diff options
Diffstat (limited to 'KEYS-Fix-race-between-read-and-revoke.patch')
| -rw-r--r-- | KEYS-Fix-race-between-read-and-revoke.patch | 108 |
1 files changed, 0 insertions, 108 deletions
diff --git a/KEYS-Fix-race-between-read-and-revoke.patch b/KEYS-Fix-race-between-read-and-revoke.patch deleted file mode 100644 index df0d9376b..000000000 --- a/KEYS-Fix-race-between-read-and-revoke.patch +++ /dev/null @@ -1,108 +0,0 @@ -From f144220f72062ed5359e0211f130670c915a12dd Mon Sep 17 00:00:00 2001 -From: David Howells <dhowells@redhat.com> -Date: Mon, 14 Dec 2015 10:36:31 -0500 -Subject: [PATCH] KEYS: Fix race between read and revoke - -There's a race between keyctl_read() and keyctl_revoke(). If the revoke -happens between keyctl_read() checking the validity of a key and the key's -semaphore being taken, then the key type read method will see a revoked key. - -This causes a problem for the user-defined key type because it assumes in -its read method that there will always be a payload in a non-revoked key -and doesn't check for a NULL pointer. - -Fix this by making keyctl_read() check the validity of a key after taking -semaphore instead of before. - -This was discovered by a multithreaded test program generated by syzkaller -(http://github.com/google/syzkaller). Here's a cleaned up version: - - #include <sys/types.h> - #include <keyutils.h> - #include <pthread.h> - void *thr0(void *arg) - { - key_serial_t key = (unsigned long)arg; - keyctl_revoke(key); - return 0; - } - void *thr1(void *arg) - { - key_serial_t key = (unsigned long)arg; - char buffer[16]; - keyctl_read(key, buffer, 16); - return 0; - } - int main() - { - key_serial_t key = add_key("user", "%", "foo", 3, KEY_SPEC_USER_KEYRING); - pthread_t th[5]; - pthread_create(&th[0], 0, thr0, (void *)(unsigned long)key); - pthread_create(&th[1], 0, thr1, (void *)(unsigned long)key); - pthread_create(&th[2], 0, thr0, (void *)(unsigned long)key); - pthread_create(&th[3], 0, thr1, (void *)(unsigned long)key); - pthread_join(th[0], 0); - pthread_join(th[1], 0); - pthread_join(th[2], 0); - pthread_join(th[3], 0); - return 0; - } - -Build as: - - cc -o keyctl-race keyctl-race.c -lkeyutils -lpthread - -Run as: - - while keyctl-race; do :; done - -as it may need several iterations to crash the kernel. The crash can be -summarised as: - - BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 - IP: [<ffffffff81279b08>] user_read+0x56/0xa3 - ... - Call Trace: - [<ffffffff81276aa9>] keyctl_read_key+0xb6/0xd7 - [<ffffffff81277815>] SyS_keyctl+0x83/0xe0 - [<ffffffff815dbb97>] entry_SYSCALL_64_fastpath+0x12/0x6f - -Reported-by: Dmitry Vyukov <dvyukov@google.com> -Signed-off-by: David Howells <dhowells@redhat.com> ---- - security/keys/keyctl.c | 18 +++++++++--------- - 1 file changed, 9 insertions(+), 9 deletions(-) - -diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c -index fb111eafcb89..1c3872aeed14 100644 ---- a/security/keys/keyctl.c -+++ b/security/keys/keyctl.c -@@ -751,16 +751,16 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) - - /* the key is probably readable - now try to read it */ - can_read_key: -- ret = key_validate(key); -- if (ret == 0) { -- ret = -EOPNOTSUPP; -- if (key->type->read) { -- /* read the data with the semaphore held (since we -- * might sleep) */ -- down_read(&key->sem); -+ ret = -EOPNOTSUPP; -+ if (key->type->read) { -+ /* Read the data with the semaphore held (since we might sleep) -+ * to protect against the key being updated or revoked. -+ */ -+ down_read(&key->sem); -+ ret = key_validate(key); -+ if (ret == 0) - ret = key->type->read(key, buffer, buflen); -- up_read(&key->sem); -- } -+ up_read(&key->sem); - } - - error2: --- -2.5.0 - |