Messages in this thread | | | Date | Tue, 29 Nov 2022 14:26:47 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v3] arm64/mm: fix incorrect file_map_count for invalid pmd |
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On Mon, Nov 28, 2022 at 05:26:14PM +0100, Denys Vlasenko wrote: > On 11/21/22 19:18, Will Deacon wrote: > > On Mon, Nov 21, 2022 at 03:36:08PM +0800, Liu Shixin 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_leaf() will return true even if the pmd is invalid due to > > > pmd_present_invalid() check. So 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. > > > > > > Add !pmd_present_invalid() check in pmd_user_accessible_page() to fix the > > > problem. > > > > > > Fixes: 42b2547137f5 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK") > > > Reported-by: Denys Vlasenko <dvlasenk@redhat.com> > > > Signed-off-by: Liu Shixin <liushixin2@huawei.com> > > > Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com> > > > Acked-by: David Hildenbrand <david@redhat.com> > > > Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > > > --- > > > v1->v2: Update comment and optimize the code by moving p?d_valid() at > > > first place suggested by Mark. > > > v2->v3: Replace pmd_valid() with pmd_present_invalid() suggested by Will. > > > > > > arch/arm64/include/asm/pgtable.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > > > index edf6625ce965..17afb09f386f 100644 > > > --- a/arch/arm64/include/asm/pgtable.h > > > +++ b/arch/arm64/include/asm/pgtable.h > > > @@ -863,7 +863,7 @@ static inline bool pte_user_accessible_page(pte_t pte) > > > 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_present_invalid(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd)); > > > } > > > > Acked-by: Will Deacon <will@kernel.org> > > > > But please see my comment on v2 about pud_user_exec() for the PUD case. > > Can you be more specific? Do you ask for pud_user_exec() to be defined > and used here? Or something else?
So we now have three patches, all from Liu, that are tripping over each other:
1. 5b47348fc0b1 ("arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud")
Merged upstream in -rc6
2. This patch ("arm64/mm: fix incorrect file_map_count for invalid pmd")
This could land for -rc8 (I acked it), but I'd be more comfortable queuing it at -rc1 seeing it as it isn't a recent regression, it explodes in the page-table check code and it will conflict with (1).
3. https://lore.kernel.org/r/20221122123137.429686-1-liushixin2@huawei.com ("arm64/mm: add pud_user_exec() check in pud_user_accessible_page()")
This was just found by inspection, so it can definitely wait for next time (i.e. 6.3).
> Until this patch lands, arm64 PAGE_TABLE_CHECK + THP remains broken...
It's unfortunate, but I don't think it's new breakage and it's failing a synthetic check so it's hard to justify squeezing it in this late.
Will
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