lkml.org 
[lkml]   [2021]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.9 062/207] smackfs: Fix use-after-free in netlbl_catmap_walk()
    Date
    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;
    }

    --
    2.33.0


    \
     
     \ /
      Last update: 2021-11-24 13:40    [W:4.196 / U:0.064 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site