From: Johannes Berg johannes.berg@intel.com
[ Upstream commit 50c2936634bcb1db78a8ca63249236810c11a80f ]
Digging through the ioctls with Al because of the previous patches, we found that on 64-bit decnet's dn_dev_ioctl() is wrong, because struct ifreq::ifr_ifru is actually 24 bytes (not 16 as expected from struct sockaddr) due to the ifru_map and ifru_settings members.
Clearly, decnet expects the ioctl to be called with a struct like struct ifreq_dn { char ifr_name[IFNAMSIZ]; struct sockaddr_dn ifr_addr; };
since it does struct ifreq *ifr = ...; struct sockaddr_dn *sdn = (struct sockaddr_dn *)&ifr->ifr_addr;
This means that DN_IFREQ_SIZE is too big for what it wants on 64-bit, as it is sizeof(struct ifreq) - sizeof(struct sockaddr) + sizeof(struct sockaddr_dn)
This assumes that sizeof(struct sockaddr) is the size of ifr_ifru but that isn't true.
Fix this to use offsetof(struct ifreq, ifr_ifru).
This indeed doesn't really matter much - the result is that we copy in/out 8 bytes more than we should on 64-bit platforms. In case the "struct ifreq_dn" lands just on the end of a page though it might lead to faults.
As far as I can tell, it has been like this forever, so it seems very likely that nobody cares.
Signed-off-by: Johannes Berg johannes.berg@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/decnet/dn_dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c index b2c26b081134a..80554e7e9a0f6 100644 --- a/net/decnet/dn_dev.c +++ b/net/decnet/dn_dev.c @@ -55,7 +55,7 @@ #include <net/dn_neigh.h> #include <net/dn_fib.h>
-#define DN_IFREQ_SIZE (sizeof(struct ifreq) - sizeof(struct sockaddr) + sizeof(struct sockaddr_dn)) +#define DN_IFREQ_SIZE (offsetof(struct ifreq, ifr_ifru) + sizeof(struct sockaddr_dn))
static char dn_rt_all_end_mcast[ETH_ALEN] = {0xAB,0x00,0x00,0x04,0x00,0x00}; static char dn_rt_all_rt_mcast[ETH_ALEN] = {0xAB,0x00,0x00,0x03,0x00,0x00};