Re: [PATCH] signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die

Eric W. Biederman
2021-08-25T15:56:36Z

ebiederm@xmission.com (Eric W. Biederman) writes:

> In the fpsp040 code when copyin or copyout fails call
> force_sigsegv(SIGSEGV) instead of do_exit(SIGSEGV).
>
> This solves a couple of problems. Because do_exit embeds the ptrace
> stop PTRACE_EVENT_EXIT a complete stack frame needs to be present for
> that to work correctly. There is always the information needed for a
> ptrace stop where get_signal is called. So exiting with a signal
> solves the ptrace issue.
>
> Further exiting with a signal ensures that all of the threads in a
> process are killed not just the thread that malfunctioned. Which
> avoids confusing userspace.
>
> To make force_sigsegv(SIGSEGV) work in fpsp040_die modify the code to
> save all of the registers and jump to ret_from_exception (which
> ultimately calls get_signal) after fpsp040_die returns.
>
> v2: Updated the branches to use gas's pseudo ops that automatically
> calculate the best branch instruction to use for the purpose.
>
> v1: Link: https://lkml.kernel.org/r/87a6m8kgtx.fsf_-_@disp2133
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

Any chance I can get an ack on this patch?

Eric

> ---
> arch/m68k/fpsp040/skeleton.S | 3 ++-
> arch/m68k/kernel/traps.c | 2 +-
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/m68k/fpsp040/skeleton.S b/arch/m68k/fpsp040/skeleton.S
> index a8f41615d94a..439395aa6fb4 100644
> --- a/arch/m68k/fpsp040/skeleton.S
> +++ b/arch/m68k/fpsp040/skeleton.S
> @@ -502,7 +502,8 @@ in_ea:
> .section .fixup,#alloc,#execinstr
> .even
> 1:
> - jbra fpsp040_die
> + jbsr fpsp040_die
> + jbra .Lnotkern
>
> .section __ex_table,#alloc
> .align 4
> diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c
> index 9e1261462bcc..5b19fcdcd69e 100644
> --- a/arch/m68k/kernel/traps.c
> +++ b/arch/m68k/kernel/traps.c
> @@ -1150,7 +1150,7 @@ asmlinkage void set_esp0(unsigned long ssp)
> */
> asmlinkage void fpsp040_die(void)
> {
> - do_exit(SIGSEGV);
> + force_sigsegv(SIGSEGV);
> }
>
> #ifdef CONFIG_M68KFPU_EMU