Re: [Qemu-devel] [PATCH] readline: don't free completions in readline_free()

[Philippe Mathieu-Daudé]

On 01/18/2018 07:45 AM, Paolo Bonzini wrote:
> On 18/01/2018 11:41, Greg Kurz wrote:
>> Since commit e5dc1a6c6c43, QEMU aborts on exit if completion was used
>> in the monitor:
>>
>> *** Error in `obj/ppc64-softmmu/qemu-system-ppc64': double free or
>>  corruption (fasttop): 0x00000100331069d0 ***
>>
>> #0  0x00007ffff267eff0 in raise () from /lib64/libc.so.6
>> #1  0x00007ffff268136c in abort () from /lib64/libc.so.6
>> #2  0x00007ffff26c6b48 in __libc_message () from /lib64/libc.so.6
>> #3  0x00007ffff26d69fc in free () from /lib64/libc.so.6
>> #4  0x00007ffff28cb794 in g_free () from /lib64/libglib-2.0.so.0
>> #5  0x00000000106230e4 in readline_free (rs=0x11223e60) at
>>  /home/greg/Work/qemu/qemu-spapr/util/readline.c:514
>> #6  0x0000000010074cc4 in monitor_data_destroy (mon=0x1121c9f0) at
>>  /home/greg/Work/qemu/qemu-spapr/monitor.c:586
>> #7  0x000000001007bcc8 in monitor_cleanup () at
>>  /home/greg/Work/qemu/qemu-spapr/monitor.c:4125
>> #8  0x0000000010291274 in main (argc=<optimized out>,
>>  argv=<optimized out>, envp=<optimized out>) at
>>  /home/greg/Work/qemu/qemu-spapr/vl.c:4795
>>
>> Completion strings are not persistent accross completions (why would
>> they?). They are allocated under readline_completion(), which already
>> takes care of freeing them before returning.

Oops I missed that.

>>
>> Maybe all completion related bits should be moved out of ReadLineState
>> to a dedicated structure ?
>>
>> In the meantime, let's drop the offending lines from readline_free()
>> to fix the crash.
>>
>> Signed-off-by: Greg Kurz <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

>> ---
>>  util/readline.c |    3 ---
>>  1 file changed, 3 deletions(-)
>>
>> diff --git a/util/readline.c b/util/readline.c
>> index 24ec839854cf..ec91ee0fea6f 100644
>> --- a/util/readline.c
>> +++ b/util/readline.c
>> @@ -510,9 +510,6 @@ void readline_free(ReadLineState *rs)
>>      for (i = 0; i < READLINE_MAX_CMDS; i++) {
>>          g_free(rs->history[i]);
>>      }
>> -    for (i = 0; i < READLINE_MAX_COMPLETIONS; i++) {
>> -        g_free(rs->completions[i]);
>> -    }
>>      g_free(rs);
>>  }
>>  
>>
> 
> Queued, thanks.
> 
> Paolo
>