linux-kernel - [PATCH 3.16 162/202] KEYS: allow reaching the keys quotas exactly

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Message-ID: <lsq.1556377989.307177013@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "James Morris" <james.morris@...rosoft.com>,
        "Eric Biggers" <ebiggers@...gle.com>,
        "David Howells" <dhowells@...hat.com>
Subject: [PATCH 3.16 162/202] KEYS: allow reaching the keys quotas exactly

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@...gle.com>

commit a08bf91ce28ed3ae7b6fef35d843fef8dc8c2cd9 upstream.

If the sysctl 'kernel.keys.maxkeys' is set to some number n, then
actually users can only add up to 'n - 1' keys.  Likewise for
'kernel.keys.maxbytes' and the root_* versions of these sysctls.  But
these sysctls are apparently supposed to be *maximums*, as per their
names and all documentation I could find -- the keyrings(7) man page,
Documentation/security/keys/core.rst, and all the mentions of EDQUOT
meaning that the key quota was *exceeded* (as opposed to reached).

Thus, fix the code to allow reaching the quotas exactly.

Fixes: 0b77f5bfb45c ("keys: make the keyring quotas controllable through /proc/sys")
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: James Morris <james.morris@...rosoft.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 security/keys/key.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -260,8 +260,8 @@ struct key *key_alloc(struct key_type *t

 		spin_lock(&user->lock);
 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
-			if (user->qnkeys + 1 >= maxkeys ||
-			    user->qnbytes + quotalen >= maxbytes ||
+			if (user->qnkeys + 1 > maxkeys ||
+			    user->qnbytes + quotalen > maxbytes ||
 			    user->qnbytes + quotalen < user->qnbytes)
 				goto no_quota;
 		}