UPSTREAM: KEYS: Fix keyring ref leak in join_session_keyring()
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.
Reported-by: Yevgeny Pats <[email protected]>
Signed-off-by: David Howells <[email protected]>
Acked-by: Don Zickus <[email protected]>
Acked-by: Prarit Bhargava <[email protected]>
Acked-by: Jarod Wilson <[email protected]>
Signed-off-by: James Morris <[email protected]>
Bug: 26692844
(cherry picked from commit 23567fd052a9abb6d67fe8e7a9ccdd9800a540f2)
Signed-off-by: Kees Cook <[email protected]>
Change-Id: I8e82764df4f20ffb3f0a1f0a0784d913dda6fa68
1 file changed
