On Wed, May 27, 2015 at 8:27 AM, Jarod Wilson <jwil...@redhat.com> wrote:
> On May 26, 2015, at 5:24 PM, Alexey Dobriyan <adobri...@gmail.com> wrote:
>>
>>> On Tue, May 26, 2015 at 04:42:36PM -0400, Jarod Wilson wrote:
>>>> On 5/8/2015 8:28 AM, Alexey Dobriyan wrote:
>>>> /proc/$PID/cmdline truncates output at PAGE_SIZE. It is easy to see with
>>>>
>>>> $ cat /proc/self/cmdline $(seq 1037) 2>/dev/null
>>>>
>>>> However, command line size was never limited to PAGE_SIZE but to 128 KB and
>>>> relatively recently limitation was removed altogether.
>>>>
>>>> People noticed and ask questions:
>>>> http://stackoverflow.com/questions/199130/how-do-i-increase-the-proc-pid-cmdline-4096-byte-limit
>>>>
>>>> seq file interface is not OK, because it kmalloc's for whole output and
>>>> open + read(, 1) + sleep will pin arbitrary amounts of kernel memory.
>>>> To not do that, limit must be imposed which is incompatible with
>>>> arbitrary sized command lines.
>>>>
>>>> I apologize for hairy code, but this it direct consequence of command line
>>>> layout in memory and hacks to support things like "init [3]".
>>>>
>>>> The loops are "unrolled" otherwise it is either macros which hide
>>>> control flow or functions with 7-8 arguments with equal line count.
>>>>
>>>> There should be real setproctitle(2) or something.
>>>>
>>>> Signed-off-by: Alexey Dobriyan <adobri...@gmail.com>
>>>> Tested-by: Jarod Wilson <ja...@redhat.com>
>>>> Acked-by: Jarod Wilson <ja...@redhat.com>
>>>
>>> Should have tested on more than just x86, it appears. We've started
>>> hammering on this internally across all arches, and its exploded
>>> multiple times on ppc64 now:
>>>
>>> [ 2717.074699] ------------[ cut here ]------------
>>> [ 2717.074787] kernel BUG at fs/proc/base.c:244!
>>
>>> OE-------------- 3.10.0-255.el7.ppc64.debug #1
>>
>> Which BUG_ON is this?
>>
>> BUG_ON(*pos < 0);
>> BUG_ON(arg_start > arg_end);
>> BUG_ON(env_start > env_end);
>
> Ah, sorry, right, might not be exactly the same with the back-up ported
> version... It was the env_start > env_end one.
Patch is OK. Checkpoint/restart people aren't checking syscall input properly:
case PR_SET_MM_ENV_END:
if (!vma) {
error = -EFAULT;
goto out;
}
if (opt == PR_SET_MM_START_STACK)
mm->start_stack = addr;
else if (opt == PR_SET_MM_ARG_START)
mm->arg_start = addr;
else if (opt == PR_SET_MM_ARG_END)
mm->arg_end = addr;
else if (opt == PR_SET_MM_ENV_START)
mm->env_start = addr;
else if (opt == PR_SET_MM_ENV_END)
mm->env_end = addr;
break;
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
