| From | Ben Hutchings <> | Date | Thu, 28 Dec 2017 17:05:44 +0000 | Subject | [PATCH 3.16 111/204] lib/digsig: fix dereference of NULL user_key_payload |
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3.16.52-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Biggers <ebiggers@google.com>
commit 192cabd6a296cbc57b3d8c05c4c89d87fc102506 upstream.
digsig_verify() requests a user key, then accesses 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 acquire its semaphore.
Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested.
Fixes: 051dbb918c7f ("crypto: digital signature verification support") Reviewed-by: James Morris <james.l.morris@oracle.com> Cc: Dmitry Kasatkin <dmitry.kasatkin@intel.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- lib/digsig.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/lib/digsig.c +++ b/lib/digsig.c @@ -86,6 +86,12 @@ static int digsig_verify_rsa(struct key down_read(&key->sem); ukp = key->payload.data; + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + err = -EKEYREVOKED; + goto err1; + } + if (ukp->datalen < sizeof(*pkh)) goto err1;
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