linux-kernel - [PATCH] KEYS: allow reaching the keys quotas exactly

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Message-Id: <20190211211010.220098-1-ebiggers@kernel.org>
Date:   Mon, 11 Feb 2019 13:10:10 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     keyrings@...r.kernel.org, David Howells <dhowells@...hat.com>
Cc:     linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] KEYS: allow reaching the keys quotas exactly

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

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")
Cc: <stable@...r.kernel.org> # v2.6.26+
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 security/keys/key.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/keys/key.c b/security/keys/key.c
index 44a80d6741a1..0ec9322af4f9 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -265,8 +265,8 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 
 		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;
 		}
-- 
2.20.1.791.gb4d0f1c61a-goog