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Date: Wed, 13 Oct 2021 00:29:12 -0700 From: Kees Cook <keescook@...omium.org> To: Len Baker <len.baker@....com> Cc: Li Fei1 <fei1.li@...el.com>, gustavoars@...nel.org, linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] virt: acrn: Prefer array_syze and struct_size over open coded arithmetic On Tue, Oct 12, 2021 at 09:34:29AM +0800, Li Fei1 wrote: > On Mon, Oct 11, 2021 at 12:39:02PM +0200, Len Baker wrote: > > As noted in the "Deprecated Interfaces, Language Features, Attributes, > > and Conventions" documentation [1], size calculations (especially > > multiplication) should not be performed in memory allocator (or similar) > > function arguments due to the risk of them overflowing. This could lead > > to values wrapping around and a smaller allocation being made than the > > caller was expecting. Using those allocations could lead to linear > > overflows of heap memory and other misbehaviors. > > > > So, use the array_size() helper to do the arithmetic instead of the > > argument "count * size" in the vzalloc() function. > > > > Also, take the opportunity to add a flexible array member of struct > > vm_memory_region_op to the vm_memory_region_batch structure. And then, > > change the code accordingly and use the struct_size() helper to do the > > arithmetic instead of the argument "size + size * count" in the kzalloc > > function. > > > > This code was detected with the help of Coccinelle and audited and fixed > > manually. > > > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > > > Signed-off-by: Len Baker <len.baker@....com> > > Hi Baker > > Thanks for helping us to fix this issue. This patch looks good to me. > Please add Signed-off-by: Fei Li <fei1.li@...el.com>. > Only two minor comments. For v2, please fix the Subject typo, too. :) "syze" -> "size". -Kees -- Kees Cook
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