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    SubjectRe: [PATCH v2 13/19] x86/signal: Check if vdso_image_32 is mapped before trying to land on it
    On Mon, Nov 23, 2020 at 4:29 PM Dmitry Safonov <dima@arista.com> wrote:
    >
    > Provide current_has_vdso_image_32() helper and check it apriory landing
    > attempt on vdso vma.
    > The helper is a macro, not a static inline funciton to avoid
    > linux/sched/task_stack.h inclusion in asm/vdso.h.

    Can you make this more general? For example:

    current_has_vdso(&vdso_image_whatever)

    also:

    > diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
    > index 18d8f17f755c..d9ab58cc765b 100644
    > --- a/arch/x86/entry/common.c
    > +++ b/arch/x86/entry/common.c
    > @@ -142,11 +142,16 @@ static noinstr bool __do_fast_syscall_32(struct pt_regs *regs)
    > /* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
    > __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
    > {
    > + unsigned long landing_pad;
    > +
    > + if (!current_has_vdso_image_32())
    > + force_sigsegv(SIGSEGV);

    Falling through seems incorrect here. I would instead write 0 to rip,
    do the force_sigsegv(), and exit, making sure that exiting goes
    through the correct path.

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