Re: [PATCH v2 1/1] of: reserved_mem: Have kmemleak ignore dynamically allocated reserved mem

[Mike Rapoport <rppt@kernel.org>]

On Wed, Feb 08, 2023 at 03:20:00PM -0800, Isaac J. Manjarres wrote:
> Currently, kmemleak ignores dynamically allocated reserved memory
> regions that don't have a kernel mapping. However, regions that do
> retain a kernel mapping (e.g. CMA regions) do get scanned by kmemleak.
> 
> This is not ideal for two reasons:
> 
> 1. kmemleak works by scanning memory regions for pointers to
> allocated objects to determine if those objects have been leaked
> or not. However, reserved memory regions can be used between drivers
> and peripherals for DMA transfers, and thus, would not contain pointers
> to allocated objects, making it unnecessary for kmemleak to scan
> these reserved memory regions.
> 
> 2. When CONFIG_DEBUG_PAGEALLOC is enabled, along with kmemleak, the
> CMA reserved memory regions are unmapped from the kernel's address
> space when they are freed to buddy at boot. These CMA reserved regions
> are still tracked by kmemleak, however, and when kmemleak attempts to
> scan them, a crash will happen, as accessing the CMA region will result
> in a page-fault, since the regions are unmapped.
> 
> Thus, use kmemleak_ignore_phys() for all dynamically allocated reserved
> memory regions, instead of those that do not have a kernel mapping
> associated with them.
> 
> Cc: <stable@vger.kernel.org>    # 5.15+
> Fixes: a7259df76702 ("memblock: make memblock_find_in_range method private")
> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>

Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  drivers/of/of_reserved_mem.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 65f3b02a0e4e..f90975e00446 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -48,9 +48,10 @@ static int __init early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
>  		err = memblock_mark_nomap(base, size);
>  		if (err)
>  			memblock_phys_free(base, size);
> -		kmemleak_ignore_phys(base);
>  	}
>  
> +	kmemleak_ignore_phys(base);
> +
>  	return err;
>  }
>  
> -- 
> 2.39.1.581.gbfd45094c4-goog
> 

-- 
Sincerely yours,
Mike.