ethtool: ioctl: Fix out-of-bounds warning in store_link_ksettings_for_user()

Fix the following out-of-bounds warning:

net/ethtool/ioctl.c:492:2: warning: 'memcpy' offset [49, 84] from the object at 'link_usettings' is out of the bounds of referenced subobject 'base' with type 'struct ethtool_link_settings' at offset 0 [-Warray-bounds]

The problem is that the original code is trying to copy data into a
some struct members adjacent to each other in a single call to
memcpy(). This causes a legitimate compiler warning because memcpy()
overruns the length of &link_usettings.base. Fix this by directly
using &link_usettings and _from_ as destination and source addresses,
instead.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 27f1c52..3fa7a39 100644 (file)
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -489,7 +489,7 @@ store_link_ksettings_for_user(void __user *to,
 {
        struct ethtool_link_usettings link_usettings;
 
-       memcpy(&link_usettings.base, &from->base, sizeof(link_usettings));
+       memcpy(&link_usettings, from, sizeof(link_usettings));
        bitmap_to_arr32(link_usettings.link_modes.supported,
                        from->link_modes.supported,
                        __ETHTOOL_LINK_MODE_MASK_NBITS);