linux-kernel - Re: [PATCH] mm: kmemleak: take a full lowmem check in kmemleak_*

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Date:   Thu, 14 Apr 2022 18:26:56 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Patrick Wang <patrick.wang.shcn@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: kmemleak: take a full lowmem check in
 kmemleak_*_phys()

On Wed, Apr 13, 2022 at 08:29:25PM +0800, Patrick Wang wrote:
> The kmemleak_*_phys() apis do not check the address for lowmem's min
> boundary, while the caller may pass an address below lowmem, which
> will trigger an oops:
> 
> # 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

Acked-by: Catalin Marinas <catalin.marinas@....com>