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Tue, 19 May 2026 04:40:06 -0700 (PDT) Received: from localhost ([111.228.63.84]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2bd5d235e04sm188907075ad.80.2026.05.19.04.39.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2026 04:40:05 -0700 (PDT) From: Zhang Cen To: Marcel Holtmann , Luiz Augusto von Dentz Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, zerocling0077@gmail.com, 2045gemini@gmail.com, Zhang Cen Subject: [PATCH v3] Bluetooth: bnep: reject short frames before parsing Date: Tue, 19 May 2026 19:39:43 +0800 Message-Id: <20260519113943.3656062-1-rollkingzzc@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A BNEP peer can send a short BNEP SDU. bnep_rx_frame() reads the packet type byte immediately and, for control packets, reads the control opcode and setup UUID-size byte before proving that those bytes are present. bnep_rx_control() also dereferences the control opcode without rejecting an empty control payload. Use skb_pull_data() for the fixed fields in bnep_rx_frame() so a NULL return gates each dereference. Split the control handler so the frame path can pass an opcode that has already been pulled, and keep the byte-buffer wrapper for extension control payloads. KASAN report as below: BUG: KASAN: slab-out-of-bounds in bnep_rx_frame.isra.0+0x130c/0x1790 Read of size 1 at addr ffff88800c0f7909 The buggy address belongs to the object at ffff88800c0f7908 which belongs to the cache kmalloc-8 of size 8 The buggy address is located 0 bytes to the right of allocated 1-byte region [ffff88800c0f7908, ffff88800c0f7909) Call trace: dump_stack_lvl+0xb3/0x140 (?:?) print_address_description+0x57/0x3a0 (?:?) bnep_rx_frame+0x130c/0x1790 (net/bluetooth/bnep/core.c:306) print_report+0xb9/0x2b0 (?:?) __virt_addr_valid+0x1ba/0x3a0 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) kasan_addr_to_slab+0x21/0x60 (?:?) kasan_report+0xe0/0x110 (?:?) process_one_work+0xfce/0x17e0 (kernel/workqueue.c:3200) worker_thread+0x65c/0xe40 (?:?) __kthread_parkme+0x184/0x230 (?:?) kthread+0x35e/0x470 (?:?) _raw_spin_unlock_irq+0x28/0x50 (?:?) ret_from_fork+0x586/0x870 (?:?) __switch_to+0x74f/0xdc0 (?:?) ret_from_fork_asm+0x1a/0x30 (?:?) Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Zhang Cen --- v3: Use skb_pull_data() with NULL checks in bnep_rx_frame() instead of direct s= kb->len guards before fixed header dereferences. net/bluetooth/bnep/core.c | 51 ++++++++++++++++++++++++--------------- 1 file changed, 31 insertions(+), 20 deletions(-) diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c index 853c8d7644b55..de9c872e2c9cb 100644 --- a/net/bluetooth/bnep/core.c +++ b/net/bluetooth/bnep/core.c @@ -206,14 +206,11 @@ static int bnep_ctrl_set_mcfilter(struct bnep_session= *s, u8 *data, int len) return 0; } =20 -static int bnep_rx_control(struct bnep_session *s, void *data, int len) +static int bnep_rx_control_cmd(struct bnep_session *s, u8 cmd, void *data, + int len) { - u8 cmd =3D *(u8 *)data; int err =3D 0; =20 - data++; - len--; - switch (cmd) { case BNEP_CMD_NOT_UNDERSTOOD: case BNEP_SETUP_CONN_RSP: @@ -254,6 +251,14 @@ static int bnep_rx_control(struct bnep_session *s, voi= d *data, int len) return err; } =20 +static int bnep_rx_control(struct bnep_session *s, void *data, int len) +{ + if (len < 1) + return -EILSEQ; + + return bnep_rx_control_cmd(s, *(u8 *)data, data + 1, len - 1); +} + static int bnep_rx_extension(struct bnep_session *s, struct sk_buff *skb) { struct bnep_ext_hdr *h; @@ -299,19 +304,26 @@ static int bnep_rx_frame(struct bnep_session *s, stru= ct sk_buff *skb) { struct net_device *dev =3D s->dev; struct sk_buff *nskb; + u8 *data; u8 type, ctrl_type; =20 dev->stats.rx_bytes +=3D skb->len; =20 - type =3D *(u8 *) skb->data; - skb_pull(skb, 1); - ctrl_type =3D *(u8 *)skb->data; + data =3D skb_pull_data(skb, sizeof(type)); + if (!data) + goto badframe; + type =3D *data; =20 if ((type & BNEP_TYPE_MASK) >=3D sizeof(__bnep_rx_hlen)) goto badframe; =20 if ((type & BNEP_TYPE_MASK) =3D=3D BNEP_CONTROL) { - if (bnep_rx_control(s, skb->data, skb->len) < 0) { + data =3D skb_pull_data(skb, sizeof(ctrl_type)); + if (!data) + goto badframe; + ctrl_type =3D *data; + + if (bnep_rx_control_cmd(s, ctrl_type, skb->data, skb->len) < 0) { dev->stats.tx_errors++; kfree_skb(skb); return 0; @@ -325,23 +337,22 @@ static int bnep_rx_frame(struct bnep_session *s, stru= ct sk_buff *skb) /* Verify and pull ctrl message since it's already processed */ switch (ctrl_type) { case BNEP_SETUP_CONN_REQ: - /* Pull: ctrl type (1 b), len (1 b), data (len bytes) */ - if (!skb_pull(skb, 2 + *(u8 *)(skb->data + 1) * 2)) + /* Pull: len (1 b), data (len * 2 bytes) */ + data =3D skb_pull_data(skb, 1); + if (!data) + goto badframe; + if (!skb_pull(skb, *data * 2)) goto badframe; break; case BNEP_FILTER_MULTI_ADDR_SET: - case BNEP_FILTER_NET_TYPE_SET: { - u8 *hdr; - - /* Pull ctrl type (1 b) + len (2 b) */ - hdr =3D skb_pull_data(skb, 3); - if (!hdr) + case BNEP_FILTER_NET_TYPE_SET: + /* Pull: len (2 b), data (len bytes) */ + data =3D skb_pull_data(skb, sizeof(u16)); + if (!data) goto badframe; - /* Pull data (len bytes); length is big-endian */ - if (!skb_pull(skb, get_unaligned_be16(&hdr[1]))) + if (!skb_pull(skb, get_unaligned_be16(data))) goto badframe; break; - } default: kfree_skb(skb); return 0; --=20 2.43.0