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    SubjectRe: [PATCH 18/20] objtool: Add UACCESS validation
    On Thu, Mar 07, 2019 at 08:03:13PM +0100, Peter Zijlstra wrote:
    > On Thu, Mar 07, 2019 at 07:48:13PM +0100, Peter Zijlstra wrote:
    > > On Thu, Mar 07, 2019 at 09:54:14AM -0800, Linus Torvalds wrote:
    > > > On Thu, Mar 7, 2019 at 9:41 AM Peter Zijlstra <peterz@infradead.org> wrote:
    > > > > >
    > > > > > What's the call site that made you go "just add __memset() to the list"?
    > > > >
    > > > > __asan_{,un}poinson_stack_memory()
    > > > > kasan_{,un}poison_shadow()
    > > > > __memset()
    > > >
    > > > Ugh. I think I almost just agree with your decision to just let that
    > > > memset go unchecked.
    > > >
    > > > I'm not saying it's right, but it doesn't seem to be a fight worth fighting.
    > >
    > > One think I could do; is add a filter to each function and only allow
    > > __memset from the kasan code, and not from anywhere else.
    >
    > Ah.. how about I feed objtool a text file with all these symbol names;
    > and I have Makefile compose file that from fragments.
    >
    > Then only KASAN builds will have memset whitelisted, and any other build
    > will still flag memset abuse.
    >
    > Now I only have to figure out how to make Makefile do something like
    > that :-)

    Instead of adding all those additional moving parts, I would much rather
    either:

    a) have kasan call a special whitelisted version of memset (like hpa
    suggested); or

    b) just don't use the objtool --uaccess flag for KASAN builds.

    --
    Josh

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