* Oleg Nesterov <o...@redhat.com> [2020-07-23 17:44:20]:
> If a tracee is uprobed and it hits int3 inserted by debugger, handle_swbp()
> does send_sig(SIGTRAP, current, 0) which means si_code == SI_USER. This used
> to work when this code was written, but then GDB started to validate si_code
> and now it simply can't use breakpoints if the tracee has an active uprobe:
>
>
> The tracee hits the internal breakpoint inserted by GDB to monitor shared
> library events but GDB misinterprets this SIGTRAP and reports a signal.
>
> Change handle_swbp() to use force_sig(SIGTRAP), this matches do_int3_user()
> and fixes the problem.
>
> This is the minimal fix for -stable, arch/x86/kernel/uprobes.c is equally
> wrong; it should use send_sigtrap(TRAP_TRACE) instead of send_sig(SIGTRAP),
> but this doesn't confuse GDB and needs another x86-specific patch.
>
> Reported-by: Aaron Merey <ame...@redhat.com>
> Cc: sta...@vger.kernel.org
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Looks good to me.
Reviewed-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/events/uprobes.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index bb0862873dba..5f8b0c52fd2e 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -2199,7 +2199,7 @@ static void handle_swbp(struct pt_regs *regs)
> if (!uprobe) {
> if (is_swbp > 0) {
> /* No matching uprobe; signal SIGTRAP. */
> - send_sig(SIGTRAP, current, 0);
> + force_sig(SIGTRAP);
> } else {
> /*
> * Either we raced with uprobe_unregister() or we can't
> --
> 2.25.1.362.g51ebf55
>
>
--
Thanks and Regards
Srikar Dronamraju
