linux-hardening - Re: [PATCH v3 0/3] Assorted improvements to usercopy

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Date:   Mon, 13 Dec 2021 19:18:57 +0000
From:   William Kucharski <william.kucharski@...cle.com>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
CC:     Kees Cook <keescook@...omium.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH v3 0/3] Assorted improvements to usercopy

I like these, but a quick question:

Since the usercopy_abort() calls are all because the offset exceeds the page
size, is there a reason why you don't specifically state that via the detail
parameter rather than just supply a NULL pointer?

Otherwise for the patch series:

Reviewed-by: William Kucharski <william.kucharski@...cle.com>

> On Dec 13, 2021, at 7:27 AM, Matthew Wilcox (Oracle) <willy@...radead.org> wrote:
> 
> We must prohibit page boundary crossing for kmap() addresses.
> vmap() addresses are limited by the length of the mapping, and
> compound pages are limited by the size of the page.
> 
> These should probably all have test cases?
> 
> v3:
> - Remove a now-unused variable
> v2:
> - Prevent a NULL pointer dereference when a vmalloc-range pointer
>   doesn't have an associated allocation (me)
> - Report better offsets than "0" (Kees)
> 
> 
> Matthew Wilcox (Oracle) (3):
>  mm/usercopy: Check kmap addresses properly
>  mm/usercopy: Detect vmalloc overruns
>  mm/usercopy: Detect compound page overruns
> 
> arch/x86/include/asm/highmem.h   |  1 +
> include/linux/highmem-internal.h | 10 ++++++++
> mm/usercopy.c                    | 43 +++++++++++++++++++++++---------
> 3 files changed, 42 insertions(+), 12 deletions(-)
> 
> -- 
> 2.33.0