Re: [PATCH 04/18] mm, aout: handle vm_brk failures

[Vlastimil Babka]

On 02/29/2016 02:26 PM, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> vm_brk is allowed to fail but load_aout_binary simply ignores the error
> and happily continues. I haven't noticed any problem from that in real
> life but later patches will make the failure more likely because
> vm_brk will become killable (resp. mmap_sem for write waiting will become
> killable) so we should be more careful now.
>
> The error handling should be quite straightforward because there are
> calls to vm_mmap which check the error properly already. The only
> notable exception is set_brk which is called after beyond_if label.
> But nothing indicates that we cannot move it above set_binfmt as the two
> do not depend on each other and fail before we do set_binfmt and alter
> reference counting.
>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Acked--by: Vlastimil Babka <vbabka@xxxxxxx>

[...]

> @@ -378,7 +381,9 @@ static int load_aout_library(struct file *file)
>   			       "N_TXTOFF is not page aligned. Please convert library: %pD\n",
>   			       file);
>   		}
> -		vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> +		retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> +		if (IS_ERR_VALUE(retval))
> +			goto out;
>   		

You could have removed the extra whitespace on the line above, which my vim so 
prominently highlights :)

>   		read_code(file, start_addr, N_TXTOFF(ex),
>   			  ex.a_text + ex.a_data);