[PATCH bluetooth] Bluetooth: qca: fix NVM tag length underflow in TLV parser

[Xiang Mei <xmei5@asu.edu>]

In the TLV_TYPE_NVM branch of qca_tlv_check_data() the tag loop bound is
"while (idx < length - sizeof(struct tlv_type_nvm))". "length" is a signed
int from the firmware TLV header and sizeof(struct tlv_type_nvm) is a
size_t (12), so "length" is converted to size_t and any firmware-supplied
"length" < 12 makes the subtraction wrap to a huge value. The loop body
then reads a 12-byte struct tlv_type_nvm past the end of the short
vmalloc'd firmware buffer (and the EDL_TAG_ID_* handlers can write past it).

Rewrite the bound as "idx + sizeof(struct tlv_type_nvm) <= length"; both
operands are non-negative, so it no longer underflows and a "length" too
small for one record correctly skips the loop.

  BUG: KASAN: vmalloc-out-of-bounds in qca_download_firmware.isra.0 (drivers/bluetooth/btqca.c:421)
  Read of size 2 at addr ffffc900000e5004 by task kworker/u9:0/52
  Workqueue: hci0 hci_power_on
  Call Trace:
   ...
   kasan_report (mm/kasan/report.c:595)
   qca_download_firmware.isra.0 (drivers/bluetooth/btqca.c:421 drivers/bluetooth/btqca.c:617)
   qca_uart_setup (drivers/bluetooth/btqca.c:948)
   qca_setup (drivers/bluetooth/hci_qca.c:2029)
   hci_uart_setup (drivers/bluetooth/hci_ldisc.c:438)
   hci_dev_open_sync (net/bluetooth/hci_sync.c:5227)
   hci_power_on (net/bluetooth/hci_core.c:920)
   process_one_work (kernel/workqueue.c:3322)
   worker_thread (kernel/workqueue.c:3486)
   kthread (kernel/kthread.c:436)
   ret_from_fork (arch/x86/kernel/process.c:158)
   ret_from_fork_asm (arch/x86/entry/entry_64.S:245)

Fixes: 2e4edfa1e2bd ("Bluetooth: qca: add missing firmware sanity checks")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
---
 drivers/bluetooth/btqca.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btqca.c b/drivers/bluetooth/btqca.c
index 04ebe290bc78..10c496eaea2c 100644
--- a/drivers/bluetooth/btqca.c
+++ b/drivers/bluetooth/btqca.c
@@ -415,7 +415,7 @@ static int qca_tlv_check_data(struct hci_dev *hdev,
 
 		idx = 0;
 		data = tlv->data;
-		while (idx < length - sizeof(struct tlv_type_nvm)) {
+		while (idx + sizeof(struct tlv_type_nvm) <= length) {
 			tlv_nvm = (struct tlv_type_nvm *)(data + idx);
 
 			tag_id = le16_to_cpu(tlv_nvm->tag_id);
-- 
2.43.0