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Commit 91b9c23b authored by Pawan Gupta's avatar Pawan Gupta Committed by Greg Kroah-Hartman
Browse files

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@google.com/



Reported-by: default avatar <syzbot+3f91de0b813cc3d19a80@syzkaller.appspotmail.com>
Signed-off-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 31df731c

security/smack/smackfs.c

+4 −1
Original line number Diff line number Diff line
@@ -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;

	}