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    Subject[PATCH 4.20 018/183] KEYS: allow reaching the keys quotas exactly
    Date
    4.20-stable review patch.  If anyone has any objections, please let me know.

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

    From: Eric Biggers <ebiggers@google.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")
    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>

    ---
    security/keys/key.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/security/keys/key.c
    +++ b/security/keys/key.c
    @@ -265,8 +265,8 @@ 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;
    }

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