| From 5d18c28f3772ff5c041b1c4f4997e9340d554574 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Sat, 28 Aug 2021 23:41:40 -0700 |
| Subject: smackfs: Fix use-after-free in netlbl_catmap_walk() |
| |
| From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> |
| |
| [ 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@google.com/ |
| |
| Reported-by: syzbot+3f91de0b813cc3d19a80@syzkaller.appspotmail.com |
| Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> |
| Signed-off-by: Casey Schaufler <casey@schaufler-ca.com> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| security/smack/smackfs.c | 5 ++++- |
| 1 file changed, 4 insertions(+), 1 deletion(-) |
| |
| diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c |
| index 3823ab2c4e4be..cec3f56739dc2 100644 |
| --- a/security/smack/smackfs.c |
| +++ b/security/smack/smackfs.c |
| @@ -831,6 +831,7 @@ 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]; |
| @@ -920,9 +921,11 @@ 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; |
| } |
| |
| -- |
| 2.33.0 |
| |
