* [PATCH v3] Bluetooth: MGMT: Fix mesh_tx Use-After-Free and leak in mesh_send()
[not found] <20260919080846.3005471-1-benquike@gmail.com>
@ 2026-09-19 11:25 ` Hui Peng
2026-09-19 11:55 ` Hui Peng
0 siblings, 1 reply; 2+ messages in thread
From: Hui Peng @ 2026-09-19 11:25 UTC (permalink / raw)
To: marcel, luiz.dentz; +Cc: linux-bluetooth, linux-kernel
In mesh_send(), a struct mgmt_mesh_tx entry is allocated and added to
hdev->mesh_pending via mgmt_mesh_add(sk, hdev, send, len) before queuing
mesh_send_sync() and mesh_send_start_complete() onto hdev->req_workqueue
with mesh_tx as the callback data pointer.
Before or while the workqueue executes mesh_send_sync() and
mesh_send_start_complete(), mesh_tx can be removed from
hdev->mesh_pending and freed via mgmt_mesh_remove():
1. If an earlier MGMT_OP_MESH_SEND_CANCEL (send_cancel()) item runs on
hdev->req_workqueue, send_cancel() calls mesh_send_complete(), which
removes and frees mesh_tx.
2. If the management socket is closed, mgmt_cleanup() removes and frees
all mesh_tx entries matching sk under hci_dev_lock(hdev).
When mesh_send_sync() and mesh_send_start_complete() subsequently run,
they dereference the dangling mesh_tx pointer (mesh_tx->param,
mesh_tx->handle, mesh_tx->instance), and mesh_send_start_complete()
frees mesh_tx a second time via mesh_send_complete() on error.
Furthermore, if hci_cmd_sync_queue() fails in mesh_send() (which can
only happen in the !sending branch), mesh_send() only called
mgmt_mesh_remove(mesh_tx) when if (sending) was true (an inverted
condition), leaking mesh_tx on hdev->mesh_pending.
Fix this by holding hci_dev_lock(hdev) and verifying
mesh_tx == mgmt_mesh_next(hdev, NULL) across all mesh_tx and send
dereferences in mesh_send_sync() and mesh_send_start_complete(), and
unconditionally calling mgmt_mesh_remove(mesh_tx) on
hci_cmd_sync_queue() error in mesh_send().
Kernel stack trace (Linux 7.3.0-rc3):
==================================================================
BUG: KASAN: slab-use-after-free in mesh_send_sync+0x39a/0x410
Read of size 1 at addr ffff8880132fe53b by task kworker/u9:1/143
CPU: 1 UID: 0 PID: 143 Comm: kworker/u9:1 Not tainted 7.3.0-rc3-g5dd1818b15d9 #1 PREEMPT(lazy)
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
<TASK>
dump_stack_lvl+0x70/0xa0
print_report+0x153/0x4c6
kasan_report+0xf1/0x120
mesh_send_sync+0x39a/0x410
hci_cmd_sync_work+0x14e/0x2a0
process_one_work+0x6ff/0x1110
worker_thread+0x4a8/0xb70
kthread+0x307/0x3e0
ret_from_fork+0x3ed/0x680
ret_from_fork_asm+0x1a/0x30
</TASK>
Allocated by task 1:
kasan_save_stack+0x30/0x50
kasan_save_track+0x14/0x30
__kasan_kmalloc+0x7f/0x90
__kmalloc_cache_noprof+0x16a/0x380
mgmt_mesh_add+0x5b/0x340
mesh_send+0x22b/0x690
hci_sock_sendmsg+0x1155/0x2040
sock_write_iter+0x492/0x520
vfs_write+0x671/0xd20
ksys_write+0x1bb/0x210
do_syscall_64+0xda/0x4b0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 143:
kasan_save_stack+0x30/0x50
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x70
__kasan_slab_free+0x47/0x70
kfree+0x159/0x420
send_cancel+0x14e/0x360
hci_cmd_sync_work+0x14e/0x2a0
process_one_work+0x6ff/0x1110
worker_thread+0x4a8/0xb70
kthread+0x307/0x3e0
ret_from_fork+0x3ed/0x680
ret_from_fork_asm+0x1a/0x30
The buggy address belongs to the object at 0xffff8880132fe500
which belongs to the cache kmalloc-96 of size 96
The buggy address is located 59 bytes inside of
freed 96-byte region [ffff8880132fe500, ffff8880132fe560)
==================================================================
Fixes: b338d91703fa ("Bluetooth: Implement support for Mesh")
Assisted-by: LLM
Signed-off-by: Hui Peng <benquike@gmail.com>
---
v3: Add a Fixes: tag. The allocator (mgmt_mesh_add() in mesh_send()),
the freeing path (mesh_send_complete() from send_cancel()), the racing
dereference (mesh_send_sync()), the unlocked hci_add_adv_instance()
call and the missing mgmt_mesh_remove() on the !sending path all came
in together with b338d91703fa ("Bluetooth: Implement support for
Mesh"), first released in v6.1. No later commit touched any of the
lines this patch changes.
This patch fixes two things that share that one origin: the
UAF/locking race, and the leak when the send is not queued. Happy to
split it into two patches if you prefer - both halves would carry the
same tag.
Backporting: the hunks apply back to v6.1, but mesh_send() picked up
extra validation in bda93eec78cd, so older stable branches may need a
trivial context fixup.
v2: Resend via git send-email with intact tab formatting and Assisted-by: LLM tag.
Reproducer (triggers KASAN slab-use-after-free in mesh_send_sync() on
Linux 7.3.0-rc3 via /dev/vhci and MGMT_OP_MESH_SEND_CANCEL +
MGMT_OP_MESH_SEND):
/* 1. Enable Mesh experimental feature (UUID 766ef3e8-245f-05bf-8d4d-037ad763e42c)
* and LE on hci0 via MGMT_OP_SET_EXP_FEATURE (0x004a) and MGMT_OP_SET_LE (0x000d).
* 2. Hold hdev->req_workqueue briefly in set_name_sync (MGMT_OP_SET_LOCAL_NAME 0x000f).
* 3. Queue MGMT_OP_MESH_SEND_CANCEL (0x005a, handle = 0) followed immediately by
* MGMT_OP_MESH_SEND (0x0059) on a second MGMT control socket.
* 4. MGMT_OP_MESH_SEND synchronously adds mesh_tx to hdev->mesh_pending (assigning
* handle = 1, or matching handle = 0 cancel) and queues mesh_send_sync(mesh_tx).
* When send_cancel() runs first on hdev->req_workqueue, it frees mesh_tx, and
* mesh_send_sync() immediately dereferences the freed mesh_tx. */
net/bluetooth/mgmt.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index ac4864e56..fbf85e791 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -2306,36 +2306,53 @@ static int set_mesh(struct sock *sk, struct hci_dev *hdev, void *data, u16 len)
static void mesh_send_start_complete(struct hci_dev *hdev, void *data, int err)
{
struct mgmt_mesh_tx *mesh_tx = data;
- struct mgmt_cp_mesh_send *send = (void *)mesh_tx->param;
+ struct mgmt_cp_mesh_send *send;
unsigned long mesh_send_interval;
u8 mgmt_err = mgmt_status(err);
- /* Report any errors here, but don't report completion */
+ hci_dev_lock(hdev);
+ if (mesh_tx != mgmt_mesh_next(hdev, NULL)) {
+ hci_dev_unlock(hdev);
+ return;
+ }
+ /* Report any errors here, but don't report completion */
if (mgmt_err) {
hci_dev_clear_flag(hdev, HCI_MESH_SENDING);
/* Send Complete Error Code for handle */
mesh_send_complete(hdev, mesh_tx, false);
+ hci_dev_unlock(hdev);
return;
}
+ send = (void *)mesh_tx->param;
mesh_send_interval = msecs_to_jiffies((send->cnt) * 25);
queue_delayed_work(hdev->req_workqueue, &hdev->mesh_send_done,
mesh_send_interval);
+ hci_dev_unlock(hdev);
}
static int mesh_send_sync(struct hci_dev *hdev, void *data)
{
struct mgmt_mesh_tx *mesh_tx = data;
- struct mgmt_cp_mesh_send *send = (void *)mesh_tx->param;
+ struct mgmt_cp_mesh_send *send;
struct adv_info *adv, *next_instance;
u8 instance = hdev->le_num_of_adv_sets + 1;
u16 timeout, duration;
int err = 0;
- if (hdev->le_num_of_adv_sets <= hdev->adv_instance_cnt)
+ hci_dev_lock(hdev);
+ if (mesh_tx != mgmt_mesh_next(hdev, NULL)) {
+ hci_dev_unlock(hdev);
+ return MGMT_STATUS_FAILED;
+ }
+
+ if (hdev->le_num_of_adv_sets <= hdev->adv_instance_cnt) {
+ hci_dev_unlock(hdev);
return MGMT_STATUS_BUSY;
+ }
+ send = (void *)mesh_tx->param;
timeout = 1000;
duration = send->cnt * INTERVAL_TO_MS(hdev->le_adv_max_interval);
adv = hci_add_adv_instance(hdev, instance, 0,
@@ -2372,6 +2389,8 @@ static int mesh_send_sync(struct hci_dev *hdev, void *data)
instance = 0;
}
+ hci_dev_unlock(hdev);
+
if (instance)
return hci_schedule_adv_instance_sync(hdev, instance, true);
@@ -2534,10 +2553,8 @@ static int mesh_send(struct sock *sk, struct hci_dev *hdev, void *data, u16 len)
err = mgmt_cmd_status(sk, hdev->id, MGMT_OP_MESH_SEND,
MGMT_STATUS_FAILED);
- if (mesh_tx) {
- if (sending)
- mgmt_mesh_remove(mesh_tx);
- }
+ if (mesh_tx)
+ mgmt_mesh_remove(mesh_tx);
} else {
hci_dev_set_flag(hdev, HCI_MESH_SENDING);
--
2.43.0
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