KEYS: fix parsing invalid pkey info string

We need to check the return value of match_token() for Opt_err before
doing anything with it.

[ Not only did the old "-1" value for Opt_err cause problems for the
  __test_and_set_bit(), as fixed in commit 94c13f66e13c ("security:
  don't use a negative Opt_err token index"), but accessing
  "args[0].from" is invalid for the Opt_err case, as pointed out by Eric
  later.  - Linus ]

Reported-by: syzbot+a22e0dc07567662c50bc@syzkaller.appspotmail.com
Fixes: 00d60fd3b932 ("KEYS: Provide keyctls to drive the new key type ops for asymmetric keys [ver #2]")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Cc: stable@kernel.org # 4.20
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/security/keys/keyctl_pkey.c b/security/keys/keyctl_pkey.c
index 70e65a2..8bdea5a 100644 (file)
--- a/security/keys/keyctl_pkey.c
+++ b/security/keys/keyctl_pkey.c
@@ -50,6 +50,8 @@ static int keyctl_pkey_params_parse(struct kernel_pkey_params *params)
                if (*p == '\0' || *p == ' ' || *p == '\t')
                        continue;
                token = match_token(p, param_keys, args);
+               if (token == Opt_err)
+                       return -EINVAL;
                if (__test_and_set_bit(token, &token_mask))
                        return -EINVAL;
                q = args[0].from;