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Mon, 25 May 2026 19:18:32 -0700 (PDT) Received: from codespaces-78f0a7.mimvmn1ww3huhhjmzljqefhnig.rx.internal.cloudapp.net ([4.240.39.194]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2beb591d07fsm112242735ad.82.2026.05.25.19.18.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 May 2026 19:18:32 -0700 (PDT) From: Muhammad Bilal To: linux-bluetooth@vger.kernel.org Cc: marcel@holtmann.org, luiz.dentz@gmail.com, gregkh@linuxfoundation.org, johan.hedberg@intel.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v1 1/1] Bluetooth: L2CAP: fix heap over-read in l2cap_get_conf_opt Date: Tue, 26 May 2026 02:17:47 +0000 Message-ID: <20260526021747.31634-1-meatuni001@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit l2cap_get_conf_opt() reads opt->val via a switch on opt->len (1, 2, or 4 bytes). opt->len is a remote-controlled u8. All three callers loop on (len >= L2CAP_CONF_OPT_SIZE), so the loop body executes with as few as 2 bytes remaining. A packet ending with opt->len=4 and only 2 bytes left causes get_unaligned_le32(opt->val) to read 4 bytes past the buffer before the caller can act on the return value. Commit 7c9cbd0b5e38 ("Bluetooth: Verify that l2cap_get_conf_opt provides large enough buffer") added a post-call len < 0 guard in each caller, but the over-read fires inside l2cap_get_conf_opt() before that guard is reached. Add a buflen parameter and validate L2CAP_CONF_OPT_SIZE + opt->len <= buflen before any access to opt->val. Return -EINVAL on violation. Update all three callers to capture the return value and break on negative. With the bounds check ensuring the option fits within the remaining buffer, the post-call len < 0 check is no longer needed and is removed. Fixes: 7c9cbd0b5e38 ("Bluetooth: Verify that l2cap_get_conf_opt provides large enough buffer") Cc: stable@vger.kernel.org Signed-off-by: Muhammad Bilal --- net/bluetooth/l2cap_core.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index fdccd62ccca8..6052ffb280ac 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -3051,12 +3051,23 @@ static struct sk_buff *l2cap_build_cmd(struct l2cap_conn *conn, u8 code, } static inline int l2cap_get_conf_opt(void **ptr, int *type, int *olen, - unsigned long *val) + unsigned long *val, size_t buflen) { struct l2cap_conf_opt *opt = *ptr; int len; + /* Guard opt->len dereference: reject if the 2-byte option header + * itself does not fit in the remaining buffer. + */ + if (buflen < L2CAP_CONF_OPT_SIZE) + return -EINVAL; + len = L2CAP_CONF_OPT_SIZE + opt->len; + + /* Reject options whose payload extends past the remaining buffer. */ + if ((size_t)len > buflen) + return -EINVAL; + *ptr += len; *type = opt->type; @@ -3437,9 +3448,11 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data BT_DBG("chan %p", chan); while (len >= L2CAP_CONF_OPT_SIZE) { - len -= l2cap_get_conf_opt(&req, &type, &olen, &val); - if (len < 0) + int optlen = l2cap_get_conf_opt(&req, &type, &olen, &val, len); + + if (optlen < 0) break; + len -= optlen; hint = type & L2CAP_CONF_HINT; type &= L2CAP_CONF_MASK; @@ -3675,9 +3688,11 @@ static int l2cap_parse_conf_rsp(struct l2cap_chan *chan, void *rsp, int len, BT_DBG("chan %p, rsp %p, len %d, req %p", chan, rsp, len, data); while (len >= L2CAP_CONF_OPT_SIZE) { - len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val); - if (len < 0) + int optlen = l2cap_get_conf_opt(&rsp, &type, &olen, &val, len); + + if (optlen < 0) break; + len -= optlen; switch (type) { case L2CAP_CONF_MTU: @@ -3946,9 +3961,11 @@ static void l2cap_conf_rfc_get(struct l2cap_chan *chan, void *rsp, int len) return; while (len >= L2CAP_CONF_OPT_SIZE) { - len -= l2cap_get_conf_opt(&rsp, &type, &olen, &val); - if (len < 0) + int optlen = l2cap_get_conf_opt(&rsp, &type, &olen, &val, len); + + if (optlen < 0) break; + len -= optlen; switch (type) { case L2CAP_CONF_RFC: -- 2.53.0