lkml.org 
[lkml]   [2022]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 2/2] arm64/mm: fix incorrect file_map_count for invalid pmd/pud
On Wed, Nov 16, 2022 at 2:51 AM Liu Shixin <liushixin2@huawei.com> wrote:
>
> The page table check trigger BUG_ON() unexpectedly when split hugepage:
>
> ------------[ cut here ]------------
> kernel BUG at mm/page_table_check.c:119!
> Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
> Dumping ftrace buffer:
> (ftrace buffer empty)
> Modules linked in:
> CPU: 7 PID: 210 Comm: transhuge-stres Not tainted 6.1.0-rc3+ #748
> Hardware name: linux,dummy-virt (DT)
> pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : page_table_check_set.isra.0+0x398/0x468
> lr : page_table_check_set.isra.0+0x1c0/0x468
> [...]
> Call trace:
> page_table_check_set.isra.0+0x398/0x468
> __page_table_check_pte_set+0x160/0x1c0
> __split_huge_pmd_locked+0x900/0x1648
> __split_huge_pmd+0x28c/0x3b8
> unmap_page_range+0x428/0x858
> unmap_single_vma+0xf4/0x1c8
> zap_page_range+0x2b0/0x410
> madvise_vma_behavior+0xc44/0xe78
> do_madvise+0x280/0x698
> __arm64_sys_madvise+0x90/0xe8
> invoke_syscall.constprop.0+0xdc/0x1d8
> do_el0_svc+0xf4/0x3f8
> el0_svc+0x58/0x120
> el0t_64_sync_handler+0xb8/0xc0
> el0t_64_sync+0x19c/0x1a0
> [...]
>
> On arm64, pmd_present() will return true even if the pmd is invalid.
> in pmdp_invalidate() the file_map_count will not only decrease once but
> also increase once. Then in set_pte_at(), the file_map_count increase
> again, and so trigger BUG_ON() unexpectedly.

> static inline bool pmd_user_accessible_page(pmd_t pmd)
> {
> - return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> + return pmd_leaf(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)) && pmd_valid(pmd);
> }
>
> static inline bool pud_user_accessible_page(pud_t pud)
> {
> - return pud_leaf(pud) && pud_user(pud);
> + return pud_leaf(pud) && pud_user(pud) && pud_valid(pud);

This looks closer to x86 where the check is directly: pmd_val(pmd) &
_PAGE_PRESENT, without PTE_PROT_NONE that is part of pmd_present()

Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Thanks,
Pasha

\
 
 \ /
  Last update: 2022-11-16 16:20    [W:2.458 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site