[PATCH v5] Bluetooth: bnep: reject short frames before parsing

[PATCH v5] Bluetooth: bnep: reject short frames before parsing

[Zhang Cen]

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.

For BNEP_SETUP_CONN_REQ, name the UUID-size byte before pulling the
setup payload. struct bnep_setup_conn_req carries destination and source
service UUIDs after that byte, each uuid_size bytes, so the parser now
documents that tuple explicitly instead of leaving the pull length as an
opaque multiplication.

Validation reproduced this kernel report:
KASAN slab-out-of-bounds in bnep_rx_frame.isra.0+0x130c/0x1790
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)
Read of size 1
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")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Zhang Cen <rollkingzzc@gmail.com>
---
v5:
Clarify the BNEP_SETUP_CONN_REQ UUID-size handling using the setup
request layout from struct bnep_setup_conn_req.

v4:
Wrap the changelog entry that Bluetooth CI flagged as overlong.
Keep the BNEP code fix unchanged from the last submitted patch.

v3:
Use skb_pull_data() with NULL checks in bnep_rx_frame() instead of direct
skb->len guards before fixed header dereferences.
Split control handling so bnep_rx_frame() can pass an already pulled control
opcode while preserving the existing extension control wrapper.

 net/bluetooth/bnep/core.c | 57 ++++++++++++++++++++++++---------------
 1 file changed, 36 insertions(+), 21 deletions(-)

diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index 0de5df690bd0..5c5f53ff30e8 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;
 }
 
-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 = *(u8 *)data;
 	int err = 0;
 
-	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, void *data, int len)
 	return err;
 }
 
+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, struct sk_buff *skb)
 {
 	struct net_device *dev = s->dev;
 	struct sk_buff *nskb;
+	u8 *data;
 	u8 type, ctrl_type;
 
 	dev->stats.rx_bytes += skb->len;
 
-	type = *(u8 *) skb->data;
-	skb_pull(skb, 1);
-	ctrl_type = *(u8 *)skb->data;
+	data = skb_pull_data(skb, sizeof(type));
+	if (!data)
+		goto badframe;
+	type = *data;
 
 	if ((type & BNEP_TYPE_MASK) >= sizeof(__bnep_rx_hlen))
 		goto badframe;
 
 	if ((type & BNEP_TYPE_MASK) == BNEP_CONTROL) {
-		if (bnep_rx_control(s, skb->data, skb->len) < 0) {
+		data = skb_pull_data(skb, sizeof(ctrl_type));
+		if (!data)
+			goto badframe;
+		ctrl_type = *data;
+
+		if (bnep_rx_control_cmd(s, ctrl_type, skb->data, skb->len) < 0) {
 			dev->stats.tx_errors++;
 			kfree_skb(skb);
 			return 0;
@@ -324,24 +336,27 @@ static int bnep_rx_frame(struct bnep_session *s, struct 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))
+		case BNEP_SETUP_CONN_REQ: {
+			u8 uuid_size;
+
+			/* Pull uuid_size and the dst/src service UUIDs. */
+			data = skb_pull_data(skb, sizeof(uuid_size));
+			if (!data)
+				goto badframe;
+			uuid_size = *data;
+			if (!skb_pull(skb, uuid_size + uuid_size))
 				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 = skb_pull_data(skb, 3);
-			if (!hdr)
+		case BNEP_FILTER_NET_TYPE_SET:
+			/* Pull: len (2 b), data (len bytes) */
+			data = 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;
-- 
2.43.0

RE: [v5] Bluetooth: bnep: reject short frames before parsing

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 1042 bytes --]

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=1102596

---Test result---

Test Summary:
CheckPatch                    PASS      0.78 seconds
VerifyFixes                   PASS      0.14 seconds
VerifySignedoff               PASS      0.14 seconds
GitLint                       PASS      0.34 seconds
SubjectPrefix                 PASS      0.13 seconds
BuildKernel                   PASS      25.21 seconds
CheckAllWarning               PASS      27.81 seconds
CheckSparse                   PASS      26.46 seconds
BuildKernel32                 PASS      24.59 seconds
TestRunnerSetup               PASS      530.02 seconds
TestRunner_bnep-tester        PASS      19.02 seconds
IncrementalBuild              PASS      24.35 seconds



https://github.com/bluez/bluetooth-next/pull/253

---
Regards,
Linux Bluetooth

Re: [PATCH v5] Bluetooth: bnep: reject short frames before parsing

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Fri, 29 May 2026 11:22:09 +0800 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [v5] Bluetooth: bnep: reject short frames before parsing
    https://git.kernel.org/bluetooth/bluetooth-next/c/379b101059b4

You are awesome, thank you!
-- 
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