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

[Paolo Bonzini]

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.
> 
> 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>
> ---
>  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