netdev - [PATCH] decnet: fix DN_IFREQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190126201219.14934-1-johannes@sipsolutions.net>
Date:   Sat, 26 Jan 2019 21:12:19 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     netdev@...r.kernel.org
Cc:     viro@...iv.linux.org.uk, linux-decnet-user@...ts.sourceforge.net,
        Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH] decnet: fix DN_IFREQ_SIZE

From: Johannes Berg <johannes.berg@...el.com>

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@...el.com>
---
 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 d0b3e69c6b39..0962f9201baa 100644
--- a/net/decnet/dn_dev.c
+++ b/net/decnet/dn_dev.c
@@ -56,7 +56,7 @@
 #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};
-- 
2.17.2