ethtool: Fix potential kernel buffer overflow in ETHTOOL_GRXCLSRLALL

On a 32-bit machine, info.rule_cnt >= 0x40000000 leads to integer
overflow and the buffer may be smaller than needed.  Since
ETHTOOL_GRXCLSRLALL is unprivileged, this can presumably be used for at
least denial of service.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index a0f4964033d2..a3a7e9a48dff 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -347,8 +347,9 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
 
         if (info.cmd == ETHTOOL_GRXCLSRLALL) {
                 if (info.rule_cnt > 0) {
-                        rule_buf = kmalloc(info.rule_cnt * sizeof(u32),
-                                           GFP_USER);
+                        if (info.rule_cnt <= KMALLOC_MAX_SIZE / sizeof(u32))
+                                rule_buf = kmalloc(info.rule_cnt * sizeof(u32),
+                                                   GFP_USER);
                         if (!rule_buf)
                                 return -ENOMEM;
                 }