Re: [PATCH] iproute2: Conforming to -D_FORTIFY_SOURCE=2 restrictions

Stephen,

 You can reproduce this issue in 2.6.37 like below. And the previous
gdb log is after the install the debuginfo package in SUSE.

# ip -6 xfrm state add src 3ffe:501:ffff:ff03:21a:64ff:fe12:e4c1 dst
3ffe:501:ffff:ff05:200:ff:fe00:c1c1 proto ah spi 0x1000 mode transport
auth md5 "TAHITEST89ABCDEF"

*** buffer overflow detected ***: ip terminated
======= Backtrace: =========
/lib/libc.so.6(__fortify_fail+0x40)[0xb76d0070]
/lib/libc.so.6(+0xe8e27)[0xb76cde27]
/lib/libc.so.6(+0xe8317)[0xb76cd317]
ip[0x806d6c4]
ip(do_xfrm_state+0x120)[0x806dc70]
ip(do_xfrm+0x81)[0x806ad51]
ip[0x804c355]
ip(main+0x476)[0x804caa6]
/lib/libc.so.6(__libc_start_main+0xfe)[0xb75fbc2e]
ip[0x804c261]
======= Memory map: ========
08048000-08087000 r-xp 00000000 08:01 4465       /sbin/ip
08087000-08088000 r--p 0003e000 08:01 4465       /sbin/ip
08088000-0808a000 rw-p 0003f000 08:01 4465       /sbin/ip
0808a000-080ad000 rw-p 00000000 00:00 0          [heap]
b75c6000-b75e2000 r-xp 00000000 08:01 131084     /lib/libgcc_s.so.1
b75e2000-b75e3000 r--p 0001b000 08:01 131084     /lib/libgcc_s.so.1
b75e3000-b75e4000 rw-p 0001c000 08:01 131084     /lib/libgcc_s.so.1
b75e4000-b75e5000 rw-p 00000000 00:00 0
b75e5000-b774b000 r-xp 00000000 08:01 131375     /lib/libc-2.11.3.so
b774b000-b774c000 ---p 00166000 08:01 131375     /lib/libc-2.11.3.so
b774c000-b774e000 r--p 00166000 08:01 131375     /lib/libc-2.11.3.so
b774e000-b774f000 rw-p 00168000 08:01 131375     /lib/libc-2.11.3.so
b774f000-b7752000 rw-p 00000000 00:00 0
b7752000-b7755000 r-xp 00000000 08:01 131428     /lib/libdl-2.11.3.so
b7755000-b7756000 r--p 00002000 08:01 131428     /lib/libdl-2.11.3.so
b7756000-b7757000 rw-p 00003000 08:01 131428     /lib/libdl-2.11.3.so
b7774000-b7775000 rw-p 00000000 00:00 0
b7775000-b7794000 r-xp 00000000 08:01 154467     /lib/ld-2.11.3.so
b7794000-b7795000 r--p 0001e000 08:01 154467     /lib/ld-2.11.3.so
b7795000-b7796000 rw-p 0001f000 08:01 154467     /lib/ld-2.11.3.so
bfa02000-bfa23000 rw-p 00000000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]
Aborted

And If without -D_FORTIFY_SOURCE=2 in gcc, it works fine, so It's a
bug in iproute2 which is not conforming to -D_FORTIFY_SOURCE=2
restrictions.

Thanks!

On Mon, Oct 17, 2011 at 11:23 PM, Stephen Hemminger
[off-list ref] wrote:

On Mon, 17 Oct 2011 15:35:35 +0800
Bin Li [off-list ref] wrote:

quoted

(gdb) l
161                     len = slen;
162                     if (len > 0) {
163                             if (len > max)
164                                     invarg("\"ALGOKEY\" makes buffer
overflow\n", key);
165
166                             strncpy(buf, key, len);
167                     }
168             }
169
170             alg->alg_key_len = len * 8;
(gdb) up
#8  xfrm_state_modify (cmd=<optimized out>, flags=<optimized out>, argc=1,
    argv=0x7fffffffe370) at xfrm_state.c:406
406                                     xfrm_algo_parse((void *)&alg, type,
name, key,

the compiler passes zero to __builtin___strncpy_chk as the buffer size.
xfrm_algo_parse is inlined into xfrm_state_modify.

I don't understand, looks like a compiler bug. Call strncpy with
0 length should not be possible since the check was  3 lines
before for len > 0.