linux-kernel - Re: [PATCH 3/6] kernel: split syscall restart from signal handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20201008142135.GH9995@redhat.com>
Date:   Thu, 8 Oct 2020 16:21:35 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de
Subject: Re: [PATCH 3/6] kernel: split syscall restart from signal handling

On 10/05, Jens Axboe wrote:
>
> Move the restart syscall logic into a separate generic entry helper,
> and handle that part separately from signal checking and delivery.
>
> This is in preparation for being able to do syscall restarting
> independently from handling signals.
>
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> ---
>  arch/x86/kernel/signal.c     | 32 ++++++++++++++++++--------------
>  include/linux/entry-common.h | 14 ++++++++++++--
>  kernel/entry/common.c        | 11 ++++++++---
>  3 files changed, 38 insertions(+), 19 deletions(-)

Can't we avoid this patch and the and simplify the change in
exit_to_user_mode_loop() from the next patch? Can't the much more simple
patch below work?

Then later we can even change arch_do_signal() to accept the additional
argument, ti_work, so that it can use ti_work & TIF_NOTIFY_SIGNAL/SIGPENDING
instead of test_thread_flag/task_sigpending.

Oleg.

--- x/arch/x86/kernel/signal.c
+++ x/arch/x86/kernel/signal.c
@@ -808,7 +808,10 @@ void arch_do_signal(struct pt_regs *regs
 {
 	struct ksignal ksig;
 
-	if (get_signal(&ksig)) {
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+		tracehook_notify_signal();
+
+	if (task_sigpending(current) && get_signal(&ksig)) {
 		/* Whee! Actually deliver the signal.  */
 		handle_signal(&ksig, regs);
 		return;
--- x/kernel/entry/common.c
+++ x/kernel/entry/common.c
@@ -155,7 +155,7 @@ static unsigned long exit_to_user_mode_l
 		if (ti_work & _TIF_PATCH_PENDING)
 			klp_update_patch_state(current);
 
-		if (ti_work & _TIF_SIGPENDING)
+		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)
 			arch_do_signal(regs);
 
 		if (ti_work & _TIF_NOTIFY_RESUME) {