KEYS: allow reaching the keys quotas exactly

BugLink: https://bugs.launchpad.net/bugs/1837813
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")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/security/keys/key.c b/security/keys/key.c
index d97c9394b5dd4f7479e9211a2dbb236503e05d2b..249a6da4d27701be2ba416e8451a7edea0cbd5b4 100644 (file)
--- 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;
                }