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 <[email protected]>
---
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;
--
2.25.1
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 <[email protected]>
> ---
> 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 <[email protected]>
Peter and Ingo, you seem to traditionally take these changes (via -tip)?
Can you please pick this up?
--
Kees Cook
On Mon, Apr 29, 2024 at 10:18:03AM -0700, Kees Cook wrote:
> Peter and Ingo, you seem to traditionally take these changes (via -tip)?
> Can you please pick this up?
I have been explicitly not taking these things for perf and sched for a
while now. As I wrote in that other mail, I detest struct_size(), it
obfuscates code for no real benefit afaict.