ipc_addid() initializes kern_ipc_perm.id after having called
ipc_idr_alloc().
Thus a parallel semctl() or msgctl() that uses e.g. MSG_STAT may use
this unitialized value as the return code.
The patch moves all accesses to kern_ipc_perm.id under the spin_lock().
The issues is related to the finding of
syzbot+2827ef6b3385deb07...@syzkaller.appspotmail.com:
syzbot found an issue with kern_ipc_perm.seq
Signed-off-by: Manfred Spraul <manf...@colorfullife.com>
Cc: Dmitry Vyukov <dvyu...@google.com>
Cc: Kees Cook <keesc...@chromium.org>
Reviewed-by: Davidlohr Bueso <dbu...@suse.de>
---
ipc/msg.c | 19 ++++++++++++++-----
ipc/sem.c | 18 +++++++++++++-----
ipc/shm.c | 19 ++++++++++++++-----
3 files changed, 41 insertions(+), 15 deletions(-)
diff --git a/ipc/msg.c b/ipc/msg.c
index 3b6545302598..49358f474fc9 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -491,7 +491,6 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
int cmd, struct msqid64_ds *p)
{
struct msg_queue *msq;
- int id = 0;
int err;
memset(p, 0, sizeof(*p));
@@ -503,7 +502,6 @@ static int msgctl_stat(struct ipc_namespace *ns, int msqid,
err = PTR_ERR(msq);
goto out_unlock;
}
- id = msq->q_perm.id;
} else { /* IPC_STAT */
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
@@ -548,10 +546,21 @@ static int msgctl_stat(struct ipc_namespace *ns, int
msqid,
p->msg_lspid = pid_vnr(msq->q_lspid);
p->msg_lrpid = pid_vnr(msq->q_lrpid);
- ipc_unlock_object(&msq->q_perm);
- rcu_read_unlock();
- return id;
+ if (cmd == IPC_STAT) {
+ /*
+ * As defined in SUS:
+ * Return 0 on success
+ */
+ err = 0;
+ } else {
+ /*
+ * MSG_STAT and MSG_STAT_ANY (both Linux specific)
+ * Return the full id, including the sequence number
+ */
+ err = msq->q_perm.id;
+ }
+ ipc_unlock_object(&msq->q_perm);
out_unlock:
rcu_read_unlock();
return err;
diff --git a/ipc/sem.c b/ipc/sem.c
index 5af1943ad782..d89ce69b2613 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1222,7 +1222,6 @@ static int semctl_stat(struct ipc_namespace *ns, int
semid,
{
struct sem_array *sma;
time64_t semotime;
- int id = 0;
int err;
memset(semid64, 0, sizeof(*semid64));
@@ -1234,7 +1233,6 @@ static int semctl_stat(struct ipc_namespace *ns, int
semid,
err = PTR_ERR(sma);
goto out_unlock;
}
- id = sma->sem_perm.id;
} else { /* IPC_STAT */
sma = sem_obtain_object_check(ns, semid);
if (IS_ERR(sma)) {
@@ -1274,10 +1272,20 @@ static int semctl_stat(struct ipc_namespace *ns, int
semid,
#endif
semid64->sem_nsems = sma->sem_nsems;
+ if (cmd == IPC_STAT) {
+ /*
+ * As defined in SUS:
+ * Return 0 on success
+ */
+ err = 0;
+ } else {
+ /*
+ * SEM_STAT and SEM_STAT_ANY (both Linux specific)
+ * Return the full id, including the sequence number
+ */
+ err = sma->sem_perm.id;
+ }
ipc_unlock_object(&sma->sem_perm);
- rcu_read_unlock();
- return id;
-
out_unlock:
rcu_read_unlock();
return err;
diff --git a/ipc/shm.c b/ipc/shm.c
index 051a3e1fb8df..f3bae59bed08 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -949,7 +949,6 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
int cmd, struct shmid64_ds *tbuf)
{
struct shmid_kernel *shp;
- int id = 0;
int err;
memset(tbuf, 0, sizeof(*tbuf));
@@ -961,7 +960,6 @@ static int shmctl_stat(struct ipc_namespace *ns, int shmid,
err = PTR_ERR(shp);
goto out_unlock;
}
- id = shp->shm_perm.id;
} else { /* IPC_STAT */
shp = shm_obtain_object_check(ns, shmid);
if (IS_ERR(shp)) {
@@ -1011,10 +1009,21 @@ static int shmctl_stat(struct ipc_namespace *ns, int
shmid,
tbuf->shm_lpid = pid_vnr(shp->shm_lprid);
tbuf->shm_nattch = shp->shm_nattch;
- ipc_unlock_object(&shp->shm_perm);
- rcu_read_unlock();
- return id;
+ if (cmd == IPC_STAT) {
+ /*
+ * As defined in SUS:
+ * Return 0 on success
+ */
+ err = 0;
+ } else {
+ /*
+ * SHM_STAT and SHM_STAT_ANY (both Linux specific)
+ * Return the full id, including the sequence number
+ */
+ err = shp->shm_perm.id;
+ }
+ ipc_unlock_object(&shp->shm_perm);
out_unlock:
rcu_read_unlock();
return err;
--
2.17.1
