staging: rtl8723bs: fix OOB read in rtw_action_frame_parse()grafted

rtw_action_frame_parse() takes a frame_len parameter but never
actually checks it before indexing into the frame body:

	const u8 *frame_body = frame + sizeof(struct ieee80211_hdr_3addr);
	...
	c = frame_body[0];
	...
	a = frame_body[1];

frame_body already points 24 bytes (sizeof(struct
ieee80211_hdr_3addr)) into frame, so reading frame_body[0] and
frame_body[1] requires frame_len >= 26. A management action frame
shorter than that (e.g. exactly 24 bytes, the minimum a malicious
peer can send) causes a 1-2 byte out-of-bounds read.

This is reachable from rtw_cfg80211_monitor_if_xmit_entry() and
cfg80211_rtw_mgmt_tx() in ioctl_cfg80211.c, both of which pass
attacker/user-influenced frame buffers and lengths straight through.

Add the missing length check before frame_body is dereferenced.

Fixes: 554c0a3abf216 ("staging: Add rtl8723bs sdio wifi driver")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
Link: https://patch.msgid.link/20260728125456.32359-3-meatuni001@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/lib/memweight.c b/lib/memweight.c
new file mode 100644
index 000000000..94dd72cca
--- /dev/null
+++ b/lib/memweight.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/export.h>
+#include <linux/bug.h>
+#include <linux/bitmap.h>
+
+/**
+ * memweight - count the total number of bits set in memory area
+ * @ptr: pointer to the start of the area
+ * @bytes: the size of the area
+ */
+size_t memweight(const void *ptr, size_t bytes)
+{
+	size_t ret = 0;
+	size_t longs;
+	const unsigned char *bitmap = ptr;
+
+	for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long);
+			bytes--, bitmap++)
+		ret += hweight8(*bitmap);
+
+	longs = bytes / sizeof(long);
+	if (longs) {
+		BUG_ON(longs >= INT_MAX / BITS_PER_LONG);
+		ret += bitmap_weight((unsigned long *)bitmap,
+				longs * BITS_PER_LONG);
+		bytes -= longs * sizeof(long);
+		bitmap += longs * sizeof(long);
+	}
+	/*
+	 * The reason that this last loop is distinct from the preceding
+	 * bitmap_weight() call is to compute 1-bits in the last region smaller
+	 * than sizeof(long) properly on big-endian systems.
+	 */
+	for (; bytes > 0; bytes--, bitmap++)
+		ret += hweight8(*bitmap);
+
+	return ret;
+}
+EXPORT_SYMBOL(memweight);