diff options
| author | Weiming Shi <bestswngs@gmail.com> | 2026-06-03 01:06:21 +0800 |
|---|---|---|
| committer | Luiz Augusto von Dentz <luiz.von.dentz@intel.com> | 2026-06-11 14:24:40 -0400 |
| commit | 6f5fb689fdf80bdd143f22a502f9eb1f3c85e286 (patch) | |
| tree | 97c8f4860207667742c7d04d605e64596aecbd5a /net | |
| parent | ea77debfe443f505a4edbb7f21340a583a8a143f (diff) | |
Bluetooth: eir: Fix stack OOB write when prepending the Flags AD
eir_create_adv_data() builds the advertising data into a fixed-size
buffer ("size", 31 for the legacy path). It may prepend a 3-byte "Flags"
AD structure (LE_AD_NO_BREDR on an LE-only controller) and then copies
the per-instance data without checking that it still fits:
memcpy(ptr, adv->adv_data, adv->adv_data_len);
tlv_data_max_len() only reserves those 3 bytes when the user-supplied
flags carry a managed-flags bit, so an instance added with flags == 0 is
accepted with adv_data_len up to the full buffer. At advertise time the
flags are still prepended, and the memcpy() writes 3 + adv_data_len
bytes into the size-byte buffer:
BUG: KASAN: stack-out-of-bounds in eir_create_adv_data (net/bluetooth/eir.c:301)
Write of size 31 at addr ffff88800a547bdc by task kworker/u9:0/65
Workqueue: hci0 hci_cmd_sync_work
__asan_memcpy (mm/kasan/shadow.c:106)
eir_create_adv_data (net/bluetooth/eir.c:301)
hci_update_adv_data_sync (net/bluetooth/hci_sync.c:1310)
hci_schedule_adv_instance_sync (net/bluetooth/hci_sync.c:1817)
hci_cmd_sync_work (net/bluetooth/hci_sync.c:332)
This frame has 1 object:
[32, 64) 'cp'
The "Flags" structure is added by the kernel, not requested by
userspace, so only prepend it when it fits together with the instance
advertising data; when there is no room for both, drop the flags rather
than the user-provided data.
Reachable by a local user with CAP_NET_ADMIN owning an LE-only
controller on the legacy advertising path.
Fixes: b44133ff03be ("Bluetooth: Support the "discoverable" adv flag")
Reported-by: Xiang Mei <xmei5@asu.edu>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Diffstat (limited to 'net')
| -rw-r--r-- | net/bluetooth/eir.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/net/bluetooth/eir.c b/net/bluetooth/eir.c index 3f72111ba651..1de5f9df6eec 100644 --- a/net/bluetooth/eir.c +++ b/net/bluetooth/eir.c @@ -283,10 +283,12 @@ u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size) if (!flags) flags |= mgmt_get_adv_discov_flags(hdev); - /* If flags would still be empty, then there is no need to - * include the "Flags" AD field". + /* Only add the "Flags" if it fits together with the instance + * advertising data; drop it rather than overflow the buffer. */ - if (flags && (ad_len + eir_precalc_len(1) <= size)) { + if (flags && + (ad_len + eir_precalc_len(1) + + (adv ? adv->adv_data_len : 0) <= size)) { ptr[0] = 0x02; ptr[1] = EIR_FLAGS; ptr[2] = flags; |