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From: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: "Jason A . Donenfeld"
	<Jason-OnJsPKxuuEcAvxtiuMwx3w@public.gmane.org>,
	linux-btrfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Jarkko Sakkinen
	<jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	dsterba-AlSwsSmVLrQ@public.gmane.org,
	David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	linux-sctp-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-stm32-XDFAJ8BFU24N7RejjzZ/Li2xQDfSxrLKVpNB7YpNyf8@public.gmane.org,
	devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org,
	linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	James Morris <jmorris-gx6/JNMH7DfYtjvyW6yDsg@public.gmane.org>,
	kasan-dev-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org,
	linux-wpan-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Dan Carpenter
	<dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	"Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org>,
	linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	ecryptfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-fscrypt-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	linux-amlogic-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	linux-integrity-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linus
Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive()
Date: Wed, 17 Jun 2020 04:08:20 -0700	[thread overview]
Message-ID: <20200617110820.GG8681@bombadil.infradead.org> (raw)
In-Reply-To: <20200617071212.GJ9499-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>

On Wed, Jun 17, 2020 at 09:12:12AM +0200, Michal Hocko wrote:
> On Tue 16-06-20 17:37:11, Matthew Wilcox wrote:
> > Not just performance critical, but correctness critical.  Since kvfree()
> > may allocate from the vmalloc allocator, I really think that kvfree()
> > should assert that it's !in_atomic().  Otherwise we can get into trouble
> > if we end up calling vfree() and have to take the mutex.
> 
> FWIW __vfree already checks for atomic context and put the work into a
> deferred context. So this should be safe. It should be used as a last
> resort, though.

Actually, it only checks for in_interrupt().  If you call vfree() under
a spinlock, you're in trouble.  in_atomic() only knows if we hold a
spinlock for CONFIG_PREEMPT, so it's not safe to check for in_atomic()
in __vfree().  So we need the warning in order that preempt people can
tell those without that there is a bug here.

  parent reply	other threads:[~2020-06-17 11:08 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-16  1:57 [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
2020-06-16  1:57 ` [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree() Waiman Long
2020-06-16  3:30   ` Eric Biggers
2020-06-16 13:05     ` Waiman Long
2020-06-16 15:46     ` David Howells
2020-06-16  6:42   ` Michal Hocko
     [not found]     ` <20200616064208.GA9499-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-06-16  9:08       ` Dan Carpenter
     [not found] ` <20200616015718.7812-1-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2020-06-16  1:57   ` [PATCH v4 2/3] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
     [not found]     ` <20200616015718.7812-3-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2020-06-16 14:26       ` Dan Carpenter
2020-06-16 15:05         ` Waiman Long
2020-06-16  1:57   ` [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info() Waiman Long
2020-06-16 14:48     ` David Sterba
2020-06-16 15:05       ` Waiman Long
2020-06-16 18:53   ` [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Joe Perches
2020-06-16 19:43     ` Waiman Long
     [not found]     ` <fe3b9a437be4aeab3bac68f04193cb6daaa5bee4.camel-6d6DIl74uiNBDgjK7y7TUQ@public.gmane.org>
2020-06-16 19:46       ` Jason A. Donenfeld
2020-06-16 21:14       ` Matthew Wilcox
2020-06-17 21:31       ` Denis Efremov
2020-06-17 23:12         ` Joe Perches
2020-06-16 20:01     ` Waiman Long
2020-06-16 23:01     ` David Sterba
     [not found]       ` <20200616230130.GJ27795-1ReQVI26iDCaZKY3DrU6dA@public.gmane.org>
2020-06-17  0:37         ` Matthew Wilcox
2020-06-17  7:12           ` Michal Hocko
     [not found]             ` <20200617071212.GJ9499-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-06-17 11:08               ` Matthew Wilcox [this message]
     [not found]                 ` <20200617110820.GG8681-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2020-06-17 11:31                   ` Michal Hocko
     [not found]                     ` <20200617113157.GM9499-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2020-06-17 12:23                       ` Matthew Wilcox
     [not found]                         ` <20200617122321.GJ8681-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org>
2020-06-17 12:55                           ` Michal Hocko
2020-06-17  8:03           ` Jo -l

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