Re: kmemleak panic

[Marek Szyprowski]

Hi Mike,

On 2019-01-23 06:54, Mike Rapoport wrote:

...
> Resending it as a formal patch now, I took a liberty to add your Tested-by.
>
> >From a847ca684db29a3c09e4dd2a8a008b35cf36e52f Mon Sep 17 00:00:00 2001
> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Date: Wed, 23 Jan 2019 07:38:50 +0200
> Subject: [PATCH] of: fix kmemleak crash caused by imbalance in early memory
>  reservation
>
> Marc Gonzalez reported the following kmemleak crash:
>
> Unable to handle kernel paging request at virtual address ffffffc021e00000
> Mem abort info:
>   ESR = 0x96000006
>   Exception class = DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
> Data abort info:
>   ISV = 0, ISS = 0x00000006
>   CM = 0, WnR = 0
> swapper pgtable: 4k pages, 39-bit VAs, pgdp = (____ptrval____)
> [ffffffc021e00000] pgd=000000017e3ba803, pud=000000017e3ba803,
> pmd=0000000000000000
> Internal error: Oops: 96000006 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 6 PID: 523 Comm: kmemleak Tainted: G S      W         5.0.0-rc1 #13
> Hardware name: Qualcomm Technologies, Inc. MSM8998 v1 MTP (DT)
> pstate: 80000085 (Nzcv daIf -PAN -UAO)
> pc : scan_block+0x70/0x190
> lr : scan_block+0x6c/0x190
> sp : ffffff8012e8bd20
> x29: ffffff8012e8bd20 x28: ffffffc0fdbaf018
> x27: ffffffc022000000 x26: 0000000000000080
> x25: ffffff8011aadf70 x24: ffffffc0f8cc8000
> x23: ffffff8010dc8000 x22: ffffff8010dc8830
> x21: ffffffc021e00ff9 x20: ffffffc0f8cc8050
> x19: ffffffc021e00000 x18: 0000000000002409
> x17: 0000000000000200 x16: 0000000000000000
> x15: ffffff8010e14dd8 x14: 0000000000002406
> x13: 000000004c4dd0c6 x12: ffffffc0f77dad58
> x11: 0000000000000001 x10: ffffff8010d9e688
> x9 : ffffff8010d9f000 x8 : ffffff8010d9e688
> x7 : 0000000000000002 x6 : 0000000000000000
> x5 : ffffff8011511c20 x4 : 00000000000026d1
> x3 : ffffff8010e14d88 x2 : 5b36396f4e7d4000
> x1 : 0000000000208040 x0 : 0000000000000000
> Process kmemleak (pid: 523, stack limit = 0x(____ptrval____))
> Call trace:
>  scan_block+0x70/0x190
>  scan_gray_list+0x108/0x1c0
>  kmemleak_scan+0x33c/0x7c0
>  kmemleak_scan_thread+0x98/0xf0
>  kthread+0x11c/0x120
>  ret_from_fork+0x10/0x1c
> Code: f9000fb4 d503201f 97ffffd2 35000580 (f9400260)
> ---[ end trace 176d6ed9d86a0c33 ]---
> note: kmemleak[523] exited with preempt_count 2
>
> The crash happens when a no-map area is allocated in
> early_init_dt_alloc_reserved_memory_arch(). The allocated region is
> registered with kmemleak, but it is then removed from memblock using
> memblock_remove() that is not kmemleak-aware.
>
> Replacing __memblock_alloc_base() with memblock_find_in_range() makes sure
> that the allocated memory is not added to kmemleak and then
> memblock_remove()'ing this memory is safe.
>
> As a bonus, since memblock_find_in_range() ensures the allocation in the
> specified range, the bounds check can be removed.
>
> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Tested-by: Marc Gonzalez <marc.w.gonzalez@xxxxxxx>

With the minor fix mentioned below, you can add my:

Acked-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

> ---
>  drivers/of/of_reserved_mem.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 1977ee0adcb1..6807a1cffe55 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -37,21 +37,16 @@ int __init __weak early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
>  	 */
>  	end = !end ? MEMBLOCK_ALLOC_ANYWHERE : end;
>  	align = !align ? SMP_CACHE_BYTES : align;
> -	base = __memblock_alloc_base(size, align, end);
> +	base = memblock_find_in_range(size, align, start, end);

Please remove a comment about __memblock_alloc_base() above that block
of code. It is no longer needed after this change.

>  	if (!base)
>  		return -ENOMEM;
>  
> -	/*
> -	 * Check if the allocated region fits in to start..end window
> -	 */
> -	if (base < start) {
> -		memblock_free(base, size);
> -		return -ENOMEM;
> -	}
> -
>  	*res_base = base;
>  	if (nomap)
>  		return memblock_remove(base, size);
> +	else
> +		return memblock_reserve(base, size);
> +
>  	return 0;
>  }
>  

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland