lkml.org 
[lkml]   [2017]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.13 63/85] FS-Cache: fix dereference of NULL user_key_payload
    Date
    4.13-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Biggers <ebiggers@google.com>

    commit d124b2c53c7bee6569d2a2d0b18b4a1afde00134 upstream.

    When the file /proc/fs/fscache/objects (available with
    CONFIG_FSCACHE_OBJECT_LIST=y) is opened, we request a user key with
    description "fscache:objlist", then access its payload. However, a
    revoked key has a NULL payload, and we failed to check for this.
    request_key() *does* skip revoked keys, but there is still a window
    where the key can be revoked before we access its payload.

    Fix it by checking for a NULL payload, treating it like a key which was
    already revoked at the time it was requested.

    Fixes: 4fbf4291aa15 ("FS-Cache: Allow the current state of all objects to be dumped")
    Reviewed-by: James Morris <james.l.morris@oracle.com>
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fscache/object-list.c | 7 +++++++
    1 file changed, 7 insertions(+)

    --- a/fs/fscache/object-list.c
    +++ b/fs/fscache/object-list.c
    @@ -330,6 +330,13 @@ static void fscache_objlist_config(struc
    rcu_read_lock();

    confkey = user_key_payload_rcu(key);
    + if (!confkey) {
    + /* key was revoked */
    + rcu_read_unlock();
    + key_put(key);
    + goto no_config;
    + }
    +
    buf = confkey->data;

    for (len = confkey->datalen - 1; len >= 0; len--) {

    \
     
     \ /
      Last update: 2017-10-24 15:16    [W:3.874 / U:0.760 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site