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 <[email protected]>
Signed-off-by: Liu Shixin <[email protected]>
Acked-by: Pasha Tatashin <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Reviewed-by: Kefeng Wang <[email protected]>
---
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));
}
static inline bool pud_user_accessible_page(pud_t pud)
--
2.25.1
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 <[email protected]>
> Signed-off-by: Liu Shixin <[email protected]>
> Acked-by: Pasha Tatashin <[email protected]>
> Acked-by: David Hildenbrand <[email protected]>
> Reviewed-by: Kefeng Wang <[email protected]>
> ---
> 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 <[email protected]>
But please see my comment on v2 about pud_user_exec() for the PUD case.
Will
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 <[email protected]>
>> Signed-off-by: Liu Shixin <[email protected]>
>> Acked-by: Pasha Tatashin <[email protected]>
>> Acked-by: David Hildenbrand <[email protected]>
>> Reviewed-by: Kefeng Wang <[email protected]>
>> ---
>> 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 <[email protected]>
>
> 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?
Until this patch lands, amd64 PAGE_TABLE_CHECK + THP remains broken...
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 <[email protected]>
> > > Signed-off-by: Liu Shixin <[email protected]>
> > > Acked-by: Pasha Tatashin <[email protected]>
> > > Acked-by: David Hildenbrand <[email protected]>
> > > Reviewed-by: Kefeng Wang <[email protected]>
> > > ---
> > > 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 <[email protected]>
> >
> > 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/[email protected]
("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
On Mon, 21 Nov 2022 15:36:08 +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
> [...]
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] arm64/mm: fix incorrect file_map_count for invalid pmd
https://git.kernel.org/arm64/c/74c2f8105451
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev