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

[Ralph Campbell]

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: sta...@vger.kernel.org
Signed-off-by: Ralph Campbell 
Cc: "Jérôme Glisse" 
Cc: Andrew Morton 


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(, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,

migrate->start,

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

[Vlastimil Babka]

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: sta...@vger.kernel.org
> Signed-off-by: Ralph Campbell 
> Cc: "Jérôme Glisse" 
> Cc: Andrew Morton 

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

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

[John Hubbard]

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: sta...@vger.kernel.org
> Signed-off-by: Ralph Campbell 
> Cc: "Jérôme Glisse" 
> Cc: Andrew Morton 
> ---
>  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(, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
>   migrate->start,
> 

Reviewed-by: John Hubbard 

thanks,
-- 
John Hubbard
NVIDIA