bug#28859: Segmentation fault with NULL pointer dereference in 'stty'

[Pádraig Brady]

On 15/10/17 18:07, Jaeseung Choi wrote:
> Dear GNU team,
> 
> While testing coreutils for a research purpose, we found the following
> crash in 'stty'. Running stty with the command-line "stty eol -F AA"
> raises a crash as below. We did not change any terminal setting, and
> believe the bug is irrelevant from any specific terminal
> configuration.
> 
> address@hidden:~$ tar -xf coreutils-8.28.tar.xz
> address@hidden:~$ cd coreutils-8.28/
> address@hidden:~/coreutils-8.28$ mkdir obj
> address@hidden:~/coreutils-8.28$ cd obj
> address@hidden:~/coreutils-8.28/obj$ ../configure --disable-nls && make
> ...
> address@hidden:~/coreutils-8.28/obj$ gdb ./src/stty -q
> Reading symbols from ./src/stty...done.
> (gdb) run eol -F AA
> Starting program: /home/jason/coreutils-8.28/obj/src/stty eol -F AA
> 
> Program received signal SIGSEGV, Segmentation fault.
> set_control_char (info=0x40a6f8 <control_info+120>, info=0x40a6f8
> <control_info+120>, mode=0x6103c0 <check_mode>, arg=0x0) at
> ../src/stty.c:1695
> 1695      else if (arg[0] == '\0' || arg[1] == '\0')
> (gdb) x/i $rip
> => 0x40387a <apply_settings+746>:       movzbl (%rbx),%r14d
> (gdb) info reg rbx
> rbx            0x0      0
> (gdb)
> 
> We could reproduce the bug in coreutils from version 8.27 to 8.28.
> Also, the bug was reproducible in both Ubuntu 16.04 and Debian 9.1.
> But the stty program pre-built in Debian 9.1 did not crash because
> currently 8.26 version is installed in Debian.

This is actually an old bug which you can reproduce with -F /dev/tty.
The attached should fix it up.

thanks!
Pádraig

stty-crash.patch
Description: Text Data