From 7c1611780823b76219cb1478db53dfd890c4a9a2 Mon Sep 17 00:00:00 2001 From: Tianchu Chen Date: Fri, 4 Sep 2026 15:23:34 +0000 Subject: [PATCH] wifi: cw1200: fix TX padding OOB read leaking heap data to device The TX path rounds the transfer size up to the bus alignment (align_size(), up to 511 bytes for SDIO, 1 byte for SPI) but sends the padded length straight from the frame buffer, which has no room reserved for the padding. cw1200_data_write() therefore reads past the end of the frame and the bus transfer carries those bytes to the device. A bogus device can collect up to 511 bytes of kernel heap data per TX frame. The RX path does not have this problem: it allocates the skb with the aligned length (alloc_len) before reading. Compute the exact padding with the bus align_size() callback, make sure queued TX frames have tailroom for it, and zero the padding bytes before the transfer so nothing past the frame is exposed. This is not expected to change driver behavior on most cases: frame contents and transfer sizes are unchanged, only the content of the padding bytes (previously undefined stale memory, now zero), which the device never reads since the WSM header carries the real frame length. The skb expansion can only fail under memory exhaustion, in which case the frame is dropped like on the existing error paths of cw1200_tx(). Discovered by Atuin - Automated Vulnerability Discovery Engine. Fixes: a910e4a94f69 ("cw1200: add driver for the ST-E CW1100 & CW1200 WLAN chipsets") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Tianchu Chen Link: https://patch.msgid.link/7982b4a7e64f74e2068790ec389ca680a081f730@linux.dev Signed-off-by: Johannes Berg --- drivers/net/wireless/st/cw1200/bh.c | 8 +++++++- drivers/net/wireless/st/cw1200/txrx.c | 14 ++++++++++++++ 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/drivers/net/wireless/st/cw1200/bh.c b/drivers/net/wireless/st/cw1200/bh.c index b034bab4b489..9367a981f1de 100644 --- a/drivers/net/wireless/st/cw1200/bh.c +++ b/drivers/net/wireless/st/cw1200/bh.c @@ -344,6 +344,7 @@ static int cw1200_bh_tx_helper(struct cw1200_common *priv, int *tx_burst) { size_t tx_len; + size_t aligned_len; u8 *data; int ret; struct wsm_hdr *wsm; @@ -376,9 +377,14 @@ static int cw1200_bh_tx_helper(struct cw1200_common *priv, atomic_inc(&priv->bh_tx); - tx_len = priv->hwbus_ops->align_size( + aligned_len = priv->hwbus_ops->align_size( priv->hwbus_priv, tx_len); + /* Zero the bus alignment padding so no stale data is sent. */ + if (aligned_len > tx_len) + memset(data + tx_len, 0, aligned_len - tx_len); + tx_len = aligned_len; + /* Check if not exceeding CW1200 capabilities */ if (WARN_ON_ONCE(tx_len > EFFECTIVE_BUF_SIZE)) pr_debug("Write aligned len: %zu\n", tx_len); diff --git a/drivers/net/wireless/st/cw1200/txrx.c b/drivers/net/wireless/st/cw1200/txrx.c index 084d52b11f5b..e13695667a00 100644 --- a/drivers/net/wireless/st/cw1200/txrx.c +++ b/drivers/net/wireless/st/cw1200/txrx.c @@ -14,6 +14,7 @@ #include "wsm.h" #include "bh.h" #include "sta.h" +#include "hwbus.h" #include "debug.h" #define CW1200_INVALID_RATE_ID (0xFF) @@ -716,6 +717,7 @@ void cw1200_tx(struct ieee80211_hw *dev, struct ieee80211_sta *sta; struct wsm_tx *wsm; bool tid_update = false; + size_t pad_len; u8 flags = 0; int ret; @@ -764,6 +766,18 @@ void cw1200_tx(struct ieee80211_hw *dev, sta = t.sta; + /* + * The bus transfer is padded up to the bus alignment and the + * padding is transferred from the frame buffer. Make sure the + * buffer has room for the padding so the device never receives + * data past the end of the frame. + */ + pad_len = priv->hwbus_ops->align_size(priv->hwbus_priv, skb->len) - + skb->len; + if (skb_tailroom(skb) < pad_len && + pskb_expand_head(skb, 0, pad_len, GFP_ATOMIC)) + goto drop; + spin_lock_bh(&priv->ps_state_lock); { tid_update = cw1200_tx_h_pm_state(priv, &t);