* [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine
@ 2017-11-22 12:19 ` Kirill A. Shutemov
0 siblings, 0 replies; 6+ messages in thread
From: Kirill A. Shutemov @ 2017-11-22 12:19 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, linux-api, Michal Hocko,
Kirill A. Shutemov, stable
I've made mistake during converting hugetlb code to 5-level paging:
in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset().
Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc()
if p4d table is not yet allocated.
It only can happen in 5-level paging mode. In 4-level paging mode
p4d_offset() always returns pgd, so we are fine.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
Cc: <stable@vger.kernel.org> # v4.11+
---
mm/hugetlb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2d2ff5e8bf2b..94a4c0b63580 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
pte_t *pte = NULL;
pgd = pgd_offset(mm, addr);
- p4d = p4d_offset(pgd, addr);
+ p4d = p4d_alloc(mm, pgd, addr);
+ if (!p4d)
+ return NULL;
pud = pud_alloc(mm, p4d, addr);
if (pud) {
if (sz == PUD_SIZE) {
--
2.15.0
--
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^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine
2017-11-22 12:19 ` Kirill A. Shutemov
@ 2017-11-22 12:36 ` Vlastimil Babka
-1 siblings, 0 replies; 6+ messages in thread
From: Vlastimil Babka @ 2017-11-22 12:36 UTC (permalink / raw)
To: Kirill A. Shutemov, Andrew Morton
Cc: linux-mm, linux-kernel, linux-api, Michal Hocko, stable
On 11/22/2017 01:19 PM, Kirill A. Shutemov wrote:
> I've made mistake during converting hugetlb code to 5-level paging:
> in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset().
> Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc()
> if p4d table is not yet allocated.
>
> It only can happen in 5-level paging mode. In 4-level paging mode
> p4d_offset() always returns pgd, so we are fine.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
> Cc: <stable@vger.kernel.org> # v4.11+
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2d2ff5e8bf2b..94a4c0b63580 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte_t *pte = NULL;
>
> pgd = pgd_offset(mm, addr);
> - p4d = p4d_offset(pgd, addr);
> + p4d = p4d_alloc(mm, pgd, addr);
> + if (!p4d)
> + return NULL;
> pud = pud_alloc(mm, p4d, addr);
> if (pud) {
> if (sz == PUD_SIZE) {
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine
@ 2017-11-22 12:36 ` Vlastimil Babka
0 siblings, 0 replies; 6+ messages in thread
From: Vlastimil Babka @ 2017-11-22 12:36 UTC (permalink / raw)
To: Kirill A. Shutemov, Andrew Morton
Cc: linux-mm, linux-kernel, linux-api, Michal Hocko, stable
On 11/22/2017 01:19 PM, Kirill A. Shutemov wrote:
> I've made mistake during converting hugetlb code to 5-level paging:
> in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset().
> Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc()
> if p4d table is not yet allocated.
>
> It only can happen in 5-level paging mode. In 4-level paging mode
> p4d_offset() always returns pgd, so we are fine.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
> Cc: <stable@vger.kernel.org> # v4.11+
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2d2ff5e8bf2b..94a4c0b63580 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte_t *pte = NULL;
>
> pgd = pgd_offset(mm, addr);
> - p4d = p4d_offset(pgd, addr);
> + p4d = p4d_alloc(mm, pgd, addr);
> + if (!p4d)
> + return NULL;
> pud = pud_alloc(mm, p4d, addr);
> if (pud) {
> if (sz == PUD_SIZE) {
>
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine
2017-11-22 12:19 ` Kirill A. Shutemov
@ 2017-11-22 12:47 ` Michal Hocko
-1 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2017-11-22 12:47 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Andrew Morton, linux-mm, linux-kernel, linux-api, stable
On Wed 22-11-17 15:19:21, Kirill A. Shutemov wrote:
> I've made mistake during converting hugetlb code to 5-level paging:
> in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset().
> Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc()
> if p4d table is not yet allocated.
Ups, I have completely missed that when reviewing the patch. Sorry about
that.
> It only can happen in 5-level paging mode. In 4-level paging mode
> p4d_offset() always returns pgd, so we are fine.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
> Cc: <stable@vger.kernel.org> # v4.11+
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2d2ff5e8bf2b..94a4c0b63580 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte_t *pte = NULL;
>
> pgd = pgd_offset(mm, addr);
> - p4d = p4d_offset(pgd, addr);
> + p4d = p4d_alloc(mm, pgd, addr);
> + if (!p4d)
> + return NULL;
> pud = pud_alloc(mm, p4d, addr);
> if (pud) {
> if (sz == PUD_SIZE) {
> --
> 2.15.0
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/hugetlb: Fix NULL-pointer dereference on 5-level paging machine
@ 2017-11-22 12:47 ` Michal Hocko
0 siblings, 0 replies; 6+ messages in thread
From: Michal Hocko @ 2017-11-22 12:47 UTC (permalink / raw)
To: Kirill A. Shutemov
Cc: Andrew Morton, linux-mm, linux-kernel, linux-api, stable
On Wed 22-11-17 15:19:21, Kirill A. Shutemov wrote:
> I've made mistake during converting hugetlb code to 5-level paging:
> in huge_pte_alloc() we have to use p4d_alloc(), not p4d_offset().
> Otherwise it leads to crash -- NULL-pointer dereference in pud_alloc()
> if p4d table is not yet allocated.
Ups, I have completely missed that when reviewing the patch. Sorry about
that.
> It only can happen in 5-level paging mode. In 4-level paging mode
> p4d_offset() always returns pgd, so we are fine.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Fixes: c2febafc6773 ("mm: convert generic code to 5-level paging")
> Cc: <stable@vger.kernel.org> # v4.11+
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2d2ff5e8bf2b..94a4c0b63580 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4617,7 +4617,9 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
> pte_t *pte = NULL;
>
> pgd = pgd_offset(mm, addr);
> - p4d = p4d_offset(pgd, addr);
> + p4d = p4d_alloc(mm, pgd, addr);
> + if (!p4d)
> + return NULL;
> pud = pud_alloc(mm, p4d, addr);
> if (pud) {
> if (sz == PUD_SIZE) {
> --
> 2.15.0
--
Michal Hocko
SUSE Labs
--
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^ permalink raw reply [flat|nested] 6+ messages in thread