On Sat, Mar 30, 2024 at 03:32:59PM +0100, Erick Archer wrote:
> This is an effort to get rid of all multiplications from allocation
> functions in order to prevent integer overflows [1][2].
>
> As the "box" variable is a pointer to "struct intel_uncore_box" and
> this structure ends in a flexible array:
>
> struct intel_uncore_box {
> [...]
> struct intel_uncore_extra_reg shared_regs[];
> };
>
> the preferred way in the kernel is to use the struct_size() helper to
> do the arithmetic instead of the calculation "size + count * size" in
> the kzalloc_node() function.
>
> This way, the code is more readable and safer.
>
> This code was detected with the help of Coccinelle, and audited and
> modified manually.
>
> Link:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
> [1]
> Link: https://github.com/KSPP/linux/issues/160 [2]
> Signed-off-by: Erick Archer <erick.arc...@outlook.com>
> ---
> Hi,
>
> The Coccinelle script used to detect this code pattern is the following:
>
> virtual report
>
> @rule1@
> type t1;
> type t2;
> identifier i0;
> identifier i1;
> identifier i2;
> identifier ALLOC =~
> "kmalloc|kzalloc|kmalloc_node|kzalloc_node|vmalloc|vzalloc|kvmalloc|kvzalloc";
> position p1;
> @@
>
> i0 = sizeof(t1) + sizeof(t2) * i1;
> ...
> i2 = ALLOC@p1(..., i0, ...);
>
> @script:python depends on report@
> p1 << rule1.p1;
> @@
>
> msg = "WARNING: verify allocation on line %s" % (p1[0].line)
> coccilib.report.print_report(p1[0],msg)
>
> Regards,
> Erick
> ---
> arch/x86/events/intel/uncore.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 258e2cdf28fa..ce756d24c370 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -350,12 +350,11 @@ static void uncore_pmu_init_hrtimer(struct
> intel_uncore_box *box)
> static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type
> *type,
> int node)
> {
> - int i, size, numshared = type->num_shared_regs ;
> + int i, numshared = type->num_shared_regs;
> struct intel_uncore_box *box;
>
> - size = sizeof(*box) + numshared * sizeof(struct intel_uncore_extra_reg);
> -
> - box = kzalloc_node(size, GFP_KERNEL, node);
> + box = kzalloc_node(struct_size(box, shared_regs, numshared), GFP_KERNEL,
> + node);
> if (!box)
> return NULL;
Thanks, yes, this looks correct to me.
Reviewed-by: Kees Cook <keesc...@chromium.org>
Peter and Ingo, you seem to traditionally take these changes (via -tip)?
Can you please pick this up?
--
Kees Cook
