[PATCH 4/5] staging: rtl8723bs: fix OOB read in rtw_restruct_wmm_ie()

[Muhammad Bilal <meatuni001@gmail.com>]

rtw_restruct_wmm_ie() scans in_ie for a WMM IE with:

	while (i < in_len) {
		...
		if (i + 5 < in_len && in_ie[i] == 0xDD && ...) {
			...
			break;
		}
		i += (in_ie[i + 1] + 2); /* to the next IE element */
	}

When the "i + 5 < in_len" match check fails simply because i is
within 5 bytes of the end of the buffer (i.e. no WMM IE was found
near the tail of in_ie), execution falls through to
"i += (in_ie[i + 1] + 2)", which reads in_ie[i + 1]. If i == in_len
- 1 at that point, this is a 1-byte out-of-bounds read of an
attacker-influenced IE buffer built from association/scan data.

Commit a75281626fc8f ("staging: rtl8723bs: fix potential
out-of-bounds read in rtw_restruct_wmm_ie") added the "i + 5 <
in_len" guard to the match condition itself, but did not add an
equivalent guard before the fallthrough advance, so the same class
of OOB read remained reachable through the non-matching path.

Add an explicit bounds check before advancing to the next IE.

Fixes: 554c0a3abf216 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 drivers/staging/rtl8723bs/core/rtw_mlme.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/rtl8723bs/core/rtw_mlme.c b/drivers/staging/rtl8723bs/core/rtw_mlme.c
index 1196ec011455..7bdc5fe6dc8a 100644
--- a/drivers/staging/rtl8723bs/core/rtw_mlme.c
+++ b/drivers/staging/rtl8723bs/core/rtw_mlme.c
@@ -1980,6 +1980,9 @@ int rtw_restruct_wmm_ie(struct adapter *adapter, u8 *in_ie, u8 *out_ie, uint in_
 			break;
 		}
 
+		if (i + 1 >= in_len)
+			break;
+
 		i += (in_ie[i + 1] + 2); /*  to the next IE element */
 	}
 
-- 
2.55.0