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SubjectRe: [PATCH] riscv: Return -EFAULT if copy_to_user() failed in signal.c
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On 02/03/2021 07:28, Tiezhu Yang wrote:
> copy_to_user() returns the amount left to copy, it should return -EFAULT
> if copy to user failed.

This looks technically correct, but the caller (only one)
will check for non-zero and will covert that to -EFAULT
in setup_rt_frame().

I expect if this change is done, it also needs to be done
for the callers too and there's a few others than assume
!=0 is an error.

I think it would be easier to define save_fp_state() to
return non-zero on error and note it does not return an
error code. It may be worth exiting the functio nif
the first __copy_to_user fails?

Note: setup_rt_frame -> setup_sigcontext -> save_fp_frame

>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
> arch/riscv/kernel/signal.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
> index 65942b3..2238fc5 100644
> --- a/arch/riscv/kernel/signal.c
> +++ b/arch/riscv/kernel/signal.c
> @@ -67,7 +67,7 @@ static long save_fp_state(struct pt_regs *regs,
> fstate_save(current, regs);
> err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
> if (unlikely(err))
> - return err;
> + return -EFAULT;
>
> /* We support no other extension state at this time. */
> for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
> @@ -140,8 +140,12 @@ static long setup_sigcontext(struct rt_sigframe __user *frame,
> {
> struct sigcontext __user *sc = &frame->uc.uc_mcontext;
> long err;
> +
> /* sc_regs is structured the same as the start of pt_regs */
> err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
> + if (unlikely(err))
> + return -EFAULT;
> +
> /* Save the floating-point state. */
> if (has_fpu)
> err |= save_fp_state(regs, &sc->sc_fpregs);
>


--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius

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