2019-07-20 00:39:43

by Ralph Campbell

Subject: [PATCH] mm/migrate: initialize pud_entry in migrate_vma()

When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
migrate_vma_collect() which initializes a struct mm_walk but
didn't initialize mm_walk.pud_entry. (Found by code inspection)
Use a C structure initialization to make sure it is set to NULL.

Fixes: 8763cb45ab967 ("mm/migrate: new memory migration helper for use with
device memory")
Cc: [email protected]
Signed-off-by: Ralph Campbell <[email protected]>
Cc: "Jérôme Glisse" <[email protected]>
Cc: Andrew Morton <[email protected]>
---
mm/migrate.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 515718392b24..a42858d8e00b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2340,16 +2340,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
static void migrate_vma_collect(struct migrate_vma *migrate)
{
struct mmu_notifier_range range;
- struct mm_walk mm_walk;
-
- mm_walk.pmd_entry = migrate_vma_collect_pmd;
- mm_walk.pte_entry = NULL;
- mm_walk.pte_hole = migrate_vma_collect_hole;
- mm_walk.hugetlb_entry = NULL;
- mm_walk.test_walk = NULL;
- mm_walk.vma = migrate->vma;
- mm_walk.mm = migrate->vma->vm_mm;
- mm_walk.private = migrate;
+ struct mm_walk mm_walk = {
+ .pmd_entry = migrate_vma_collect_pmd,
+ .pte_hole = migrate_vma_collect_hole,
+ .vma = migrate->vma,
+ .mm = migrate->vma->vm_mm,
+ .private = migrate,
+ };

mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
migrate->start,
--
2.20.1

2019-07-20 12:53:49

by John Hubbard

Subject: Re: [PATCH] mm/migrate: initialize pud_entry in migrate_vma()

On 7/19/19 4:32 PM, Ralph Campbell wrote:
> When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
> migrate_vma_collect() which initializes a struct mm_walk but
> didn't initialize mm_walk.pud_entry. (Found by code inspection)
> Use a C structure initialization to make sure it is set to NULL.
>
> Fixes: 8763cb45ab967 ("mm/migrate: new memory migration helper for use with
> device memory")
> Cc: [email protected]
> Signed-off-by: Ralph Campbell <[email protected]>
> Cc: "Jérôme Glisse" <[email protected]>
> Cc: Andrew Morton <[email protected]>
> ---
> mm/migrate.c | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 515718392b24..a42858d8e00b 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2340,16 +2340,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> static void migrate_vma_collect(struct migrate_vma *migrate)
> {
> struct mmu_notifier_range range;
> - struct mm_walk mm_walk;
> -
> - mm_walk.pmd_entry = migrate_vma_collect_pmd;
> - mm_walk.pte_entry = NULL;
> - mm_walk.pte_hole = migrate_vma_collect_hole;
> - mm_walk.hugetlb_entry = NULL;
> - mm_walk.test_walk = NULL;
> - mm_walk.vma = migrate->vma;
> - mm_walk.mm = migrate->vma->vm_mm;
> - mm_walk.private = migrate;
> + struct mm_walk mm_walk = {
> + .pmd_entry = migrate_vma_collect_pmd,
> + .pte_hole = migrate_vma_collect_hole,
> + .vma = migrate->vma,
> + .mm = migrate->vma->vm_mm,
> + .private = migrate,
> + };

Neatly done.

>
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
> migrate->start,
>

Reviewed-by: John Hubbard <[email protected]>

thanks,
--
John Hubbard
NVIDIA

2019-08-26 15:41:07

by Vlastimil Babka

Subject: Re: [PATCH] mm/migrate: initialize pud_entry in migrate_vma()

On 7/20/19 1:32 AM, Ralph Campbell wrote:
> When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
> migrate_vma_collect() which initializes a struct mm_walk but
> didn't initialize mm_walk.pud_entry. (Found by code inspection)
> Use a C structure initialization to make sure it is set to NULL.
>
> Fixes: 8763cb45ab967 ("mm/migrate: new memory migration helper for use with
> device memory")
> Cc: [email protected]
> Signed-off-by: Ralph Campbell <[email protected]>
> Cc: "Jérôme Glisse" <[email protected]>
> Cc: Andrew Morton <[email protected]>

So this bug can manifest by some garbage address on stack being called, right? I
wonder, how comes it didn't actually happen yet?

> ---
> mm/migrate.c | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 515718392b24..a42858d8e00b 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2340,16 +2340,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> static void migrate_vma_collect(struct migrate_vma *migrate)
> {
> struct mmu_notifier_range range;
> - struct mm_walk mm_walk;
> -
> - mm_walk.pmd_entry = migrate_vma_collect_pmd;
> - mm_walk.pte_entry = NULL;
> - mm_walk.pte_hole = migrate_vma_collect_hole;
> - mm_walk.hugetlb_entry = NULL;
> - mm_walk.test_walk = NULL;
> - mm_walk.vma = migrate->vma;
> - mm_walk.mm = migrate->vma->vm_mm;
> - mm_walk.private = migrate;
> + struct mm_walk mm_walk = {
> + .pmd_entry = migrate_vma_collect_pmd,
> + .pte_hole = migrate_vma_collect_hole,
> + .vma = migrate->vma,
> + .mm = migrate->vma->vm_mm,
> + .private = migrate,
> + };
>
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
> migrate->start,
>

2019-08-26 19:38:53

by Ralph Campbell

Subject: Re: [PATCH] mm/migrate: initialize pud_entry in migrate_vma()

On 8/26/19 8:11 AM, Vlastimil Babka wrote:
> On 7/20/19 1:32 AM, Ralph Campbell wrote:
>> When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
>> migrate_vma_collect() which initializes a struct mm_walk but
>> didn't initialize mm_walk.pud_entry. (Found by code inspection)
>> Use a C structure initialization to make sure it is set to NULL.
>>
>> Fixes: 8763cb45ab967 ("mm/migrate: new memory migration helper for use with
>> device memory")
>> Cc: [email protected]
>> Signed-off-by: Ralph Campbell <[email protected]>
>> Cc: "Jérôme Glisse" <[email protected]>
>> Cc: Andrew Morton <[email protected]>
>
> So this bug can manifest by some garbage address on stack being called, right? I
> wonder, how comes it didn't actually happen yet?

Right.
Probably because HMM isn't widely being used in production yet.

>
>> ---
>> mm/migrate.c | 17 +++++++----------
>> 1 file changed, 7 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 515718392b24..a42858d8e00b 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -2340,16 +2340,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>> static void migrate_vma_collect(struct migrate_vma *migrate)
>> {
>> struct mmu_notifier_range range;
>> - struct mm_walk mm_walk;
>> -
>> - mm_walk.pmd_entry = migrate_vma_collect_pmd;
>> - mm_walk.pte_entry = NULL;
>> - mm_walk.pte_hole = migrate_vma_collect_hole;
>> - mm_walk.hugetlb_entry = NULL;
>> - mm_walk.test_walk = NULL;
>> - mm_walk.vma = migrate->vma;
>> - mm_walk.mm = migrate->vma->vm_mm;
>> - mm_walk.private = migrate;
>> + struct mm_walk mm_walk = {
>> + .pmd_entry = migrate_vma_collect_pmd,
>> + .pte_hole = migrate_vma_collect_hole,
>> + .vma = migrate->vma,
>> + .mm = migrate->vma->vm_mm,
>> + .private = migrate,
>> + };
>>
>> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
>> migrate->start,
>>
>