linux-kernel - Re: [PATCH] of: fdt: do not reserve memory below MIN_MEMBLOCK

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Message-ID: <CAL_JsqJ3Vi18RizzkKok5Rg8AM3U3Eytaunqk-5RF795ma=wcA@mail.gmail.com>
Date:   Tue, 12 Apr 2022 07:31:16 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Patrick Wang <patrick.wang.shcn@...il.com>,
        Mike Rapoport <rppt@...nel.org>
Cc:     Frank Rowand <frowand.list@...il.com>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of: fdt: do not reserve memory below MIN_MEMBLOCK_ADDR

+Mike Rapoport

On Mon, Apr 11, 2022 at 11:52 PM Patrick Wang
<patrick.wang.shcn@...il.com> wrote:
>
> Dt reserve memory without base checking, which will trigger an oops in
> kmemleak when the base address is below MIN_MEMBLOCK_ADDR:

Why does the caller need to know what this address is? Shouldn't
memblock handle all this internally?

What about when EFI memory maps are used?

>
> # echo scan > /sys/kernel/debug/kmemleak
> [   54.888353] Unable to handle kernel paging request at virtual address ff5fffffffe00000
> [   54.888932] Oops [#1]
> [   54.889102] Modules linked in:
> [   54.889326] CPU: 2 PID: 134 Comm: bash Not tainted 5.18.0-rc1-next-20220407 #33
> [   54.889620] Hardware name: riscv-virtio,qemu (DT)
> [   54.889901] epc : scan_block+0x74/0x15c
> [   54.890215]  ra : scan_block+0x72/0x15c
> [   54.890390] epc : ffffffff801e5806 ra : ffffffff801e5804 sp : ff200000104abc30
> [   54.890607]  gp : ffffffff815cd4e8 tp : ff60000004cfa340 t0 : 0000000000000200
> [   54.890835]  t1 : 00aaaaaac23954cc t2 : 00000000000003ff s0 : ff200000104abc90
> [   54.891024]  s1 : ffffffff81b0ff28 a0 : 0000000000000000 a1 : ff5fffffffe01000
> [   54.891201]  a2 : ffffffff81b0ff28 a3 : 0000000000000002 a4 : 0000000000000001
> [   54.891377]  a5 : 0000000000000000 a6 : ff200000104abd7c a7 : 0000000000000005
> [   54.891552]  s2 : ff5fffffffe00ff9 s3 : ffffffff815cd998 s4 : ffffffff815d0e90
> [   54.891727]  s5 : ffffffff81b0ff28 s6 : 0000000000000020 s7 : ffffffff815d0eb0
> [   54.891903]  s8 : ffffffffffffffff s9 : ff5fffffffe00000 s10: ff5fffffffe01000
> [   54.892078]  s11: 0000000000000022 t3 : 00ffffffaa17db4c t4 : 000000000000000f
> [   54.892271]  t5 : 0000000000000001 t6 : 0000000000000000
> [   54.892408] status: 0000000000000100 badaddr: ff5fffffffe00000 cause: 000000000000000d
> [   54.892643] [<ffffffff801e5a1c>] scan_gray_list+0x12e/0x1a6
> [   54.892824] [<ffffffff801e5d3e>] kmemleak_scan+0x2aa/0x57e
> [   54.892961] [<ffffffff801e633c>] kmemleak_write+0x32a/0x40c
> [   54.893096] [<ffffffff803915ac>] full_proxy_write+0x56/0x82
> [   54.893235] [<ffffffff801ef456>] vfs_write+0xa6/0x2a6
> [   54.893362] [<ffffffff801ef880>] ksys_write+0x6c/0xe2
> [   54.893487] [<ffffffff801ef918>] sys_write+0x22/0x2a
> [   54.893609] [<ffffffff8000397c>] ret_from_syscall+0x0/0x2
> [   54.894183] ---[ end trace 0000000000000000 ]---
>
> Add base checking and ignore the range lower than MIN_MEMBLOCK_ADDR.
>
> Signed-off-by: Patrick Wang <patrick.wang.shcn@...il.com>
> ---
>  drivers/of/fdt.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index ec315b060..296c4ab8e 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -33,6 +33,13 @@
>
>  #include "of_private.h"
>
> +#ifndef MIN_MEMBLOCK_ADDR
> +#define MIN_MEMBLOCK_ADDR      __pa(PAGE_OFFSET)
> +#endif
> +#ifndef MAX_MEMBLOCK_ADDR
> +#define MAX_MEMBLOCK_ADDR      ((phys_addr_t)~0)
> +#endif
> +
>  /*
>   * of_fdt_limit_memory - limit the number of regions in the /memory node
>   * @limit: maximum entries
> @@ -480,6 +487,19 @@ static u32 of_fdt_crc32;
>  static int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
>                                         phys_addr_t size, bool nomap)
>  {
> +       const u64 phys_offset = MIN_MEMBLOCK_ADDR;
> +
> +       if (base < phys_offset) {
> +               pr_warn("Ignoring reserved memory range 0x%llx - 0x%llx\n",
> +                       base, phys_offset);
> +               size = (phys_offset - base) < size ?
> +                       size - (phys_offset - base) : 0;
> +               base = phys_offset;
> +
> +               if (!size)
> +                       return -EFAULT;
> +       }
> +
>         if (nomap) {
>                 /*
>                  * If the memory is already reserved (by another region), we
> @@ -1198,13 +1218,6 @@ int __init early_init_dt_scan_chosen(char *cmdline)
>         return 0;
>  }
>
> -#ifndef MIN_MEMBLOCK_ADDR
> -#define MIN_MEMBLOCK_ADDR      __pa(PAGE_OFFSET)
> -#endif
> -#ifndef MAX_MEMBLOCK_ADDR
> -#define MAX_MEMBLOCK_ADDR      ((phys_addr_t)~0)
> -#endif
> -
>  void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>  {
>         const u64 phys_offset = MIN_MEMBLOCK_ADDR;
> --
> 2.25.1
>