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Tue, 05 May 2026 10:38:26 -0700 (PDT) From: Alexandru Hossu To: gregkh@linuxfoundation.org Cc: linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, error27@gmail.com, luka.gejak@linux.dev, stable@vger.kernel.org Subject: [PATCH v4 1/3] staging: rtl8723bs: fix OOB reads in update_beacon_info() and bwmode_update_check() Date: Tue, 5 May 2026 19:38:16 +0200 Message-ID: <20260505173818.3674164-2-hossu.alexandru@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260505173818.3674164-1-hossu.alexandru@gmail.com> References: <2026050436-italics-clumsy-e83c@gregkh> <20260505173818.3674164-1-hossu.alexandru@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Four out-of-bounds read paths in Beacon IE processing: 1. Unsigned underflow in len computation. update_beacon_info() computes: len = pkt_len - (_BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN); where len is unsigned int. If pkt_len is smaller than _BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN (36 bytes), the subtraction wraps to a very large value, causing the IE loop to iterate over memory far beyond the receive buffer. Add an early return when pkt_len is too small. 2. IE header and payload may extend past the packet end. The IE loop advances by pIE->length + 2 per iteration but only guards on i < len. When the last IE has only one byte left in the frame, the loop reads pIE->length from pframe[len], one byte past the receive buffer. Even when the header bytes are in bounds, pIE->length can point the data window past len, silently passing a truncated IE to handler functions. Add two guards: break if fewer than sizeof(*pIE) bytes remain, and break if the declared IE payload extends past len. 3. WMM OUI comparison reads 6 bytes past a possibly short IE payload. For WLAN_EID_VENDOR_SPECIFIC, the code calls memcmp(pIE->data, WMM_PARA_OUI, 6) before checking pIE->length == WLAN_WMM_LEN. An IE with pIE->length < 6 causes memcmp to read into adjacent frame data. Swap the condition so the length check comes first. 4. bwmode_update_check() missing minimum IE length check. bwmode_update_check() rejects IEs longer than sizeof(struct HT_info_element) but accepts any shorter length, including zero. After the check it casts pIE->data to struct HT_info_element * and reads infos[0] (offset 1), which is out of bounds when pIE->length is 0 or 1. Change the guard from > to != to require the IE to be exactly the expected size. Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver") Cc: stable@vger.kernel.org Signed-off-by: Alexandru Hossu --- Changes in v4: - Add pkt_len < _BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN guard before the len subtraction to prevent unsigned underflow (sashiko review of v3). - Swap WLAN_EID_VENDOR_SPECIFIC condition: check pIE->length == WLAN_WMM_LEN before memcmp to avoid reading 6 bytes from a short IE payload (sashiko review of v3). - Fix bwmode_update_check(): change > sizeof(struct HT_info_element) to != sizeof(struct HT_info_element) to also reject IEs shorter than the expected size, preventing the read of infos[0] on a zero-length IE (sashiko review of v3). Changes in v3: - No code changes from v2. Changes in v2: - Add IE loop header and payload bounds checks in update_beacon_info(). - Use sizeof(*pIE) + pIE->length instead of pIE->length + 2 for consistency with the sizeof(*pIE) guards (Dan Carpenter). drivers/staging/rtl8723bs/core/rtw_wlan_util.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c index 6a7c09db4cd9..7ccfaa538ebb 100644 --- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c +++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c @@ -850,7 +850,7 @@ static void bwmode_update_check(struct adapter *padapter, struct ndis_80211_var_ if (phtpriv->ht_option == false) return; - if (pIE->length > sizeof(struct HT_info_element)) + if (pIE->length != sizeof(struct HT_info_element)) return; pHT_info = (struct HT_info_element *)pIE->data; @@ -1286,15 +1286,23 @@ void update_beacon_info(struct adapter *padapter, u8 *pframe, uint pkt_len, stru unsigned int len; struct ndis_80211_var_ie *pIE; + if (pkt_len < _BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN) + return; + len = pkt_len - (_BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN); for (i = 0; i < len;) { + if (i + sizeof(*pIE) > len) + break; pIE = (struct ndis_80211_var_ie *)(pframe + (_BEACON_IE_OFFSET_ + WLAN_HDR_A3_LEN) + i); + if (i + sizeof(*pIE) + pIE->length > len) + break; switch (pIE->element_id) { case WLAN_EID_VENDOR_SPECIFIC: /* to update WMM parameter set while receiving beacon */ - if (!memcmp(pIE->data, WMM_PARA_OUI, 6) && pIE->length == WLAN_WMM_LEN) /* WMM */ + if (pIE->length == WLAN_WMM_LEN && + !memcmp(pIE->data, WMM_PARA_OUI, 6)) /* WMM */ if (WMM_param_handler(padapter, pIE)) report_wmm_edca_update(padapter); @@ -1314,7 +1322,7 @@ void update_beacon_info(struct adapter *padapter, u8 *pframe, uint pkt_len, stru break; } - i += (pIE->length + 2); + i += sizeof(*pIE) + pIE->length; } } -- 2.53.0