[PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive()
willy at infradead.org
Wed Jun 17 13:08:20 CEST 2020
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.
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