[PATCH 5.12 142/296] net: dsa: fix a crash if ->get_sset_count() fails

Greg Kroah-Hartman
2021-05-31T16:24:37Z

From: Dan Carpenter <dan.carpenter@oracle.com>

commit a269333fa5c0c8e53c92b5a28a6076a28cde3e83 upstream.

If ds->ops->get_sset_count() fails then it "count" is a negative error
code such as -EOPNOTSUPP. Because "i" is an unsigned int, the negative
error code is type promoted to a very high value and the loop will
corrupt memory until the system crashes.

Fix this by checking for error codes and changing the type of "i" to
just int.

Fixes: badf3ada60ab ("net: dsa: Provide CPU port statistics to master netdev")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/dsa/master.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -147,8 +147,7 @@ static void dsa_master_get_strings(struc
struct dsa_switch *ds = cpu_dp->ds;
int port = cpu_dp->index;
int len = ETH_GSTRING_LEN;
- int mcount = 0, count;
- unsigned int i;
+ int mcount = 0, count, i;
uint8_t pfx[4];
uint8_t *ndata;

@@ -178,6 +177,8 @@ static void dsa_master_get_strings(struc
*/
ds->ops->get_strings(ds, port, stringset, ndata);
count = ds->ops->get_sset_count(ds, port, stringset);
+ if (count < 0)
+ return;
for (i = 0; i < count; i++) {
memmove(ndata + (i * len + sizeof(pfx)),
ndata + i * len, len - sizeof(pfx));