[PATCH v3] wifi: mwifiex: bound the pairwise-cipher OUI walk to the IE length

[Doruk Tan Ozturk <doruk@0sec.ai>]

mwifiex_search_oui_in_ie() reads a pairwise-cipher (PTK) count from a
beacon/probe-response RSN or WPA information element and then walks that
many 4-byte OUIs, comparing each with memcmp(). The count comes straight
from the (attacker-supplied) IE and is never checked against the
element's own length, and the callers admit the element on element_id
alone (has_ieee_hdr() / has_vendor_hdr(), no length check). A crafted
RSN/WPA IE with a large pairwise count therefore makes the walk read up
to 255 * 4 bytes past the element -- an out-of-bounds read of the
kmemdup()'d beacon buffer, reachable from any AP whose beacon/probe
response is processed during scan-result parsing.

Pass the number of IE bytes available at the OUI list and bound the walk
to the element. Keep the length signed and reject a negative value
before any unsigned arithmetic, so a small or zero IE length cannot
underflow to a large size_t and defeat the bound.

Found by 0sec automated security-research tooling (https://0sec.ai).

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Cc: stable@vger.kernel.org
Assisted-by: 0sec:multi-model
Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>
---

Changes in v3 (per Brian Norris's review of v2):
 - Keep ie_len signed and explicitly reject a negative (underflowed)
   length before any unsigned arithmetic. The v2 bound added the count
   to the offset and compared against (size_t)ie_len, so a small or zero
   IE length that underflowed ie_len wrapped to a large size_t and the
   bound would not fire.

Changes in v2 (per Francesco Dolcini's review of v1):
 - Store offsetof(struct ie_body, ptk_body) in a named variable
   (ptk_body_offset) and reuse it in both bounds checks; no functional
   change.
 - Switch the Assisted-by trailer to 0sec:multi-model.

 drivers/net/wireless/marvell/mwifiex/scan.c | 25 ++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
index 97c0ec3b822e7..473f4623ea199 100644
--- a/drivers/net/wireless/marvell/mwifiex/scan.c
+++ b/drivers/net/wireless/marvell/mwifiex/scan.c
@@ -104,12 +104,24 @@ has_vendor_hdr(struct ieee_types_vendor_specific *ie, u8 key)
  * a given oui in PTK.
  */
 static u8
-mwifiex_search_oui_in_ie(struct ie_body *iebody, u8 *oui)
+mwifiex_search_oui_in_ie(struct ie_body *iebody, u8 *oui, int ie_len)
 {
+	const size_t ptk_body_offset = offsetof(struct ie_body, ptk_body);
 	u8 count;
 
+	/* ie_len is the number of bytes available at iebody. Keep it signed
+	 * and reject a negative (underflowed) length before the unsigned
+	 * comparisons below, so a small or zero IE length cannot wrap.
+	 */
+	if (ie_len < 0 || (size_t)ie_len < ptk_body_offset)
+		return MWIFIEX_OUI_NOT_PRESENT;
+
 	count = iebody->ptk_cnt[0];
 
+	/* Reject an OUI count whose list would run past the element. */
+	if (ptk_body_offset + count * sizeof(iebody->ptk_body) > (size_t)ie_len)
+		return MWIFIEX_OUI_NOT_PRESENT;
+
 	/* There could be multiple OUIs for PTK hence
 	   1) Take the length.
 	   2) Check all the OUIs for AES.
@@ -143,11 +155,14 @@ mwifiex_is_rsn_oui_present(struct mwifiex_bssdescriptor *bss_desc, u32 cipher)
 	u8 ret = MWIFIEX_OUI_NOT_PRESENT;
 
 	if (has_ieee_hdr(bss_desc->bcn_rsn_ie, WLAN_EID_RSN)) {
+		int ie_len = (int)bss_desc->bcn_rsn_ie->ieee_hdr.len -
+			RSN_GTK_OUI_OFFSET;
+
 		iebody = (struct ie_body *)
 			 (((u8 *) bss_desc->bcn_rsn_ie->data) +
 			  RSN_GTK_OUI_OFFSET);
 		oui = &mwifiex_rsn_oui[cipher][0];
-		ret = mwifiex_search_oui_in_ie(iebody, oui);
+		ret = mwifiex_search_oui_in_ie(iebody, oui, ie_len);
 		if (ret)
 			return ret;
 	}
@@ -169,10 +184,14 @@ mwifiex_is_wpa_oui_present(struct mwifiex_bssdescriptor *bss_desc, u32 cipher)
 	u8 ret = MWIFIEX_OUI_NOT_PRESENT;
 
 	if (has_vendor_hdr(bss_desc->bcn_wpa_ie, WLAN_EID_VENDOR_SPECIFIC)) {
+		int ie_len = (int)bss_desc->bcn_wpa_ie->vend_hdr.len -
+			(int)sizeof(bss_desc->bcn_wpa_ie->vend_hdr.oui) -
+			WPA_GTK_OUI_OFFSET;
+
 		iebody = (struct ie_body *)((u8 *)bss_desc->bcn_wpa_ie->data +
 					    WPA_GTK_OUI_OFFSET);
 		oui = &mwifiex_wpa_oui[cipher][0];
-		ret = mwifiex_search_oui_in_ie(iebody, oui);
+		ret = mwifiex_search_oui_in_ie(iebody, oui, ie_len);
 		if (ret)
 			return ret;
 	}
-- 
2.43.0