From: Oleg Nesterov <oleg@redhat.com>
To: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: David Laight <David.Laight@aculab.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Arnd Bergmann <arnd@arndb.de>, "dbueso@suse.de" <dbueso@suse.de>,
"axboe@kernel.dk" <axboe@kernel.dk>,
Davidlohr Bueso <dave@stgolabs.net>, Eric Wong <e@80x24.org>,
Jason Baron <jbaron@akamai.com>,
Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
linux-aio <linux-aio@kvack.org>,
Omar Kilani <omar.kilani@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()
Date: Wed, 29 May 2019 18:57:18 +0200 [thread overview]
Message-ID: <20190529165717.GC27659@redhat.com> (raw)
In-Reply-To: <CABeXuvouBzZuNarmNcd9JgZgvonL1N_p21gat=O_x0-1hMx=6A@mail.gmail.com>
On 05/28, Deepa Dinamani wrote:
>
> I agree that signal handller being called and return value not being
> altered is an issue with other syscalls also. I was just wondering if
> some userspace code assumption would be assuming this. This is not a
> kernel bug.
>
> But, I do not think we have an understanding of what was wrong in
> 854a6ed56839a anymore since you pointed out that my assumption was not
> correct that the signal handler being called without errno being set
> is wrong.
Deepa, sorry, I simply can't parse the above... most probably because of
my bad English.
> One open question: this part of epoll_pwait was already broken before
> 854a6ed56839a. Do you agree?
>
> if (err == -EINTR) {
> memcpy(¤t->saved_sigmask, &sigsaved,
> sizeof(sigsaved));
> set_restore_sigmask();
> } else
> set_current_blocked(&sigsaved);
I do not understand why do you think this part was broken :/
> Or, I could revert the signal_pending() check and provide a fix
> something like below(not a complete patch)
...
> -void restore_user_sigmask(const void __user *usigmask, sigset_t *sigsaved)
> +int restore_user_sigmask(const void __user *usigmask, sigset_t
> *sigsaved, int sig_pending)
> {
>
> if (!usigmask)
> return;
>
> /*
> * When signals are pending, do not restore them here.
> * Restoring sigmask here can lead to delivering signals that the above
> * syscalls are intended to block because of the sigmask passed in.
> */
> + if (sig_pending) {
> current->saved_sigmask = *sigsaved;
> set_restore_sigmask();
> return;
> }
>
> @@ -2330,7 +2330,8 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct
> epoll_event __user *, events,
>
> error = do_epoll_wait(epfd, events, maxevents, timeout);
>
> - restore_user_sigmask(sigmask, &sigsaved);
> + signal_detected = restore_user_sigmask(sigmask, &sigsaved,
> error == -EINTR);
I fail to understand this pseudo-code, sorry. In particular, do not understand
why restore_user_sigmask() needs to return a boolean.
The only thing I _seem to_ understand is the "sig_pending" flag passed by the
caller which replaces the signal_pending() check. Yes, this is what I think we
should do, and this is what I tried to propose from the very beginning in my
1st email in this thread.
Oleg.
next prev parent reply other threads:[~2019-05-29 16:57 UTC|newest]
Thread overview: 95+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 3:21 [PATCH v2] signal: Adjust error codes according to restore_user_sigmask() Deepa Dinamani
2019-05-22 15:05 ` Oleg Nesterov
2019-05-22 15:55 ` Deepa Dinamani
2019-05-22 16:14 ` Oleg Nesterov
2019-05-22 16:33 ` Deepa Dinamani
2019-05-23 9:03 ` David Laight
2019-05-23 14:59 ` Oleg Nesterov
2019-05-23 16:18 ` David Laight
2019-05-23 16:36 ` Oleg Nesterov
2019-05-23 16:56 ` David Laight
2019-05-23 18:06 ` Deepa Dinamani
2019-05-23 20:41 ` Deepa Dinamani
2019-05-23 21:06 ` Deepa Dinamani
2019-05-24 9:58 ` David Laight
2019-05-24 14:10 ` Oleg Nesterov
2019-05-24 15:16 ` Deepa Dinamani
2019-05-24 16:33 ` Oleg Nesterov
2019-05-24 17:01 ` Deepa Dinamani
2019-05-27 15:04 ` Oleg Nesterov
2019-05-28 20:47 ` Deepa Dinamani
2019-05-29 16:57 ` Oleg Nesterov [this message]
2019-05-29 18:42 ` Deepa Dinamani
2019-05-28 9:02 ` David Laight
2019-05-28 9:12 ` David Laight
2019-05-28 11:37 ` Deepa Dinamani
2019-05-28 12:04 ` David Laight
2019-05-24 14:19 ` Oleg Nesterov
2019-05-24 14:29 ` Deepa Dinamani
2019-05-24 14:51 ` Oleg Nesterov
2019-05-24 13:29 ` Oleg Nesterov
2019-05-24 14:59 ` David Laight
2019-05-24 15:09 ` David Laight
2019-05-24 15:46 ` Oleg Nesterov
2019-05-24 15:44 ` Oleg Nesterov
2019-05-24 16:40 ` David Laight
2019-05-23 14:33 ` Oleg Nesterov
2019-05-22 22:18 ` Chris Down
2019-05-22 22:52 ` Deepa Dinamani
2019-05-29 16:11 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Oleg Nesterov
2019-05-29 16:54 ` David Laight
2019-05-29 18:50 ` Eric Wong
2019-05-30 9:34 ` David Laight
2019-05-30 13:04 ` pselect/etc semantics Eric W. Biederman
2019-05-29 16:56 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Deepa Dinamani
2019-05-29 18:26 ` Deepa Dinamani
2019-05-29 22:32 ` Arnd Bergmann
2019-05-30 1:54 ` pselect/etc semantics Eric W. Biederman
2019-05-30 18:28 ` Arnd Bergmann
2019-05-30 14:40 ` pselect/etc semantics (Was: [PATCH v2] signal: Adjust error codes according to restore_user_sigmask()) Oleg Nesterov
2019-05-30 18:37 ` Arnd Bergmann
2019-05-30 13:01 ` pselect/etc semantics Eric W. Biederman
2019-05-30 15:18 ` David Laight
2019-05-30 16:13 ` Oleg Nesterov
2019-05-30 15:38 ` Eric W. Biederman
2019-05-30 15:48 ` Deepa Dinamani
2019-05-30 16:59 ` Deepa Dinamani
2019-05-30 16:08 ` Oleg Nesterov
2019-05-30 17:20 ` Eric W. Biederman
2019-05-30 16:22 ` David Laight
2019-05-30 15:57 ` Oleg Nesterov
2019-05-30 21:03 ` Eric Wong
2019-06-04 13:41 ` [PATCH] signal: remove the wrong signal_pending() check in restore_user_sigmask() Oleg Nesterov
2019-06-04 15:31 ` Eric W. Biederman
2019-06-04 15:57 ` David Laight
2019-06-04 16:37 ` Arnd Bergmann
2019-06-04 18:14 ` Deepa Dinamani
2019-06-04 18:35 ` Eric Wong
2019-06-04 21:26 ` Linus Torvalds
2019-06-04 22:24 ` Eric Wong
2019-06-04 23:51 ` Eric W. Biederman
2019-06-05 9:04 ` Oleg Nesterov
2019-06-05 8:56 ` Oleg Nesterov
2019-06-05 9:02 ` David Laight
2019-06-05 9:25 ` Oleg Nesterov
2019-06-05 9:58 ` David Laight
2019-06-05 15:58 ` [PATCH -mm 0/1] signal: simplify set_user_sigmask/restore_user_sigmask Oleg Nesterov
2019-06-05 15:58 ` [PATCH -mm 1/1] " Oleg Nesterov
2019-06-06 0:14 ` kbuild test robot
2019-06-06 1:06 ` kbuild test robot
2019-06-06 7:25 ` Oleg Nesterov
2019-06-06 7:30 ` Sedat Dilek
2019-06-05 17:24 ` [PATCH -mm 0/1] " Linus Torvalds
2019-06-06 9:05 ` David Laight
2019-06-06 11:05 ` Oleg Nesterov
2019-06-06 11:29 ` David Laight
2019-06-06 12:41 ` Oleg Nesterov
2019-06-06 13:23 ` David Laight
2019-06-06 10:22 ` Oleg Nesterov
2019-06-06 11:32 ` [PATCH -mm V2 1/1] " Oleg Nesterov
2019-06-06 14:08 ` [PATCH 0/2] select: simplify the usage of restore_saved_sigmask_unless() Oleg Nesterov
2019-06-06 14:08 ` [PATCH 1/2] select: change do_poll() to return -ERESTARTNOHAND rather than -EINTR Oleg Nesterov
2019-06-07 18:05 ` Linus Torvalds
2019-06-06 14:09 ` [PATCH 2/2] select: shift restore_saved_sigmask_unless() into poll_select_copy_remaining() Oleg Nesterov
2019-06-07 21:39 ` [RFC PATCH 0/5]: Removing saved_sigmask Eric W. Biederman
2019-06-11 18:58 ` Oleg Nesterov
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