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 966d30bf2e388..e26e7fbb89657 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -854,6 +854,7 @@ 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]; @@ -943,9 +944,11 @@ 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; }