From: Enke Chen <enkechen@cisco.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Khalid Aziz <khalid.aziz@oracle.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Helge Deller <deller@gmx.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <christian@brauner.io>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Roman Gushchin <guro@fb.com>,
Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
Dominik Brodowski <linux@dominikbrodowski.net>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org,
"Victor Kamensky (kamensky)" <kamensky@cisco.com>,
xe-linux-external@cisco.com, Stefan Strogin <sstrogin@cisco.com>,
Enke Chen <enkechen@cisco.com>
Subject: Re: [PATCH v2] kernel/signal: Signal-based pre-coredump notification
Date: Tue, 23 Oct 2018 14:40:10 -0700 [thread overview]
Message-ID: <a7cd5312-f743-cf57-7945-c2964026f652@cisco.com> (raw)
In-Reply-To: <1e68a3ce-32cd-b058-3d1d-36455ceca848@cisco.com>
Hi, Oleg:
On 10/23/18 12:43 PM, Enke Chen wrote:
>>
>>> --- a/fs/coredump.c
>>> +++ b/fs/coredump.c
>>> @@ -546,6 +546,7 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>> struct cred *cred;
>>> int retval = 0;
>>> int ispipe;
>>> + bool notify;
>>> struct files_struct *displaced;
>>> /* require nonrelative corefile path and be extra careful */
>>> bool need_suid_safe = false;
>>> @@ -590,6 +591,15 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>>> if (retval < 0)
>>> goto fail_creds;
>>>
>>> + /*
>>> + * Send the pre-coredump signal to the parent if requested.
>>> + */
>>> + read_lock(&tasklist_lock);
>>> + notify = do_notify_parent_predump(current);
>>> + read_unlock(&tasklist_lock);
>>> + if (notify)
>>> + cond_resched();
>>
>> Hmm. I do not understand why do we need cond_resched(). And even if we need it,
>> why we can't call it unconditionally?
>
> Remember the goal is to allow the parent (e.g., a process manager) to take early
> action. The "yield" before doing coredump will help.
>
> The yield is made conditional because the notification is conditional.
> Is that ok?
Given this is in do_coredump(), it is ok to make it unconditional for simplicity.
>>
>>> +bool do_notify_parent_predump(struct task_struct *tsk)
>>> +{
>>> + struct sighand_struct *sighand;
>>> + struct kernel_siginfo info;
>>> + struct task_struct *parent;
>>> + unsigned long flags;
>>> + pid_t pid;
>>> + int sig;
>>> +
>>> + parent = tsk->parent;
>>> + sighand = parent->sighand;
>>> + pid = task_tgid_vnr(tsk);
>>> +
>>> + spin_lock_irqsave(&sighand->siglock, flags);
>>> + sig = parent->signal->predump_signal;
>>> + if (!valid_predump_signal(sig)) {
>>> + spin_unlock_irqrestore(&sighand->siglock, flags);
>>> + return false;
>>> + }
>>
>> Why do we need to check parent->signal->predump_signal under ->siglock?
>> This complicates the code for no reason, afaics.
Will simplify.
Thanks. -- Enke
next prev parent reply other threads:[~2018-10-23 21:40 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 0:33 [PATCH] kernel/signal: Signal-based pre-coredump notification Enke Chen
2018-10-13 6:40 ` Greg Kroah-Hartman
2018-10-15 18:16 ` Enke Chen
2018-10-15 18:43 ` Greg Kroah-Hartman
2018-10-15 18:49 ` Enke Chen
2018-10-15 18:58 ` Greg Kroah-Hartman
2018-10-13 10:44 ` Christian Brauner
2018-10-15 18:39 ` Enke Chen
2018-10-13 18:27 ` Jann Horn
2018-10-15 18:36 ` Enke Chen
2018-10-15 18:54 ` Jann Horn
2018-10-15 19:23 ` Enke Chen
2018-10-19 23:01 ` Enke Chen
2018-10-22 15:40 ` Jann Horn
2018-10-22 20:48 ` Enke Chen
2018-10-15 12:05 ` Oleg Nesterov
2018-10-15 18:54 ` Enke Chen
2018-10-15 19:17 ` Enke Chen
2018-10-15 19:26 ` Enke Chen
2018-10-16 14:14 ` Oleg Nesterov
2018-10-16 15:09 ` Eric W. Biederman
2018-10-17 0:39 ` Enke Chen
2018-10-15 21:21 ` Alan Cox
2018-10-15 21:31 ` Enke Chen
2018-10-15 23:28 ` Eric W. Biederman
2018-10-16 0:33 ` valdis.kletnieks
2018-10-16 0:54 ` Enke Chen
2018-10-16 15:26 ` Eric W. Biederman
2018-10-22 21:09 ` [PATCH v2] " Enke Chen
2018-10-23 9:23 ` Oleg Nesterov
2018-10-23 19:43 ` Enke Chen
2018-10-23 21:40 ` Enke Chen [this message]
2018-10-24 13:52 ` Oleg Nesterov
2018-10-24 21:56 ` Enke Chen
2018-10-24 5:39 ` [PATCH v3] " Enke Chen
2018-10-24 14:02 ` Oleg Nesterov
2018-10-24 22:02 ` Enke Chen
2018-10-25 22:56 ` [PATCH v4] " Enke Chen
2018-10-26 8:28 ` Oleg Nesterov
2018-10-26 22:23 ` Enke Chen
2018-10-29 11:18 ` Oleg Nesterov
2018-10-29 21:08 ` Enke Chen
2018-10-29 22:31 ` [PATCH v5] " Enke Chen
2018-10-30 16:46 ` Oleg Nesterov
2018-10-31 0:25 ` Enke Chen
2018-11-22 0:37 ` Andrew Morton
2018-11-22 1:09 ` Enke Chen
2018-11-22 1:18 ` Enke Chen
2018-11-22 1:33 ` Andrew Morton
2018-11-22 4:57 ` Enke Chen
2018-11-12 23:22 ` Enke Chen
2018-11-27 22:54 ` [PATCH v5 1/2] " Enke Chen
2018-11-28 15:19 ` Dave Martin
2018-11-29 0:15 ` Enke Chen
2018-11-29 11:55 ` Dave Martin
2018-11-30 0:27 ` Enke Chen
2018-11-30 12:03 ` Oleg Nesterov
2018-12-05 6:47 ` Jann Horn
2018-12-04 22:37 ` Andrew Morton
2018-12-06 17:29 ` Oleg Nesterov
2018-10-25 22:56 ` [PATCH] selftests/prctl: selftest for pre-coredump signal notification Enke Chen
2018-11-27 22:54 ` [PATCH v5 2/2] " Enke Chen
2018-10-24 13:29 ` [PATCH v2] kernel/signal: Signal-based pre-coredump notification Eric W. Biederman
2018-10-24 23:50 ` Enke Chen
2018-10-25 12:23 ` Eric W. Biederman
2018-10-25 20:45 ` Enke Chen
2018-10-25 21:24 ` Enke Chen
2018-10-25 21:56 ` Enke Chen
2018-10-25 13:45 ` Jann Horn
2018-10-25 20:21 ` Eric W. Biederman
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