Bug 585696 – app-misc/screen-4.3.1-r1: segmentation fault on command if argument length >=21 (e.g. screen-256color-bce-s)

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Andrew Savchenko 2016-06-12 13:29:58 UTC]

Created attachment 437250 [details]
emerge --info

Hi,

screen-4.3.1-r1 segfaults if term is set to a value longer than 20 chars, e.g.:

$ cat ~/.screenrc
term screen-256color-bce-s

Here is backtrace:

# gdb /usr/bin/screen core
[...]
Core was generated by `/usr/bin/SCREEN'.
Program terminated with signal SIGABRT, Aborted.
#0  0xa76e6bd1 in __kernel_vsyscall ()
(gdb) bt
#0  0xa76e6bd1 in __kernel_vsyscall ()
#1  0xa74860c9 in raise () from /lib/libc.so.6
#2  0xa74877e4 in abort () from /lib/libc.so.6
#3  0x0804df59 in CoreDump (sigsig=11) at screen.c:1717
#4  <signal handler called>
#5  0x0806d8c3 in MakeTermcap (aflag=0) at termcap.c:947
#6  0x0807f77f in DoAction (act=act@entry=0xafe469ac, key=key@entry=-1) at process.c:2684
#7  0x08084123 in DoCommand (argv=argv@entry=0xafe469ec, argl=argl@entry=0xafe46aec) at process.c:4662
#8  0x08059615 in RcLine (ubuf=ubuf@entry=0xafe46c1c "term", ubufl=ubufl@entry=2048) at fileio.c:385
#9  0x0805a548 in FinishRc (rcfilename=0x0) at fileio.c:330
#10 0x0804c885 in main (ac=<optimized out>, av=<optimized out>) at screen.c:1440

For debugging program was build using CFLAGS="-O2 -pipe -ggdb3".

Looks like the reason comes from termcap.c:75:
char screenterm[20];        /* new $TERM, usually "screen" */

I'll test a fix and will report back later.

[Comment 1 Andrew Savchenko 2016-06-12 13:34:45 UTC]

And this is how screen is configured:

$ eix -e screen
[...]
     Installed versions:  4.3.1-r1{tbz2}(03:44:08 PM 06/12/2016)(pam -debug -multiuser -nethack -selinux)

[Comment 2 Andrew Savchenko 2016-06-12 13:43:19 UTC]

> Looks like the reason comes from termcap.c:75:
> char screenterm[20];        /* new $TERM, usually "screen" */

Indeed this is the cause. Patch below fixes segfault.

[Comment 3 Andrew Savchenko 2016-06-12 13:44:04 UTC]

Created attachment 437252 [details, diff]
screen-4.3.1-term-length.patch

[Comment 4 Andrew Savchenko 2016-06-12 14:34:43 UTC]

Created attachment 437260 [details, diff]
screen-4.3.1-termlen.patch

screenterm length is actually hardcoded in more places...

Upstream already fixed this issue in git:
http://git.savannah.gnu.org/cgit/screen.git/commit/?id=37ca949e462a7608572f653848b5a7554964fd53

However, upstream patch doesn't apply to 4.3.1, because many code changes were made. So I backported commit mentioned above to 4.3.1.

Seems to work fine here.

[Comment 5 Andrew Savchenko 2016-06-19 21:22:51 UTC]

This issue was kindly fixed by upstream in the new screen-4.4.0 release.

[Comment 6 Jeroen Roovers (RETIRED) 2016-06-26 09:51:01 UTC]

Fixed in 4.4.0.