diff options
| author | Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2021-08-29 08:41:40 +0200 |
|---|---|---|
| committer | Casey Schaufler <casey@schaufler-ca.com> | 2021-09-16 01:42:25 +0200 |
| commit | 0817534ff9ea809fac1322c5c8c574be8483ea57 (patch) | |
| tree | a76cf7ab4439063bbeb1620c50cf6a9c7ec5f1d5 | |
| parent | Linux 5.15-rc1 (diff) | |
| download | linux-0817534ff9ea809fac1322c5c8c574be8483ea57.tar.xz linux-0817534ff9ea809fac1322c5c8c574be8483ea57.zip | |
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>
| -rw-r--r-- | security/smack/smackfs.c | 5 |
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. |