2014-12-11 11:04 GMT-02:00 Paulo César Pereira de Andrade
<[email protected]>:
> Hi,
Hi again and ping.
> I have this test case:
>
> ---8<---
> #!/bin/ksh
> toto="s"
> alarm -r alarm_handler +1
> function alarm_handler.alarm
> {
> if [[ $toto == "s" ]]
> then
> toto="e"
> else
> toto="f"
> fi
> }
> IFS=","
> (echo "2";sleep 1;echo "3") | while IFS="," read arg1
> #(echo "2";sleep 1;echo "3") | while read arg1
> do
> print "$arg1"
> done
> ---8<---
>
> provided by a user. The test case causes it to start reading
> random memory in src/cmd/ksh93/bltins/read.c in this chunk
> of sh_readline:
>
> ---%<---
> /* skip over word characters */
> wrd = -1;
> while(1)
> {
> while((c=shp->ifstable[*cp++])==0) <<<=== HERE
> if(!wrd)
> wrd = 1;
> ---%<---
>
> A example gdb session after finding the root of the problem is:
>
> ---%<---
> $ gdb --args /home/pcpa/rhel/ksh/ksh-20120801/arch/linux.i386-64/bin/ksh
> t2.ksh
> GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-51.el7
> Copyright (C) 2013 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law. Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-redhat-linux-gnu".
> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from
> /home/pcpa/rhel/ksh/ksh-20120801/arch/linux.i386-64/bin/ksh...done.
> (gdb) b sh_readline
> Breakpoint 1 at 0x4825f9: file
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c, line
> 215.
> (gdb) r
> Starting program:
> /home/pcpa/rhel/ksh/ksh-20120801/arch/linux.i386-64/bin/ksh t2.ksh
> Detaching after fork from child process 11872.
>
> Breakpoint 1, sh_readline (shp=0x795300 <sh>, names=0x7ffff7fae9a8,
> fd=0, flags=0, size=0, timeout=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:215
> 215 char was_escape = 0;
> Missing separate debuginfos, use: debuginfo-install
> glibc-2.17-55.el7_0.1.x86_64
> (gdb) p &shp->ifstable [0]
> $1 = 0x795930 <sh+1584> ""
> (gdb) watch *(char*)$1
> Hardware watchpoint 2: *(char*)$1
> (gdb) p $1
> $2 = 0x795930 <sh+1584> ""
> (gdb) c
> Continuing.
> Hardware watchpoint 2: *(char*)$1
>
> Old value = 0 '\000'
> New value = 2 '\002'
> sh_readline (shp=0x7fffffffc0dc, names=0x7ffff7fae9b0, fd=0, flags=0,
> size=0, timeout=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:310
> 310 if((flags&SS_FLAG))
> (gdb) bt
> #0 sh_readline (shp=0x7fffffffc0dc, names=0x7ffff7fae9b0, fd=0,
> flags=0, size=0, timeout=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:310
> #1 0x00000000004824ef in b_read (argc=2, argv=0x7ffff7fae9a8,
> context=0x795810 <sh+1296>)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:177
> #2 0x0000000000466b98 in sh_exec (t=0x7fffffffc0dc, flags=512) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:1410
> #3 0x000000000046a326 in sh_exec (t=0x7fffffffc0dc, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:2485
> #4 0x0000000000468847 in sh_exec (t=0x7fffffffc0dc, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:1978
> #5 0x00000000004693d2 in sh_exec (t=0x7fffffffc0dc, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:2195
> #6 0x000000000040738f in exfile (shp=0x7fffffffc0dc,
> iop=0x7ffff7f930e1, fno=0) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/main.c:581
> #7 0x0000000000406847 in sh_main (ac=2, av=0x7fffffffe0a8,
> userinit=0x0) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/main.c:353
> #8 0x0000000000405c55 in main (argc=2, argv=0x7fffffffe0a8) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/pmain.c:45
> (gdb) c
> Continuing.
> Hardware watchpoint 2: *(char*)$1
>
> Old value = 2 '\002'
> New value = 0 '\000'
> 0x00007ffff739bc1f in __memset_sse2 () from /lib64/libc.so.6
> (gdb) bt
> #0 0x00007ffff739bc1f in __memset_sse2 () from /lib64/libc.so.6
> #1 0x0000000000421cd3 in get_ifs (np=0x7ffff7fb0b38,
> fp=0x7ffff7fb0610) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/init.c:546
> #2 0x0000000000407a49 in nv_getv (np=0x7ffff7fb0b38, nfp=0x795930
> <sh+1584>) at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/nvdisc.c:58
> #3 0x0000000000448b6e in nv_getval (np=0x7ffff7fb0b38) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/name.c:2801
> #4 0x0000000000447da2 in table_unset (shp=0x795300 <sh>,
> root=0x7ffff7f93290, flags=524289, oroot=0x7ffff7fcaf80)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/name.c:2446
> #5 0x000000000044ab37 in sh_unscope (shp=0x795300 <sh>) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/name.c:3548
> #6 0x000000000046d760 in sh_funscope (argn=1, argv=0x7fffffffb9c8,
> fun=0x0, arg=0x7fffffffb8e0, execflg=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:3482
> #7 0x000000000046dc27 in sh_funct (shp=0x795300 <sh>,
> np=0x7ffff7f92910, argn=1, argv=0x7fffffffb9c8, envlist=0x0,
> execflg=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:3556
> #8 0x000000000046e1dd in sh_fun (np=0x7ffff7f92910,
> nq=0x7ffff7f92240, argv=0x7fffffffb9c8)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:3630
> #9 0x000000000047952c in sh_timetraps (shp=0x795300 <sh>) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/alarm.c:144
> #10 0x00000000004794ab in trap_timeout (handle=0x7ffff7f922d0) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/alarm.c:126
> #11 0x0000000000461456 in sigalrm (sig=14) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/timers.c:162
> #12 <signal handler called>
> #13 _sffilbuf (f=0x792dc0 <_Sfstdin>, n=-1) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/lib/libast/sfio/sffilbuf.c:94
> #14 0x00000000004e0556 in sfgetr (f=0x792dc0 <_Sfstdin>, rc=10,
> type=0) at /home/pcpa/rhel/ksh/ksh-20120801/src/lib/libast/sfio/sfgetr.c:81
> #15 0x0000000000483830 in sh_readline (shp=0x792dc0 <_Sfstdin>,
> names=0x7ffff7fae9b0, fd=0, flags=0, size=0, timeout=0)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:496
> #16 0x00000000004824ef in b_read (argc=2, argv=0x7ffff7fae9a8,
> context=0x795810 <sh+1296>)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/bltins/read.c:177
> #17 0x0000000000466b98 in sh_exec (t=0x792dc0 <_Sfstdin>, flags=512)
> at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:1410
> #18 0x000000000046a326 in sh_exec (t=0x792dc0 <_Sfstdin>, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:2485
> #19 0x0000000000468847 in sh_exec (t=0x792dc0 <_Sfstdin>, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:1978
> #20 0x00000000004693d2 in sh_exec (t=0x792dc0 <_Sfstdin>, flags=4) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/xec.c:2195
> #21 0x000000000040738f in exfile (shp=0x792dc0 <_Sfstdin>, iop=0x1,
> fno=65536) at /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/main.c:581
> #22 0x0000000000406847 in sh_main (ac=2, av=0x7fffffffe0a8,
> userinit=0x0) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/main.c:353
> #23 0x0000000000405c55 in main (argc=2, argv=0x7fffffffe0a8) at
> /home/pcpa/rhel/ksh/ksh-20120801/src/cmd/ksh93/sh/pmain.c:45
> (gdb) q
> A debugging session is active.
>
> Inferior 1 [process 11868] will be killed.
>
> Quit anyway? (y or n) y
> ---%<---
>
> The code "memset(shp->ifstable,0,(1<<CHAR_BIT));" in
> src/cmd/ksh93/sh/init.c:get_ifs()
> is causing it to not stop when reading a null byte.
>
> The attached patch corrects the problem, but I think an alternative
> that could be
> better would be to save/restore shp->ifstable in the signal handler,
> or a function
> called by it.
>
> On a normal run, shp->ifstable would be:
> {2,0,0,0,0,0,0,0,0,0,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,39,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,}
> but if the alarm signal handler is called, it would become, without the patch:
> {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,}
>
> The patch force 0 as 2 (S_EOF), and remaining differences are
> 3 at offset 10, 39 at offset 92.
>
> Do you think it would be better to save/restore shp->ifstable in
> the alarm handler? src/cmd/ksh93/sh/timers.c:sigalrm()
> or some other alternative? for example, adding hardcoded
> shp->ifstable['\n'] = S_NL;
> shp->ifstable['\\'] = S_ESC;
> (what looks like extra sensible hardcoded defaults),
> or not calling memset.
I believe the new attached patch my be better, but I still
think it requires some review from some ksh internals
expert.
Looking at sh_trap() I believe I may need at least more an
...
Fcin_t savefc;
fcsave(&savefc);
<<<current patch>>>
fcrestore(&savefc);
...
but may also need to save/restore other state. Alarms are
kind of a trap anyway...
Thanks,
Paulo
diff -up ksh-20120801/src/cmd/ksh93/bltins/alarm.c.orig ksh-20120801/src/cmd/ksh93/bltins/alarm.c
--- ksh-20120801/src/cmd/ksh93/bltins/alarm.c.orig 2014-12-18 12:03:39.198461933 -0200
+++ ksh-20120801/src/cmd/ksh93/bltins/alarm.c 2014-12-18 12:04:32.464421268 -0200
@@ -130,6 +130,7 @@ void sh_timetraps(Shell_t *shp)
{
register struct tevent *tp, *tpnext;
register struct tevent *tptop;
+ char ifstable[256];
while(1)
{
shp->sigflag[SIGALRM] &= ~SH_SIGALRM;
@@ -141,7 +142,11 @@ void sh_timetraps(Shell_t *shp)
{
tp->flags &= ~L_FLAG;
if(tp->action)
+ {
+ memcpy(ifstable,shp->ifstable,sizeof(ifstable));
sh_fun(tp->action,tp->node,(char**)0);
+ memcpy(shp->ifstable,ifstable,sizeof(ifstable));
+ }
tp->flags &= ~L_FLAG;
if(!tp->flags)
{
diff -up ksh-20120801/src/cmd/ksh93/sh/timers.c.orig ksh-20120801/src/cmd/ksh93/sh/timers.c
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