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    SubjectRe: [RFC] coccicheck: add a test for repeat memory fetches


    On Tue, 10 Jan 2017, Kees Cook wrote:

    > On Tue, Jan 10, 2017 at 1:14 PM, Julia Lawall <julia.lawall@lip6.fr> wrote:
    > > OK, I have the impression that what you are looking for is the following,
    > > that currently does not seem to work well. Still maybe it gives an idea.
    > >
    > > The basic pattern is the following sequence:
    > >
    > > 1. copy_from_user
    > > 2. test on a field of the copied value
    > > 3. another copy_from_user
    > > 4. a use of the same field as tested in step 2 from the structure obtained
    > > by the second copy_from_user or a function call with the structure as an
    > > argument
    >
    > This looks pretty good!
    >
    > > In the case where the second copy_from_user stores the result in a
    > > pointer, then a return with no reference of the tested field is also a
    > > concern, unless, the pointer was already kfreed.
    >
    > I think sequence "2" above missing just looking at a direct value,
    > like if instead of a field it was a u32. Also, should binop include
    > "=="?

    I wasn't sure what to do with a direct value, because one wouldn't know
    what field it would correspond to. A solution could be to pull the first
    field out of the structure declaration.

    I'll add == and !=.

    > And we need to add back in get_user() too... hmmm

    OK.

    julia

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