brcm80211: potential NULL dereference in brcmf_cfg80211_vndr_cmds_dcmd_handler()

If "ret_len" is negative then it could lead to a NULL dereference.

The "ret_len" value comes from nl80211_vendor_cmd(), if it's negative
then we don't allocate the "dcmd_buf" buffer.  Then we pass "ret_len" to
brcmf_fil_cmd_data_set() where it is cast to a very high u32 value.
Most of the functions in that call tree check whether the buffer we pass
is NULL but there are at least a couple places which don't such as
brcmf_dbg_hex_dump() and brcmf_msgbuf_query_dcmd().  We memcpy() to and
from the buffer so it would result in a NULL dereference.

The fix is to change the types so that "ret_len" can't be negative.  (If
we memcpy() zero bytes to NULL, that's a no-op and doesn't cause an
issue).

Fixes: 1bacb0487d0e ("brcmfmac: replace cfg80211 testmode with vendor command")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/vendor.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/vendor.c
index 8eff2753abadeb2704f87f88f7c5eabd75bf091b..d493021f6031852b478706022418293ab8939090 100644 (file)
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/vendor.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/vendor.c
@@ -35,9 +35,10 @@ static int brcmf_cfg80211_vndr_cmds_dcmd_handler(struct wiphy *wiphy,
        struct brcmf_if *ifp;
        const struct brcmf_vndr_dcmd_hdr *cmdhdr = data;
        struct sk_buff *reply;
-       int ret, payload, ret_len;
+       unsigned int payload, ret_len;
        void *dcmd_buf = NULL, *wr_pointer;
        u16 msglen, maxmsglen = PAGE_SIZE - 0x100;
+       int ret;
 
        if (len < sizeof(*cmdhdr)) {
                brcmf_err("vendor command too short: %d\n", len);
@@ -65,7 +66,7 @@ static int brcmf_cfg80211_vndr_cmds_dcmd_handler(struct wiphy *wiphy,
                        brcmf_err("oversize return buffer %d\n", ret_len);
                        ret_len = BRCMF_DCMD_MAXLEN;
                }
-               payload = max(ret_len, len) + 1;
+               payload = max_t(unsigned int, ret_len, len) + 1;
                dcmd_buf = vzalloc(payload);
                if (NULL == dcmd_buf)
                        return -ENOMEM;