linux-kernel - [PATCH 5.6 109/254] KEYS: reaching the keys quotas correctly

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Message-Id: <20200416131339.774836863@linuxfoundation.org>
Date:   Thu, 16 Apr 2020 15:23:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        Yang Xu <xuyang2018.jy@...fujitsu.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 5.6 109/254] KEYS: reaching the keys quotas correctly

From: Yang Xu <xuyang2018.jy@...fujitsu.com>

commit 2e356101e72ab1361821b3af024d64877d9a798d upstream.

Currently, when we add a new user key, the calltrace as below:

add_key()
  key_create_or_update()
    key_alloc()
    __key_instantiate_and_link
      generic_key_instantiate
        key_payload_reserve
          ......

Since commit a08bf91ce28e ("KEYS: allow reaching the keys quotas exactly"),
we can reach max bytes/keys in key_alloc, but we forget to remove this
limit when we reserver space for payload in key_payload_reserve. So we
can only reach max keys but not max bytes when having delta between plen
and type->def_datalen. Remove this limit when instantiating the key, so we
can keep consistent with key_alloc.

Also, fix the similar problem in keyctl_chown_key().

Fixes: 0b77f5bfb45c ("keys: make the keyring quotas controllable through /proc/sys")
Fixes: a08bf91ce28e ("KEYS: allow reaching the keys quotas exactly")
Cc: stable@...r.kernel.org # 5.0.x
Cc: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Yang Xu <xuyang2018.jy@...fujitsu.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Reviewed-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/keys/key.c    |    2 +-
 security/keys/keyctl.c |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -382,7 +382,7 @@ int key_payload_reserve(struct key *key,
 		spin_lock(&key->user->lock);
 
 		if (delta > 0 &&
-		    (key->user->qnbytes + delta >= maxbytes ||
+		    (key->user->qnbytes + delta > maxbytes ||
 		     key->user->qnbytes + delta < key->user->qnbytes)) {
 			ret = -EDQUOT;
 		}
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -937,8 +937,8 @@ long keyctl_chown_key(key_serial_t id, u
 				key_quota_root_maxbytes : key_quota_maxbytes;
 
 			spin_lock(&newowner->lock);
-			if (newowner->qnkeys + 1 >= maxkeys ||
-			    newowner->qnbytes + key->quotalen >= maxbytes ||
+			if (newowner->qnkeys + 1 > maxkeys ||
+			    newowner->qnbytes + key->quotalen > maxbytes ||
 			    newowner->qnbytes + key->quotalen <
 			    newowner->qnbytes)
 				goto quota_overrun;