Re: [PATCH 08/21] exec: Fix latent file_ram_alloc() error handling bug

[Igor Mammedov <imammedo@redhat.com>]

On Sat, 30 Nov 2019 20:42:27 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> When os_mem_prealloc() fails, file_ram_alloc() calls qemu_ram_munmap()
> and returns null.  Except it doesn't when its @errp argument is null,
> because it checks for failure with (errp && *errp).  Messed up in
> commit 056b68af77 "fix qemu exit on memory hotplug when allocation
> fails at prealloc time".
> 
> The bug can't bite as no caller actually passes null.  Fix it anyway.
> 
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  exec.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index ffdb518535..45695a5f2d 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1841,6 +1841,7 @@ static void *file_ram_alloc(RAMBlock *block,
>                              bool truncate,
>                              Error **errp)
>  {
> +    Error *err = NULL;
>      MachineState *ms = MACHINE(qdev_get_machine());
>      void *area;
>  
> @@ -1898,8 +1899,9 @@ static void *file_ram_alloc(RAMBlock *block,
>      }
>  
>      if (mem_prealloc) {
> -        os_mem_prealloc(fd, area, memory, ms->smp.cpus, errp);
> -        if (errp && *errp) {
> +        os_mem_prealloc(fd, area, memory, ms->smp.cpus, &err);
> +        if (err) {
> +            error_propagate(errp, err);
>              qemu_ram_munmap(fd, area, memory);
>              return NULL;
>          }