On 09/09/11 09:52, Andrew Morton wrote:
> On Thu, 08 Sep 2011 10:39:24 +1000
> Ryan Mallon <rmallon@xxxxxxxxx> wrote:
>
>> Replace valid_arg_len function in fs/exec.c with max_arg_len function
>> and pass the correct length to strnlen_user.
>>
>> --- a/fs/exec.c
>> +++ b/fs/exec.c
>> @@ -296,9 +296,9 @@ err:
>> return err;
>> }
>>
>> -static bool valid_arg_len(struct linux_binprm *bprm, long len)
>> +static long max_arg_len(struct linux_binprm *bprm)
>> {
>> - return len <= MAX_ARG_STRLEN;
>> + return MAX_ARG_STRLEN;
>> }
>>
>> #else
>> @@ -354,9 +354,9 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
>> return 0;
>> }
>>
>> -static bool valid_arg_len(struct linux_binprm *bprm, long len)
>> +static long max_arg_len(struct linux_binprm *bprm)
>> {
>> - return len <= bprm->p;
>> + return bprm->p;
>> }
>>
>> #endif /* CONFIG_MMU */
>> @@ -474,18 +474,19 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
>> const char __user *str;
>> int len;
>> unsigned long pos;
>> + long max_len = max_arg_len(bprm);
>>
>> ret = -EFAULT;
>> str = get_user_arg_ptr(argv, argc);
>> if (IS_ERR(str))
>> goto out;
>>
>> - len = strnlen_user(str, MAX_ARG_STRLEN);
>> - if (!len || len > MAX_ARG_STRLEN)
>> + len = strnlen_user(str, max_len);
>> + if (!len)
>> goto out;
>>
>> ret = -E2BIG;
>> - if (!valid_arg_len(bprm, len))
>> + if (len > max_len)
>> goto out;
>>
>> /* We're going to work our way backwords. */
> I'm struggling to find a reason to merge this - it churns code around
> rather pointlessly?
>
That's fine. I originally went looking after a discussion with Mark
about the weird strnlen_user semantics and this usage looked incorrect
to me because it wasn't obviously checking >= MAX_ARG_STRLEN.
The rework I think makes it a bit more clear and passes the correct max
length to strnlen_user. Its a bit odd to pass MAX_ARG_STRLEN and then
check if it is longer than bprm->len, and I guess assumes that bprm->len
is less than MAX_ARG_STRLEN.
Feel free to drop the patch if you think it is just churn.
~Ryan
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