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From: Jason Gunthorpe <jgg@nvidia.com>
To: Jann Horn <jannh@google.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	Jeff Dike <jdike@addtoit.com>,
	linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, "Eric W . Biederman" <ebiederm@xmission.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	John Hubbard <jhubbard@nvidia.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michel Lespinasse <walken@google.com>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>
Subject: Re: [PATCH v2 2/2] exec: Broadly lock nascent mm until setup_arg_pages()
Date: Wed, 7 Oct 2020 09:12:34 -0300	[thread overview]
Message-ID: <20201007121234.GS4734@nvidia.com> (raw)
In-Reply-To: <20201006225450.751742-3-jannh@google.com>

On Wed, Oct 07, 2020 at 12:54:50AM +0200, Jann Horn wrote:
> @@ -1545,6 +1532,18 @@ void setup_new_exec(struct linux_binprm * bprm)
>  	me->mm->task_size = TASK_SIZE;
>  	mutex_unlock(&me->signal->exec_update_mutex);
>  	mutex_unlock(&me->signal->cred_guard_mutex);
> +
> +#ifndef CONFIG_MMU
> +	/*
> +	 * On MMU, setup_arg_pages() wants to access bprm->vma after this point,
> +	 * so we can't drop the mmap lock yet.
> +	 * On !MMU, we have neither setup_arg_pages() nor bprm->vma, so we
> +	 * should drop the lock here.
> +	 */
> +	mmap_write_unlock(bprm->mm);
> +	mmput(bprm->mm);
> +	bprm->mm = NULL;
> +#endif
>  }

It looks like this could this be a

  if (!IS_ENABLED(CONFIG_MMU))

This all seems nice, more locking points were removed than added at
least

Jason

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WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Jann Horn <jannh@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
	<linux-kernel@vger.kernel.org>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Michel Lespinasse <walken@google.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Jeff Dike <jdike@addtoit.com>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	<linux-um@lists.infradead.org>,
	"John Hubbard" <jhubbard@nvidia.com>
Subject: Re: [PATCH v2 2/2] exec: Broadly lock nascent mm until setup_arg_pages()
Date: Wed, 7 Oct 2020 09:12:34 -0300	[thread overview]
Message-ID: <20201007121234.GS4734@nvidia.com> (raw)
In-Reply-To: <20201006225450.751742-3-jannh@google.com>

On Wed, Oct 07, 2020 at 12:54:50AM +0200, Jann Horn wrote:
> @@ -1545,6 +1532,18 @@ void setup_new_exec(struct linux_binprm * bprm)
>  	me->mm->task_size = TASK_SIZE;
>  	mutex_unlock(&me->signal->exec_update_mutex);
>  	mutex_unlock(&me->signal->cred_guard_mutex);
> +
> +#ifndef CONFIG_MMU
> +	/*
> +	 * On MMU, setup_arg_pages() wants to access bprm->vma after this point,
> +	 * so we can't drop the mmap lock yet.
> +	 * On !MMU, we have neither setup_arg_pages() nor bprm->vma, so we
> +	 * should drop the lock here.
> +	 */
> +	mmap_write_unlock(bprm->mm);
> +	mmput(bprm->mm);
> +	bprm->mm = NULL;
> +#endif
>  }

It looks like this could this be a

  if (!IS_ENABLED(CONFIG_MMU))

This all seems nice, more locking points were removed than added at
least

Jason


  reply	other threads:[~2020-10-07 12:12 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-06 22:54 [PATCH v2 0/2] Broad write-locking of nascent mm in execve Jann Horn
2020-10-06 22:54 ` Jann Horn
2020-10-06 22:54 ` [PATCH v2 1/2] mmap locking API: Order lock of nascent mm outside lock of live mm Jann Horn
2020-10-06 22:54   ` Jann Horn
2020-10-07  7:42   ` Johannes Berg
2020-10-07  7:42     ` Johannes Berg
2020-10-07  8:28     ` Jann Horn
2020-10-07  8:28       ` Jann Horn
2020-10-07 11:35       ` Johannes Berg
2020-10-07 11:35         ` Johannes Berg
2020-10-06 22:54 ` [PATCH v2 2/2] exec: Broadly lock nascent mm until setup_arg_pages() Jann Horn
2020-10-06 22:54   ` Jann Horn
2020-10-07 12:12   ` Jason Gunthorpe [this message]
2020-10-07 12:12     ` Jason Gunthorpe

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