Date: Tue, 13 Mar 2018 18:19:51 +0100 (CET) From: Julia Lawall <julia.lawall@...6.fr> To: Matthew Wilcox <willy@...radead.org> cc: Julia Lawall <julia.lawall@...6.fr>, Kees Cook <keescook@...omium.org>, Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <mawilcox@...rosoft.com>, Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, cocci@...teme.lip6.fr, Himanshu Jha <himanshujha199640@...il.com> Subject: Re: [PATCH 2/2] mm: Add kvmalloc_ab_c and kvzalloc_struct On Thu, 8 Mar 2018, Matthew Wilcox wrote: > On Thu, Mar 08, 2018 at 07:24:47AM +0100, Julia Lawall wrote: > > On Wed, 7 Mar 2018, Matthew Wilcox wrote: > > > On Wed, Mar 07, 2018 at 10:18:21PM +0100, Julia Lawall wrote: > > > > > Otherwise, yes, please. We could build a coccinelle rule for > > > > > additional replacements... > > > > > > > > A potential semantic patch and the changes it generates are attached > > > > below. Himanshu Jha helped with its development. Working on this > > > > uncovered one bug, where the allocated array is too large, because the > > > > size provided for it was a structure size, but actually only pointers to > > > > that structure were to be stored in it. > > > > > > This is cool! Thanks for doing the coccinelle patch! Diffstat: > > > > > > 50 files changed, 81 insertions(+), 124 deletions(-) > > > > > > I find that pretty compelling. I'll repost the kvmalloc_struct patch > > > imminently. > > > > Thanks. So it's OK to replace kmalloc and kzalloc, even though they > > didn't previously consider vmalloc and even though kmalloc doesn't zero? > > We'll also need to replace the corresponding places where those structs > are freed with kvfree(). Can coccinelle handle that too? Is the use of vmalloc a necessary part of the design? Or could there be a non vmalloc versions for call sites that are already ok with that? julia > > There are a few other cases that use GFP_NOFS and GFP_NOWAIT, but I didn't > > transform those because the comment says that the flags should be > > GFP_KERNEL based. Should those be transformed too? > > The problem with non-GFP_KERNEL allocations is that vmalloc may have to > allocate page tables, which is always done with an implicit GFP_KERNEL > allocation. There's an intent to get rid of GFP_NOFS, but that's not > been realised yet (and I'm not sure of our strategy to eliminate it ... > I'll send a separate email about that). I'm not sure why anything's > trying to allocate with GFP_NOWAIT; can you send a list of those places? >
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