Re: Crash on valid input

[Dan Kegel <dank@xxxxxxxxx>]

Yes, my script was crap, I've fixed it.

Here's the reproducer.  Called with foo unset.  I think it doesn't
crash without -x.

#!/bin/dash
set -x
test ! $foo



On Mon, Apr 8, 2013 at 8:08 PM, Eric Blake <eblake@xxxxxxxxxx> wrote:
> On 04/08/2013 08:43 PM, Dan Kegel wrote:
>> If I check for an empty string like this:
>>
>> + test ! $foo
>
> You know, this is highly reliant on $foo expanding to either nothing (it
> is empty, so you are really invoking the one-argument form 'test !'
> which is true) or a single shell word (the two-argument form 'test !
> nonempty' is false).  But if $foo has embedded whitespace, it expands to
> more than one word after word-splitting, and you're hosed ('test ! one
> two' can give interesting results, and probably not what you were
> expecting).
>
> You might want to fix your script to just use the safer:
>
> ! test "$foo"
>
> which works even if $foo has embedded whitespace.  That said, you are
> correct that dash should never crash.
>
>>
>> dash crashes.  This occurs both in the version shipped with ubuntu
>> 10.04 and 12.04
>> as well as with dash from git.
>>
>> Here's the stack:
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> __strcmp_sse4_2 () at ../sysdeps/i386/i686/multiarch/strcmp-sse4.S:221
>> 221 ../sysdeps/i386/i686/multiarch/strcmp-sse4.S: No such file or directory.
>> (gdb) bt
>> #0  __strcmp_sse4_2 () at ../sysdeps/i386/i686/multiarch/strcmp-sse4.S:221
>> #1  0x0805938a in getop (s=0x202b <Address 0x202b out of bounds>) at
>> bltin/test.c:168
>> #2  0x08059c91 in t_lex (tp=0x806581c) at bltin/test.c:431
>> #3  0x080595cb in aexpr (n=UNOT) at bltin/test.c:260
>> #4  0x08059557 in oexpr (n=UNOT) at bltin/test.c:243
>> #5  0x080594ba in testcmd (argc=1, argv=0x8065814) at bltin/test.c:219
>> #6  0x0804c526 in evalbltin (cmd=0x805da1c, argc=2, argv=0x8065810,
>> flags=0) at eval.c:910
>
> and given this part of the stack trace, it looks like you were invoking
> 'test ! word'?  But I was unable to reproduce a crash when I tried
> dash.git, so it would be helpful to know exactly what $foo was in your
> reproducer.
>
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
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