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    SubjectRe: RELEASE BLOCKER: Linux doesn't follow x86/x86-64 ABI wrt direction flag
    Olivier Galibert wrote:
    > On Thu, Mar 06, 2008 at 09:58:41AM -0800, Joe Buck wrote:
    >> If the kernel allows state to leak from one process to another,
    >> for example from a process running as root to a process running as an
    >> ordinary user, it's a bug, with possible security implications.
    >
    > I don't think that it is relevant in your case. If you have the
    > signal handler in something that does not share the VM with the
    > interrupted thread, you will have a context switch which is supposed
    > to store the direction flag and restore the one from the handling
    > thread. If you share the VM there is no context switch but you have
    > access to the exact same memory with the exact same rights, making the
    > leak irrelevant.

    A process can send a signal via kill. IOW, a malicious process can
    *control when the process would be interrupted* in order to get it into
    the signal handler with DF=1.

    Paolo


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