UPSTREAM: KEYS: Fix keyring ref leak in join_session_keyring()
Yevgeny Pats [Tue, 19 Jan 2016 22:09:04 +0000 (22:09 +0000)]
(cherry pick from commit 23567fd052a9abb6d67fe8e7a9ccdd9800a540f2)

This fixes CVE-2016-0728.

If a thread is asked to join as a session keyring the keyring that's already
set as its session, we leak a keyring reference.

This can be tested with the following program:

#include <stddef.h>
#include <stdio.h>
#include <sys/types.h>
#include <keyutils.h>

int main(int argc, const char *argv[])
{
int i = 0;
key_serial_t serial;

serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
"leaked-keyring");
if (serial < 0) {
perror("keyctl");
return -1;
}

if (keyctl(KEYCTL_SETPERM, serial,
   KEY_POS_ALL | KEY_USR_ALL) < 0) {
perror("keyctl");
return -1;
}

for (i = 0; i < 100; i++) {
serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
"leaked-keyring");
if (serial < 0) {
perror("keyctl");
return -1;
}
}

return 0;
}

If, after the program has run, there something like the following line in
/proc/keys:

3f3d898f I--Q---   100 perm 3f3f0000     0     0 keyring   leaked-keyring: empty

with a usage count of 100 * the number of times the program has been run,
then the kernel is malfunctioning.  If leaked-keyring has zero usages or
has been garbage collected, then the problem is fixed.

Bug 1720836

Reported-by: Yevgeny Pats <yevgeny@perception-point.io>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Change-Id: I10177a58a7b3178eda95017557edaa7298594d06
(cherry picked from commit 9fc5f368bb89b65b591c4f800dfbcc7432e49de5)
Signed-off-by: Sumit Singh <sumsingh@nvidia.com>
Reviewed-on: http://git-master/r/935565
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
(cherry picked from commit 07be7f19b4c356ce94642d0c2cecb93179a9a9bc)
Signed-off-by: Todd Poynter <tpoynter@nvidia.com>
Reviewed-on: http://git-master/r/936979
(cherry picked from commit 2af5d2a42a8da43f466aed81941174219470486b)
Signed-off-by: Toby Butzon <tbutzon@nvidia.com>
Reviewed-on: http://git-master/r/1031380
Reviewed-by: Vinayak Pane <vpane@nvidia.com>
Reviewed-by: Manish Tuteja <mtuteja@nvidia.com>

security/keys/process_keys.c

index 42defae..cd871dc 100644 (file)
@@ -792,6 +792,7 @@ long join_session_keyring(const char *name)
                ret = PTR_ERR(keyring);
                goto error2;
        } else if (keyring == new->session_keyring) {
+               key_put(keyring);
                ret = 0;
                goto error2;
        }