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Subject[PATCH] KEYS: allow reaching the keys quotas exactly
Date
From: Eric Biggers <ebiggers@google.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@vger.kernel.org> # v2.6.26+
Signed-off-by: Eric Biggers <ebiggers@google.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
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