Re: [PATCH] - Fix wrong check in aux_syscalls.stp:_struct_sockaddr_u_impl (related to PR16718)

[David Smith <dsmith at redhat dot com>]

On 03/18/2014 07:15 AM, Robin Hack wrote:
> Hi.
> 
> This small patch according to PR16718 fixes wrong check of STAP_ARG_len argument.

I had thought of doing something like this, but figured the new
_stp_copy_from_user() check would work here. I didn't see any harm in
your patch though, so I checked it in.

I then thought about it some more. Your patch did this:

-    size_t len = STAP_ARG_len < 128 ? STAP_ARG_len: 128;
+    size_t len = max(128, STAP_ARG_len);

Depending on when the conversion from signed to unsigned happens, -1 is
still less than 128. So, in commit 0a01aa9 I tightened that up to:

    size_t len = clamp((size_t)STAP_ARG_len, (size_t)0, (size_t)128);

This way we're sure that the value is between 0 and 128. I also went
through the rest of the calls to _stp_copy_from_user(), making sure the
input length was reasonable.

Thanks for the patch.

-- 
David Smith
dsmith@redhat.com
Red Hat
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