This is a note to let you know that I've just added the patch titled
smackfs: Fix use-after-free in netlbl_catmap_walk()
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
smackfs-fix-use-after-free-in-netlbl_catmap_walk.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 216edc62ab75b4d56805476a075a8090d80b58f1
Author: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Date: Sat Aug 28 23:41:40 2021 -0700
smackfs: Fix use-after-free in netlbl_catmap_walk()
[ Upstream commit 0817534ff9ea809fac1322c5c8c574be8483ea57 ]
Syzkaller reported use-after-free bug as described in [1]. The bug is
triggered when smk_set_cipso() tries to free stale category bitmaps
while there are concurrent reader(s) using the same bitmaps.
Wait for RCU grace period to finish before freeing the category bitmaps
in smk_set_cipso(). This makes sure that there are no more readers using
the stale bitmaps and freeing them should be safe.
[1] https://lore.kernel.org/netdev/000000000000a814c505ca657a4e@xxxxxxxxxx/
Reported-by: syzbot+3f91de0b813cc3d19a80@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 009e83ee2d002..25705a72d31bc 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -859,6 +859,7 @@ static int smk_open_cipso(struct inode *inode, struct file *file)
static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
size_t count, loff_t *ppos, int format)
{
+ struct netlbl_lsm_catmap *old_cat;
struct smack_known *skp;
struct netlbl_lsm_secattr ncats;
char mapcatset[SMK_CIPSOLEN];
@@ -948,9 +949,11 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
rc = smk_netlbl_mls(maplevel, mapcatset, &ncats, SMK_CIPSOLEN);
if (rc >= 0) {
- netlbl_catmap_free(skp->smk_netlabel.attr.mls.cat);
+ old_cat = skp->smk_netlabel.attr.mls.cat;
skp->smk_netlabel.attr.mls.cat = ncats.attr.mls.cat;
skp->smk_netlabel.attr.mls.lvl = ncats.attr.mls.lvl;
+ synchronize_rcu();
+ netlbl_catmap_free(old_cat);
rc = count;
}
