URL:
<http://savannah.gnu.org/bugs/?51402>
Summary: SEGFAULT when querying 'info' on detached screen
Project: GNU Screen
Submitted by: None
Submitted on: Thu 06 Jul 2017 01:53:12 PM UTC
Category: Crash/Freeze/Infloop
Severity: 3 - Normal
Priority: 5 - Normal
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
Release: None
Fixed Release: None
Planned Release: 4.5.1
Work Required: None
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Details:
repro:
$ screen -d sleep 9999
$ screen -Q info
$ screen -ls
There are screens on:
28239.pts-101.XXX-queryA (05/04/17 09:24:25) (Dead ???)
28239.pts-101.XXX (05/04/17 09:24:25) (Dead ???)
Remove dead screens with 'screen -wipe'.
Unfortunately in Debian there are only very old debug symbol files of version
4.2.1 (but I can also repro on 4.5.0), so gdb trace is from the old version:
(gdb) c
Continuing.
Program received signal SIGSEGV, Segmentation fault.
0x0807a564 in ShowInfo () at process.c:5647
5647 process.c: No such file or directory.
(gdb) bt
#0 0x0807a564 in ShowInfo () at process.c:5647
#1 DoAction (act=0xfff8600b, key=-1) at process.c:1857
#2 0x08080b61 in DoCommand (argv=0xfff8707c, argl=0xfff8717c) at
process.c:4567
#3 0x0805ff59 in DoCommandMsg (mp=0x80bb000 <m>) at socket.c:1807
#4 0x080620f1 in ReceiveMsg () at socket.c:1220
#5 0x08090630 in sched () at sched.c:237
#6 0x0804c463 in main (ac=<optimized out>, av=<optimized out>) at
screen.c:1487
(gdb) show directories
Source directories searched: $cdir:$cwd
(gdb) dir /tmp/screen-4.2.1
Source directories searched: /tmp/screen-4.2.1:$cdir:$cwd
(gdb) l
warning: Source file is more recent than executable.
5642 }
5643 # ifdef UTF8
5644 if (wp->w_encoding != UTF8)
5645 # endif
5646 # endif
5647 if (D_CC0 || (D_CS0 && *D_CS0))
5648 {
5649 if (wp->w_gr == 2)
5650 {
5651 sprintf(p, " G%c", wp->w_Charset + '0');
(gdb) info registers
eax 0x0 0
ecx 0x7 7
edx 0x80cb2d8 135049944
ebx 0xfff8600b -499701
esp 0xfff85f70 0xfff85f70
ebp 0x0 0x0
esi 0x1 1
edi 0x0 0
eip 0x807a564 0x807a564 <DoAction+20740>
eflags 0x10246 [ PF ZF IF RF ]
cs 0x23 35
ss 0x2b 43
ds 0x2b 43
es 0x2b 43
fs 0x0 0
gs 0x63 99
Clearly there is an invalid dereference most likely due to uninitialized
variables when screen is started in detached state.
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