[PATCH] wireless: mt76: mt7921: Fix use-after-free in fw features query.

greearb
2023-03-08T01:00:41Z

From: Ben Greear <greearb@candelatech.com>

Stop referencing 'features' memory after release_firmware is called.

Fixes this crash:

RIP: 0010:mt7921_check_offload_capability+0x17d
mt7921_pci_probe+0xca/0x4b0
...

Signed-off-by: Ben Greear <greearb@candelatech.com>
---
drivers/net/wireless/mediatek/mt76/mt7921/init.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/init.c b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
index 38d6563cb12f..3b6fb1a6b351 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/init.c
@@ -171,6 +171,7 @@ u8 mt7921_check_offload_capability(struct device *dev, const char *fw_wm)
const struct firmware *fw;
int ret, i, offset = 0;
const u8 *data, *end;
+ u8 rv = 0;

ret = request_firmware(&fw, fw_wm, dev);
if (ret)
@@ -197,12 +198,17 @@ u8 mt7921_check_offload_capability(struct device *dev, const char *fw_wm)
data += sizeof(*rel_info);
end = data + le16_to_cpu(rel_info->len);

+ /* TODO: This needs better sanity checking I think.
+ * Likely a corrupted firmware with bad rel_info->len, for instance,
+ * would blow this up.
+ */
while (data < end) {
rel_info = (struct mt7921_realease_info *)data;
data += sizeof(*rel_info);

if (rel_info->tag == MT7921_FW_TAG_FEATURE) {
features = (struct mt7921_fw_features *)data;
+ rv = features->data;
break;
}

@@ -211,7 +217,7 @@ u8 mt7921_check_offload_capability(struct device *dev, const char *fw_wm)

release_firmware(fw);

- return features ? features->data : 0;
+ return rv;
}
EXPORT_SYMBOL_GPL(mt7921_check_offload_capability);

--
2.39.1