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Tue, 05 May 2026 10:22:23 -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 1/2] staging: rtl8723bs: fix OOB write and read in HT_caps_handler() Date: Tue, 5 May 2026 19:22:13 +0200 Message-ID: <20260505172214.3650398-2-hossu.alexandru@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260505172214.3650398-1-hossu.alexandru@gmail.com> References: <20260428091621.739680-1-hossu.alexandru@gmail.com> <20260505172214.3650398-1-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 HT_caps_handler() iterates over pIE->length bytes and writes into HT_caps.u.HT_cap[], a fixed array of sizeof(struct HT_caps_element) bytes. pIE->length is a raw u8 from an over-the-air 802.11 Association Response frame and is never validated before the loop. A malicious AP can set it to 255, writing up to 229 bytes past the end of the array into adjacent fields of struct mlme_ext_info. Additionally, after the loop the function calls three macros that unconditionally read pIE->data[0] and pIE->data[1]: GET_HT_CAPABILITY_ELE_LDPC_CAP(pIE->data) -- reads data[0], bit 0 GET_HT_CAPABILITY_ELE_TX_STBC(pIE->data) -- reads data[0], bit 7 GET_HT_CAPABILITY_ELE_RX_STBC(pIE->data) -- reads data[1], bits 0-1 If a malicious AP sends an HT Capabilities IE with pIE->length less than 2, both bytes the macros need are outside the IE payload, causing an out-of-bounds read. Fix both issues: - Set HT_caps_enable = 1 first so HT negotiation is not regressed. - Return early if pIE->length < 2 to protect the macro reads. - Use umin() in the loop to bound the write side. The parallel HT_info_handler() already guards against oversized IEs. This patch applies the same discipline to HT_caps_handler(). Fixes: 554c0a3abf21 ("staging: Add rtl8723bs sdio wifi driver") Cc: stable@vger.kernel.org Signed-off-by: Alexandru Hossu --- Changes in v4: - Add pIE->length < 2 guard after HT_caps_enable = 1 to prevent OOB reads from GET_HT_CAPABILITY_ELE_LDPC_CAP/TX_STBC/RX_STBC macros that access pIE->data[0] and pIE->data[1] unconditionally. Caught by sashiko review of v3. - Use umin() in the loop bound to cap writes at sizeof(HT_caps.u.HT_cap) without bypassing HT_caps_enable. Changes in v3: - Switch from min_t() to umin() (Dan Carpenter). - Keep truncation approach rather than early return so HT_caps_enable is always set before the length check (Luka Gejak, AI review). Changes in v2: - Replace early return before HT_caps_enable = 1 with umin() truncation so HT mode is not disabled for APs with oversized IEs. drivers/staging/rtl8723bs/core/rtw_wlan_util.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c index 6a7c09db4cd9..98aa50357e96 100644 --- a/drivers/staging/rtl8723bs/core/rtw_wlan_util.c +++ b/drivers/staging/rtl8723bs/core/rtw_wlan_util.c @@ -936,7 +936,11 @@ void HT_caps_handler(struct adapter *padapter, struct ndis_80211_var_ie *pIE) pmlmeinfo->HT_caps_enable = 1; - for (i = 0; i < (pIE->length); i++) { + if (pIE->length < 2) + return; + + for (i = 0; i < umin(pIE->length, + sizeof(pmlmeinfo->HT_caps.u.HT_cap)); i++) { if (i != 2) { /* Commented by Albert 2010/07/12 */ /* Got the endian issue here. */ -- 2.53.0