Re: [PATCH] arm64: kdump: Skip kmemleak scan reserved memory for kdump

[Catalin Marinas]

On Fri, Aug 27, 2021 at 05:22:46PM +0800, Chen Wandun wrote:
> Trying to boot with kdump + kmemleak, command will result in a crash:
> "echo scan > /sys/kernel/debug/kmemleak"
> 
> crashkernel reserved: 0x0000000007c00000 - 0x0000000027c00000 (512 MB)
> Kernel command line: BOOT_IMAGE=(hd1,gpt2)/vmlinuz-5.14.0-rc5-next-20210809+ root=/dev/mapper/ao-root ro rd.lvm.lv=ao/root rd.lvm.lv=ao/swap crashkernel=512M
> Unable to handle kernel paging request at virtual address ffff000007c00000
> Mem abort info:
>   ESR = 0x96000007
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x07: level 3 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000007
>   CM = 0, WnR = 0
> swapper pgtable: 64k pages, 48-bit VAs, pgdp=00002024f0d80000
> [ffff000007c00000] pgd=1800205ffffd0003, p4d=1800205ffffd0003, pud=1800205ffffd0003, pmd=1800205ffffc0003, pte=0068000007c00f06
> Internal error: Oops: 96000007 [#1] SMP
> pstate: 804000c9 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : scan_block+0x98/0x230
> lr : scan_block+0x94/0x230
> sp : ffff80008d6cfb70
> x29: ffff80008d6cfb70 x28: 0000000000000000 x27: 0000000000000000
> x26: 00000000000000c0 x25: 0000000000000001 x24: 0000000000000000
> x23: ffffa88a6b18b398 x22: ffff000007c00ff9 x21: ffffa88a6ac7fc40
> x20: ffffa88a6af6a830 x19: ffff000007c00000 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: ffffffffffffffff
> x14: ffffffff00000000 x13: ffffffffffffffff x12: 0000000000000020
> x11: 0000000000000000 x10: 0000000001080000 x9 : ffffa88a6951c77c
> x8 : ffffa88a6a893988 x7 : ffff203ff6cfb3c0 x6 : ffffa88a6a52b3c0
> x5 : ffff203ff6cfb3c0 x4 : 0000000000000000 x3 : 0000000000000000
> x2 : 0000000000000001 x1 : ffff20226cb56a40 x0 : 0000000000000000
> Call trace:
>  scan_block+0x98/0x230
>  scan_gray_list+0x120/0x270
>  kmemleak_scan+0x3a0/0x648
>  kmemleak_write+0x3ac/0x4c8
>  full_proxy_write+0x6c/0xa0
>  vfs_write+0xc8/0x2b8
>  ksys_write+0x70/0xf8
>  __arm64_sys_write+0x24/0x30
>  invoke_syscall+0x4c/0x110
>  el0_svc_common+0x9c/0x190
>  do_el0_svc+0x30/0x98
>  el0_svc+0x28/0xd8
>  el0t_64_sync_handler+0x90/0xb8
>  el0t_64_sync+0x180/0x184
> 
> The reserved memory for kdump will be looked up by kmemleak, this area
> will be set invalid when kdump service is bring up. That will result in
> crash when kmemleak scan this area.
> 
> Fixes: 461ef12c4375 ("memblock: make memblock_find_in_range method private")
> Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx>
> ---
>  arch/arm64/mm/init.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index b16be52233c6..dc0c44622bfd 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -30,6 +30,7 @@
>  #include <linux/crash_dump.h>
>  #include <linux/hugetlb.h>
>  #include <linux/acpi_iort.h>
> +#include <linux/kmemleak.h>
>  
>  #include <asm/boot.h>
>  #include <asm/fixmap.h>
> @@ -101,6 +102,7 @@ static void __init reserve_crashkernel(void)
>  	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
>  		crash_base, crash_base + crash_size, crash_size >> 20);
>  
> +	kmemleak_ignore_phys(crash_base);
>  	crashk_res.start = crash_base;
>  	crashk_res.end = crash_base + crash_size - 1;
>  }

I'd add a comment here along the lines of (feel free to change it):

	/*
	 * The crashkernel memory will be removed from the kernel linear
	 * map. Inform kmemleak so that it won't try to access it.
	 */

With that:

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>