[PATCH 4.4 099/241] brcm80211: potential NULL dereference in brcmf_cfg80211_vndr_cmds_dcmd_handler()

From: Greg Kroah-Hartman
Date: Sun Jun 09 2019 - 13:06:23 EST

[ Upstream commit e025da3d7aa4770bb1d1b3b0aa7cc4da1744852d ]

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

Fixes: 1bacb0487d0e ("brcmfmac: replace cfg80211 testmode with vendor command")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/wireless/brcm80211/brcmfmac/vendor.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/vendor.c b/drivers/net/wireless/brcm80211/brcmfmac/vendor.c
index 8eff2753abade..d493021f60318 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/vendor.c
+++ b/drivers/net/wireless/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);
- 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;