_seq_subscribers *snd_seq_port_get_subscription(struct snd_seq_port_subs_info *src_grp, - struct snd_seq_addr *dest_addr) +int snd_seq_port_get_subscription(struct snd_seq_port_subs_info *src_grp, + struct snd_seq_addr *dest_addr, + struct snd_seq_port_subscribe *subs) { - struct snd_seq_subscribers *s, *found = NULL; + struct snd_seq_subscribers *s; + int err = -ENOENT;
down_read(&src_grp->list_mutex); list_for_each_entry(s, &src_grp->list_head, src_list) { if (addr_match(dest_addr, &s->info.dest)) { - found = s; + *subs = s->info; + err = 0; break; } } up_read(&src_grp->list_mutex); - return found; + return err; }
/* diff --git a/sound/core/seq/seq_ports.h b/sound/core/seq/seq_ports.h index 26bd71f36c41..06003b36652e 100644 --- a/sound/core/seq/seq_ports.h +++ b/sound/core/seq/seq_ports.h @@ -135,7 +135,8 @@ int snd_seq_port_subscribe(struct snd_seq_client_port *port, struct snd_seq_port_subscribe *info);
/* get matched subscriber */ -struct snd_seq_subscribers *snd_seq_port_get_subscription(struct snd_seq_port_subs_info *src_grp, - struct snd_seq_addr *dest_addr); +int snd_seq_port_get_subscription(struct snd_seq_port_subs_info *src_grp, + struct snd_seq_addr *dest_addr, + struct snd_seq_port_subscribe *subs);
#endif