From abb66a672f5575a328d05c0790403af673d0f76c Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Thu, 12 Apr 2012 11:18:39 -0400 Subject: tftp.h: rework layout to work with fortification The current tftp structure does not work when fortification is enabled. Starting with gcc-4.5, more size checking was added to trigger these. Older versions just didn't have enough information, so they returned -1 as the sizes. First, the tu_stuff field is declared as 1 byte (when it's really an arbitrary length C string), so attempting to strcpy() with it results in crashes. This fails with _FORTIFY_SOURCE=1. Second, even if we change that to [0] (since gcc does not allow flexible array members in an union), gcc is not smart enough to see that they are two overlapping flexible arrays (tu_stuff and tu_data), so it will still trigger an abort with _FORTIFY_SOURCE=2. This is because it thinks that tu_stuff is 0 bytes and tu_data comes after it. Talking to upstream gcc, they don't seem terribly inclined to fix the 2nd issue, but even if they did, we still have plenty of 4.5 and 4.6 installs that would hit problems. So, let's re-order with a few more anonymous structs & unions so that the fields are laid out with a zero-length array always as the last field. This seems to fix things with gcc-4.6, and the tftp-hpa pkg continues to build & work. URL: https://bugs.launchpad.net/ubuntu/+source/tftp-hpa/+bug/691345 URL: https://bugs.archlinux.org/task/28103 URL: https://bugs.gentoo.org/357083 URL: http://gcc.gnu.org/PR52944 Signed-off-by: Mike Frysinger --- inet/arpa/tftp.h | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) (limited to 'inet/arpa') diff --git a/inet/arpa/tftp.h b/inet/arpa/tftp.h index 21b0559e54..86e0b6e814 100644 --- a/inet/arpa/tftp.h +++ b/inet/arpa/tftp.h @@ -49,17 +49,23 @@ struct tftphdr { short th_opcode; /* packet type */ union { - unsigned short tu_block; /* block # */ - short tu_code; /* error code */ - char tu_stuff[1]; /* request packet stuff */ - } __attribute__ ((__packed__)) th_u; - char th_data[1]; /* data or error string */ + char tu_padding[3]; /* sizeof() compat */ + struct { + union { + unsigned short tu_block; /* block # */ + short tu_code; /* error code */ + } __attribute__ ((__packed__)) th_u3; + char tu_data[0]; /* data or error string */ + } __attribute__ ((__packed__)) th_u2; + char tu_stuff[0]; /* request packet stuff */ + } __attribute__ ((__packed__)) th_u1; } __attribute__ ((__packed__)); -#define th_block th_u.tu_block -#define th_code th_u.tu_code -#define th_stuff th_u.tu_stuff -#define th_msg th_data +#define th_block th_u1.th_u2.th_u3.tu_block +#define th_code th_u1.th_u2.th_u3.tu_code +#define th_stuff th_u1.tu_stuff +#define th_data th_u1.th_u2.tu_data +#define th_msg th_u1.th_u2.tu_data /* * Error codes. -- cgit v1.2.3