[PATCH BUGFIX -rc5] Smack: Do not dereference NULL ipc object

["Ahmed S. Darwish" <darwish.07@gmail.com>]

Hi all,

In the SYSV ipc msgctl(),semctl(),shmctl() family, if the user passed
*_INFO as the desired operation, no specific object is meant to be 
controlled and only system-wide information is returned. This leads
to a NULL IPC object in the LSM hooks if the _INFO flag is given.

Avoid dereferencing this NULL pointer in Smack ipc *ctl() methods.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
---

 smack_lsm.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 0241fd3..38d7075 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1508,7 +1508,7 @@ static int smack_shm_associate(struct shmid_kernel *shp, int shmflg)
  */
 static int smack_shm_shmctl(struct shmid_kernel *shp, int cmd)
 {
-	char *ssp = smack_of_shm(shp);
+	char *ssp;
 	int may;
 
 	switch (cmd) {
@@ -1532,6 +1532,7 @@ static int smack_shm_shmctl(struct shmid_kernel *shp, int cmd)
 		return -EINVAL;
 	}
 
+	ssp = smack_of_shm(shp);
 	return smk_curacc(ssp, may);
 }
 
@@ -1616,7 +1617,7 @@ static int smack_sem_associate(struct sem_array *sma, int semflg)
  */
 static int smack_sem_semctl(struct sem_array *sma, int cmd)
 {
-	char *ssp = smack_of_sem(sma);
+	char *ssp;
 	int may;
 
 	switch (cmd) {
@@ -1645,6 +1646,7 @@ static int smack_sem_semctl(struct sem_array *sma, int cmd)
 		return -EINVAL;
 	}
 
+	ssp = smack_of_sem(sma);
 	return smk_curacc(ssp, may);
 }
 
@@ -1730,7 +1732,7 @@ static int smack_msg_queue_associate(struct msg_queue *msq, int msqflg)
  */
 static int smack_msg_queue_msgctl(struct msg_queue *msq, int cmd)
 {
-	char *msp = smack_of_msq(msq);
+	char *msp;
 	int may;
 
 	switch (cmd) {
@@ -1752,6 +1754,7 @@ static int smack_msg_queue_msgctl(struct msg_queue *msq, int cmd)
 		return -EINVAL;
 	}
 
+	msp = smack_of_msq(msq);
 	return smk_curacc(msp, may);
 }
 
Regards,

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com