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authorPawan Gupta <pawan.kumar.gupta@linux.intel.com>2021-08-29 09:41:40 +0300
committerCasey Schaufler <casey@schaufler-ca.com>2021-09-16 02:42:25 +0300
commit0817534ff9ea809fac1322c5c8c574be8483ea57 (patch)
treea76cf7ab4439063bbeb1620c50cf6a9c7ec5f1d5 /security
parent6880fa6c56601bb8ed59df6c30fd390cc5f6dd8f (diff)
downloadlinux-0817534ff9ea809fac1322c5c8c574be8483ea57.tar.xz
smackfs: Fix use-after-free in netlbl_catmap_walk()
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>
Diffstat (limited to 'security')
-rw-r--r--security/smack/smackfs.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 3a75d2a8f517..9d853c0e55b8 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;
/*
* This mapping may have been cached, so clear the cache.