From: ebiederm@xmission.com (Eric W. Biederman)
To: Arnd Bergmann <arnd@arndb.de>
Cc: Oleg Nesterov <oleg@redhat.com>,
Deepa Dinamani <deepa.kernel@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
dbueso@suse.de, Jens Axboe <axboe@kernel.dk>,
Davidlohr Bueso <dave@stgolabs.net>,
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@gmail.com, Thomas Gleixner <tglx@linutronix.de>,
"# 3.4.x" <stable@vger.kernel.org>
Subject: Re: pselect/etc semantics
Date: Wed, 29 May 2019 20:54:09 -0500 [thread overview]
Message-ID: <874l5czozi.fsf@xmission.com> (raw)
In-Reply-To: <CAK8P3a1fsrz6kAB1z-mqcaNvXL4Hf3XMiN=Q5rzAJ3rLGPK_Yg@mail.gmail.com> (Arnd Bergmann's message of "Thu, 30 May 2019 00:32:32 +0200")
Arnd Bergmann <arnd@arndb.de> writes:
> On Wed, May 29, 2019 at 6:12 PM Oleg Nesterov <oleg@redhat.com> wrote:
>>
>> Al, Linus, Eric, please help.
>>
>> The previous discussion was very confusing, we simply can not understand each
>> other.
>>
>> To me everything looks very simple and clear, but perhaps I missed something
>> obvious? Please correct me.
>
> Thanks for the elaborate explanation in this patch, it all starts making sense
> to me now. I also looked at your patch in detail and thought I had found
> a few mistakes at first but those all turned out to be mistakes in my reading.
>
>> See the compile-tested patch at the end. Of course, the new _xxx() helpers
>> should be renamed somehow. fs/aio.c doesn't look right with or without this
>> patch, but iiuc this is what it did before 854a6ed56839a.
>
> I think this is a nice simplification, but it would help not to mix up the
> minimal regression fix with the rewrite of those functions. For the stable
> kernels, I think we want just the addition of the 'bool interrupted' argument
> to restore_user_sigmask() to close the race that was introduced
> 854a6ed56839a. Following up on that for future kernels, your patch
> improves the readability, but we can probably take it even further.
>
>> - ret = set_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
>> + ret = set_xxx(ksig.sigmask, ksig.sigsetsize);
>> if (ret)
>> return ret;
>>
>> ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
>> - restore_user_sigmask(ksig.sigmask, &sigsaved);
>> - if (signal_pending(current) && !ret)
>> +
>> + interrupted = signal_pending(current);
>> + update_xxx(interrupted);
>
> Maybe name this
>
> restore_saved_sigmask_if(!interrupted);
>
> and make restore_saved_sigmask_if() an inline function
> next to restore_saved_sigmask()?
>
>> @@ -2201,13 +2205,15 @@ COMPAT_SYSCALL_DEFINE6(io_pgetevents,
>> if (usig && copy_from_user(&ksig, usig, sizeof(ksig)))
>> return -EFAULT;
>>
>> - ret = set_compat_user_sigmask(ksig.sigmask, &ksigmask, &sigsaved, ksig.sigsetsize);
>> + ret = set_compat_xxx(ksig.sigmask, ksig.sigsetsize);
>> if (ret)
>> return ret;
>
> With some of the recent discussions about compat syscall handling,
> I now think that we want to just fold set_compat_user_sigmask()
> into set_user_sigmask() (whatever they get called in the end)
> with an in_compat_syscall() conditional inside it, and completely get
> rid of the COMPAT_SYSCALL_DEFINEx() definitions for those
> system calls for which this is the only difference.
>
> Unfortunately we still need the time32/time64 distinction, but removing
> syscall handlers is a significant cleanup here already, and we can
> move most of the function body of sys_io_pgetevents() into
> do_io_getevents() in the process. Same for some of the other calls.
>
> Not sure about the order of the cleanups, but probably something like
> this would work:
>
> 1. fix the race (to be backported)
> 2. unify set_compat_user_sigmask/set_user_sigmask
> 3. remove unneeded compat handlers
> 4. replace restore_user_sigmask with restore_saved_sigmask_if()
> 5. also unify compat_get_fd_set()/get_fd_set() and kill off
> compat select() variants.
Are new system calls added preventing a revert of the patch in question
for stable kernels?
Eric
next prev parent reply other threads:[~2019-05-30 1:54 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
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 ` Eric W. Biederman [this message]
2019-05-30 18:28 ` pselect/etc semantics 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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