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

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

[Zhang Cen]

An L2CAP peer can deliver an empty BNEP payload or a payload that contains
only the outer type byte. bnep_rx_frame() currently dereferences the type
byte and, for control traffic, the control opcode before it proves that
those bytes exist in the skb. The setup-connection control path can also
read the setup size byte before it is present. bnep_rx_control() has the
same problem when it is asked to parse an empty control payload.

Reject empty skbs before reading the outer type byte, require a control
opcode before parsing BNEP_CONTROL, require the setup size byte before
using it, and make bnep_rx_control() fail zero-length control payloads.

Sanitizer validation reported:
KASAN slab-out-of-bounds in bnep_rx_frame()
Read of size 1
Call trace:
  dump_stack_lvl() (?:?)
  print_address_description() (mm/kasan/report.c:373)
  bnep_rx_frame() (net/bluetooth/bnep/core.c:306)
  print_report() (?:?)
  __virt_addr_valid() (?:?)
  srso_alias_return_thunk() (arch/x86/include/asm/nospec-branch.h:375)
  kasan_addr_to_slab() (mm/kasan/common.c:45)
  kasan_report() (?:?)
  process_one_work() (kernel/workqueue.c:3200)
  worker_thread() (?:?)
  __kthread_parkme() (kernel/kthread.c:259)
  kthread() (?:?)
  _raw_spin_unlock_irq() (kernel/locking/spinlock.c:204)
  ret_from_fork() (?:?)
  __switch_to() (?:?)
  ret_from_fork_asm() (?:?)
  kasan_save_stack() (mm/kasan/common.c:52)
  kasan_save_track() (mm/kasan/common.c:74)
  __kasan_kmalloc() (?:?)
  vpanic() (kernel/panic.c:576)
  panic() (?:?)
  preempt_schedule_common() (kernel/sched/core.c:7352)
  preempt_schedule_thunk() (?:?)
  end_report() (mm/kasan/report.c:219)

Signed-off-by: Zhang Cen <rollkingzzc@gmail.com>

---
diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index d44987d4515c..f5070bbd6b57 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -208,9 +208,14 @@ static int bnep_ctrl_set_mcfilter(struct bnep_session *s, u8 *data, int len)
 
 static int bnep_rx_control(struct bnep_session *s, void *data, int len)
 {
-	u8  cmd = *(u8 *)data;
+	u8  cmd;
 	int err = 0;
 
+	if (len < 1)
+		return -EILSEQ;
+
+	cmd = *(u8 *)data;
+
 	data++;
 	len--;
 
@@ -303,14 +308,21 @@ static int bnep_rx_frame(struct bnep_session *s, struct sk_buff *skb)
 
 	dev->stats.rx_bytes += skb->len;
 
+	if (skb->len < 1)
+		goto badframe;
+
 	type = *(u8 *) skb->data;
 	skb_pull(skb, 1);
-	ctrl_type = *(u8 *)skb->data;
 
 	if ((type & BNEP_TYPE_MASK) >= sizeof(__bnep_rx_hlen))
 		goto badframe;
 
 	if ((type & BNEP_TYPE_MASK) == BNEP_CONTROL) {
+		if (skb->len < 1)
+			goto badframe;
+
+		ctrl_type = *(u8 *)skb->data;
+
 		if (bnep_rx_control(s, skb->data, skb->len) < 0) {
 			dev->stats.tx_errors++;
 			kfree_skb(skb);
@@ -326,6 +338,9 @@ static int bnep_rx_frame(struct bnep_session *s, struct sk_buff *skb)
 		switch (ctrl_type) {
 		case BNEP_SETUP_CONN_REQ:
 			/* Pull: ctrl type (1 b), len (1 b), data (len bytes) */
+			if (skb->len < 2)
+				goto badframe;
+
 			if (!skb_pull(skb, 2 + *(u8 *)(skb->data + 1) * 2))
 				goto badframe;
 			break;

RE: Bluetooth: bnep: reject short frames before parsing

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 936 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=1093891

---Test result---

Test Summary:
CheckPatch                    PASS      0.71 seconds
GitLint                       PASS      0.29 seconds
SubjectPrefix                 PASS      0.11 seconds
BuildKernel                   PASS      26.69 seconds
CheckAllWarning               PASS      29.05 seconds
CheckSparse                   PASS      27.92 seconds
BuildKernel32                 PASS      25.69 seconds
TestRunnerSetup               PASS      568.44 seconds
TestRunner_bnep-tester        PASS      18.92 seconds
IncrementalBuild              PASS      25.28 seconds



https://github.com/bluez/bluetooth-next/pull/181

---
Regards,
Linux Bluetooth