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* [PATCH STABLE ONLY] add missing page refcount overflow checks
@ 2019-11-29  9:03 Vlastimil Babka
  2019-11-29  9:03 ` [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390 Vlastimil Babka
                   ` (3 more replies)
  0 siblings, 4 replies; 9+ messages in thread
From: Vlastimil Babka @ 2019-11-29  9:03 UTC (permalink / raw)
  To: stable
  Cc: Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel, Vlastimil Babka

This collection of patches add the missing overflow checks in arch-specific
gup.c variants for x86 and s390. Those were missed in backport of 8fde12ca79af
("mm: prevent get_user_pages() from overflowing page refcount") as mainline
had a single gup.c implementation at that point. See individual patches for
details.

Vlastimil

-- 
2.24.0


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390
  2019-11-29  9:03 [PATCH STABLE ONLY] add missing page refcount overflow checks Vlastimil Babka
@ 2019-11-29  9:03 ` Vlastimil Babka
  2019-12-03 12:22   ` Ben Hutchings
  2019-11-29  9:03 ` [PATCH STABLE 4.14] mm, gup: add missing refcount overflow checks on s390 Vlastimil Babka
                   ` (2 subsequent siblings)
  3 siblings, 1 reply; 9+ messages in thread
From: Vlastimil Babka @ 2019-11-29  9:03 UTC (permalink / raw)
  To: stable
  Cc: Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel, Vlastimil Babka

The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.9.y stable as commit
2ed768cfd895. The backport however missed that in 4.9, there are several
arch-specific gup.c versions with fast gup implementations, so these do not
prevent refcount overflow.

This is partially fixed for x86 in stable-only commit d73af79742e7 ("x86, mm,
gup: prevent get_page() race with munmap in paravirt guest"). This stable-only
commit adds missing parts to x86 version, as well as s390 version, both taken
from the SUSE SLES/openSUSE 4.12-based kernels.

The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
problem for those architectures, and I don't feel confident enough to patch
them.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 arch/s390/mm/gup.c |  9 ++++++---
 arch/x86/mm/gup.c  | 10 ++++++++--
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 97fc449a7470..33a940389a6d 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -38,7 +38,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+		    || !page_cache_get_speculative(head)))
 			return 0;
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_page(head);
@@ -76,7 +77,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
@@ -150,7 +152,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index d7db45bdfb3b..551fc7fea046 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -202,10 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
 			undo_dev_pagemap(nr, nr_start, pages);
 			return 0;
 		}
+		if (unlikely(!try_get_page(page))) {
+			put_dev_pagemap(pgmap);
+			return 0;
+		}
 		SetPageReferenced(page);
 		pages[*nr] = page;
-		get_page(page);
-		put_dev_pagemap(pgmap);
 		(*nr)++;
 		pfn++;
 	} while (addr += PAGE_SIZE, addr != end);
@@ -230,6 +232,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
 
 	refs = 0;
 	head = pmd_page(pmd);
+	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
+		return 0;
 	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	do {
 		VM_BUG_ON_PAGE(compound_head(page) != head, page);
@@ -289,6 +293,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
 
 	refs = 0;
 	head = pud_page(pud);
+	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
+		return 0;
 	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 	do {
 		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-- 
2.24.0


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH STABLE 4.14] mm, gup: add missing refcount overflow checks on s390
  2019-11-29  9:03 [PATCH STABLE ONLY] add missing page refcount overflow checks Vlastimil Babka
  2019-11-29  9:03 ` [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390 Vlastimil Babka
@ 2019-11-29  9:03 ` Vlastimil Babka
  2019-11-29  9:03 ` [PATCH STABLE 4.19] " Vlastimil Babka
  2019-12-01 16:55 ` [PATCH STABLE ONLY] add missing page refcount overflow checks Sasha Levin
  3 siblings, 0 replies; 9+ messages in thread
From: Vlastimil Babka @ 2019-11-29  9:03 UTC (permalink / raw)
  To: stable
  Cc: Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel, Vlastimil Babka

The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.14.y stable as commit
04198de24771. The backport however missed that in 4.14, there are several
arch-specific gup.c versions with fast gup implementations, so these do not
prevent refcount overflow.

This stable-only commit fixes the s390 version, and is based on the backport in
SUSE SLES/openSUSE 4.12-based kernels.

The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
problem for those architectures, and I don't feel confident enough to patch
them.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 arch/s390/mm/gup.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 05c8abd864f1..9bce54eac0b0 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -39,7 +39,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+		    || !page_cache_get_speculative(head)))
 			return 0;
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_page(head);
@@ -77,7 +78,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
@@ -151,7 +153,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
-- 
2.24.0


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH STABLE 4.19] mm, gup: add missing refcount overflow checks on s390
  2019-11-29  9:03 [PATCH STABLE ONLY] add missing page refcount overflow checks Vlastimil Babka
  2019-11-29  9:03 ` [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390 Vlastimil Babka
  2019-11-29  9:03 ` [PATCH STABLE 4.14] mm, gup: add missing refcount overflow checks on s390 Vlastimil Babka
@ 2019-11-29  9:03 ` " Vlastimil Babka
  2019-12-01 16:55 ` [PATCH STABLE ONLY] add missing page refcount overflow checks Sasha Levin
  3 siblings, 0 replies; 9+ messages in thread
From: Vlastimil Babka @ 2019-11-29  9:03 UTC (permalink / raw)
  To: stable
  Cc: Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel, Vlastimil Babka

The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.19.y stable as commit
d972ebbf42ba. The backport however missed that in 4.19, there are several
arch-specific gup.c versions with fast gup implementations, so these do not
prevent refcount overflow.

This stable-only commit fixes the s390 version, and is based on the backport in
SUSE SLES/openSUSE 4.12-based kernels.

The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
problem for those architectures, and I don't feel confident enough to patch
them.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 arch/s390/mm/gup.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 2809d11c7a28..9b5b866d8adf 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -39,7 +39,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+		    || !page_cache_get_speculative(head)))
 			return 0;
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_page(head);
@@ -77,7 +78,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
@@ -151,7 +153,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs))) {
 		*nr -= refs;
 		return 0;
 	}
-- 
2.24.0


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH STABLE ONLY] add missing page refcount overflow checks
  2019-11-29  9:03 [PATCH STABLE ONLY] add missing page refcount overflow checks Vlastimil Babka
                   ` (2 preceding siblings ...)
  2019-11-29  9:03 ` [PATCH STABLE 4.19] " Vlastimil Babka
@ 2019-12-01 16:55 ` Sasha Levin
  2019-12-03 12:50   ` Vlastimil Babka
  3 siblings, 1 reply; 9+ messages in thread
From: Sasha Levin @ 2019-12-01 16:55 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: stable, Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel

On Fri, Nov 29, 2019 at 10:03:48AM +0100, Vlastimil Babka wrote:
>This collection of patches add the missing overflow checks in arch-specific
>gup.c variants for x86 and s390. Those were missed in backport of 8fde12ca79af
>("mm: prevent get_user_pages() from overflowing page refcount") as mainline
>had a single gup.c implementation at that point. See individual patches for
>details.

Queued up, thanks!

-- 
Thanks,
Sasha

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390
  2019-11-29  9:03 ` [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390 Vlastimil Babka
@ 2019-12-03 12:22   ` Ben Hutchings
  2019-12-03 12:46     ` Vlastimil Babka
  0 siblings, 1 reply; 9+ messages in thread
From: Ben Hutchings @ 2019-12-03 12:22 UTC (permalink / raw)
  To: Vlastimil Babka, stable
  Cc: Matthew Wilcox, Ajay Kaher, linux-mm, linux-kernel

On Fri, 2019-11-29 at 10:03 +0100, Vlastimil Babka wrote:
> The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
> overflowing page refcount") was backported to 4.9.y stable as commit
> 2ed768cfd895. The backport however missed that in 4.9, there are several
> arch-specific gup.c versions with fast gup implementations, so these do not
> prevent refcount overflow.
> 
> This is partially fixed for x86 in stable-only commit d73af79742e7 ("x86, mm,
> gup: prevent get_page() race with munmap in paravirt guest"). This stable-only
> commit adds missing parts to x86 version, as well as s390 version, both taken
> from the SUSE SLES/openSUSE 4.12-based kernels.
> 
> The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
> the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
> problem for those architectures, and I don't feel confident enough to patch
> them.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  arch/s390/mm/gup.c |  9 ++++++---
>  arch/x86/mm/gup.c  | 10 ++++++++--
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
> index 97fc449a7470..33a940389a6d 100644
> --- a/arch/s390/mm/gup.c
> +++ b/arch/s390/mm/gup.c
> @@ -38,7 +38,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
>  		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
>  		page = pte_page(pte);
>  		head = compound_head(page);
> -		if (!page_cache_get_speculative(head))
> +		if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)

No need for unlikely(); WARN_ON() includes that.

> +		    || !page_cache_get_speculative(head)))
>  			return 0;
>  		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
>  			put_page(head);
[...]
> --- a/arch/x86/mm/gup.c
> +++ b/arch/x86/mm/gup.c
> @@ -202,10 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
>  			undo_dev_pagemap(nr, nr_start, pages);
>  			return 0;
>  		}
> +		if (unlikely(!try_get_page(page))) {
> +			put_dev_pagemap(pgmap);
> +			return 0;
> +		}
>  		SetPageReferenced(page);
>  		pages[*nr] = page;
> -		get_page(page);
> -		put_dev_pagemap(pgmap);

This leaks a pgmap reference on success!

>  		(*nr)++;
>  		pfn++;
>  	} while (addr += PAGE_SIZE, addr != end);
> @@ -230,6 +232,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
>  
>  	refs = 0;
>  	head = pmd_page(pmd);
> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))

Why <= 0, given we use < 0 elsewhere?

> +		return 0;
>  	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
>  	do {
>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);
> @@ -289,6 +293,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
>  
>  	refs = 0;
>  	head = pud_page(pud);
> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))

Same question here.

Ben.

> +		return 0;
>  	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
>  	do {
>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390
  2019-12-03 12:22   ` Ben Hutchings
@ 2019-12-03 12:46     ` Vlastimil Babka
  0 siblings, 0 replies; 9+ messages in thread
From: Vlastimil Babka @ 2019-12-03 12:46 UTC (permalink / raw)
  To: Ben Hutchings, stable; +Cc: Matthew Wilcox, Ajay Kaher, linux-mm, linux-kernel

On 12/3/19 1:22 PM, Ben Hutchings wrote:
>> +		    || !page_cache_get_speculative(head)))
>>  			return 0;
>>  		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
>>  			put_page(head);
> [...]
>> --- a/arch/x86/mm/gup.c
>> +++ b/arch/x86/mm/gup.c
>> @@ -202,10 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
>>  			undo_dev_pagemap(nr, nr_start, pages);
>>  			return 0;
>>  		}
>> +		if (unlikely(!try_get_page(page))) {
>> +			put_dev_pagemap(pgmap);
>> +			return 0;
>> +		}
>>  		SetPageReferenced(page);
>>  		pages[*nr] = page;
>> -		get_page(page);
>> -		put_dev_pagemap(pgmap);
> 
> This leaks a pgmap reference on success!

Good catch, deleted one line too many!

>>  		(*nr)++;
>>  		pfn++;
>>  	} while (addr += PAGE_SIZE, addr != end);
>> @@ -230,6 +232,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
>>  
>>  	refs = 0;
>>  	head = pmd_page(pmd);
>> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
> 
> Why <= 0, given we use < 0 elsewhere?

The code uses get_head_page_multiple() which boils down to atomic_add
and not add_unless_zero(), so it assumes a pre-existing pin that must
not go away or it's a bug (one that I've been hunting recently in this
area). The check makes it explicit.

> 
>> +		return 0;
>>  	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
>>  	do {
>>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);
>> @@ -289,6 +293,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
>>  
>>  	refs = 0;
>>  	head = pud_page(pud);
>> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
> 
> Same question here.

Same as above.

> Ben.
> 
>> +		return 0;
>>  	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
>>  	do {
>>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH STABLE ONLY] add missing page refcount overflow checks
  2019-12-01 16:55 ` [PATCH STABLE ONLY] add missing page refcount overflow checks Sasha Levin
@ 2019-12-03 12:50   ` Vlastimil Babka
  2019-12-04 22:52     ` Greg KH
  0 siblings, 1 reply; 9+ messages in thread
From: Vlastimil Babka @ 2019-12-03 12:50 UTC (permalink / raw)
  To: Sasha Levin
  Cc: stable, Ben Hutchings, Matthew Wilcox, Ajay Kaher, linux-mm,
	linux-kernel

On 12/1/19 5:55 PM, Sasha Levin wrote:
> On Fri, Nov 29, 2019 at 10:03:48AM +0100, Vlastimil Babka wrote:
>> This collection of patches add the missing overflow checks in arch-specific
>> gup.c variants for x86 and s390. Those were missed in backport of 8fde12ca79af
>> ("mm: prevent get_user_pages() from overflowing page refcount") as mainline
>> had a single gup.c implementation at that point. See individual patches for
>> details.
> 
> Queued up, thanks!

Please replace the 4.9 version with the following fixed one, thanks to Ben:

----8<----
From fe7f18bd152094f8516d79e847fcb5453a6f8368 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@suse.cz>
Date: Wed, 6 Nov 2019 16:32:57 +0100
Subject: [PATCH] mm, gup: add missing refcount overflow checks on x86 and s390

The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.9.y stable as commit
2ed768cfd895. The backport however missed that in 4.9, there are several
arch-specific gup.c versions with fast gup implementations, so these do not
prevent refcount overflow.

This is partially fixed for x86 in stable-only commit d73af79742e7 ("x86, mm,
gup: prevent get_page() race with munmap in paravirt guest"). This stable-only
commit adds missing parts to x86 version, as well as s390 version, both taken
from the SUSE SLES/openSUSE 4.12-based kernels.

The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
problem for those architectures, and I don't feel confident enough to patch
them.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 arch/s390/mm/gup.c | 9 ++++++---
 arch/x86/mm/gup.c  | 9 ++++++++-
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 97fc449a7470..cf045f56581e 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -38,7 +38,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 		head = compound_head(page);
-		if (!page_cache_get_speculative(head))
+		if (WARN_ON_ONCE(page_ref_count(head) < 0)
+		    || !page_cache_get_speculative(head))
 			return 0;
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
 			put_page(head);
@@ -76,7 +77,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs)) {
 		*nr -= refs;
 		return 0;
 	}
@@ -150,7 +152,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
 		refs++;
 	} while (addr += PAGE_SIZE, addr != end);
 
-	if (!page_cache_add_speculative(head, refs)) {
+	if (WARN_ON_ONCE(page_ref_count(head) < 0)
+	    || !page_cache_add_speculative(head, refs)) {
 		*nr -= refs;
 		return 0;
 	}
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index d7db45bdfb3b..82f727fbbbd2 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -202,9 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
 			undo_dev_pagemap(nr, nr_start, pages);
 			return 0;
 		}
+		if (unlikely(!try_get_page(page))) {
+			put_dev_pagemap(pgmap);
+			return 0;
+		}
 		SetPageReferenced(page);
 		pages[*nr] = page;
-		get_page(page);
 		put_dev_pagemap(pgmap);
 		(*nr)++;
 		pfn++;
@@ -230,6 +233,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
 
 	refs = 0;
 	head = pmd_page(pmd);
+	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
+		return 0;
 	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	do {
 		VM_BUG_ON_PAGE(compound_head(page) != head, page);
@@ -289,6 +294,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
 
 	refs = 0;
 	head = pud_page(pud);
+	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
+		return 0;
 	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 	do {
 		VM_BUG_ON_PAGE(compound_head(page) != head, page);
-- 
2.24.0




^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH STABLE ONLY] add missing page refcount overflow checks
  2019-12-03 12:50   ` Vlastimil Babka
@ 2019-12-04 22:52     ` Greg KH
  0 siblings, 0 replies; 9+ messages in thread
From: Greg KH @ 2019-12-04 22:52 UTC (permalink / raw)
  To: Vlastimil Babka
  Cc: Sasha Levin, stable, Ben Hutchings, Matthew Wilcox, Ajay Kaher,
	linux-mm, linux-kernel

On Tue, Dec 03, 2019 at 01:50:26PM +0100, Vlastimil Babka wrote:
> On 12/1/19 5:55 PM, Sasha Levin wrote:
> > On Fri, Nov 29, 2019 at 10:03:48AM +0100, Vlastimil Babka wrote:
> >> This collection of patches add the missing overflow checks in arch-specific
> >> gup.c variants for x86 and s390. Those were missed in backport of 8fde12ca79af
> >> ("mm: prevent get_user_pages() from overflowing page refcount") as mainline
> >> had a single gup.c implementation at that point. See individual patches for
> >> details.
> > 
> > Queued up, thanks!
> 
> Please replace the 4.9 version with the following fixed one, thanks to Ben:
> 
> ----8<----
> >From fe7f18bd152094f8516d79e847fcb5453a6f8368 Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@suse.cz>
> Date: Wed, 6 Nov 2019 16:32:57 +0100
> Subject: [PATCH] mm, gup: add missing refcount overflow checks on x86 and s390
> 
> The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
> overflowing page refcount") was backported to 4.9.y stable as commit
> 2ed768cfd895. The backport however missed that in 4.9, there are several
> arch-specific gup.c versions with fast gup implementations, so these do not
> prevent refcount overflow.
> 
> This is partially fixed for x86 in stable-only commit d73af79742e7 ("x86, mm,
> gup: prevent get_page() race with munmap in paravirt guest"). This stable-only
> commit adds missing parts to x86 version, as well as s390 version, both taken
> from the SUSE SLES/openSUSE 4.12-based kernels.
> 
> The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
> the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
> problem for those architectures, and I don't feel confident enough to patch
> them.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  arch/s390/mm/gup.c | 9 ++++++---
>  arch/x86/mm/gup.c  | 9 ++++++++-
>  2 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
> index 97fc449a7470..cf045f56581e 100644
> --- a/arch/s390/mm/gup.c
> +++ b/arch/s390/mm/gup.c
> @@ -38,7 +38,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
>  		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
>  		page = pte_page(pte);
>  		head = compound_head(page);
> -		if (!page_cache_get_speculative(head))
> +		if (WARN_ON_ONCE(page_ref_count(head) < 0)
> +		    || !page_cache_get_speculative(head))
>  			return 0;
>  		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
>  			put_page(head);
> @@ -76,7 +77,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
>  		refs++;
>  	} while (addr += PAGE_SIZE, addr != end);
>  
> -	if (!page_cache_add_speculative(head, refs)) {
> +	if (WARN_ON_ONCE(page_ref_count(head) < 0)
> +	    || !page_cache_add_speculative(head, refs)) {
>  		*nr -= refs;
>  		return 0;
>  	}
> @@ -150,7 +152,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr,
>  		refs++;
>  	} while (addr += PAGE_SIZE, addr != end);
>  
> -	if (!page_cache_add_speculative(head, refs)) {
> +	if (WARN_ON_ONCE(page_ref_count(head) < 0)
> +	    || !page_cache_add_speculative(head, refs)) {
>  		*nr -= refs;
>  		return 0;
>  	}
> diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
> index d7db45bdfb3b..82f727fbbbd2 100644
> --- a/arch/x86/mm/gup.c
> +++ b/arch/x86/mm/gup.c
> @@ -202,9 +202,12 @@ static int __gup_device_huge_pmd(pmd_t pmd, unsigned long addr,
>  			undo_dev_pagemap(nr, nr_start, pages);
>  			return 0;
>  		}
> +		if (unlikely(!try_get_page(page))) {
> +			put_dev_pagemap(pgmap);
> +			return 0;
> +		}
>  		SetPageReferenced(page);
>  		pages[*nr] = page;
> -		get_page(page);
>  		put_dev_pagemap(pgmap);
>  		(*nr)++;
>  		pfn++;
> @@ -230,6 +233,8 @@ static noinline int gup_huge_pmd(pmd_t pmd, unsigned long addr,
>  
>  	refs = 0;
>  	head = pmd_page(pmd);
> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
> +		return 0;
>  	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
>  	do {
>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);
> @@ -289,6 +294,8 @@ static noinline int gup_huge_pud(pud_t pud, unsigned long addr,
>  
>  	refs = 0;
>  	head = pud_page(pud);
> +	if (WARN_ON_ONCE(page_ref_count(head) <= 0))
> +		return 0;
>  	page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
>  	do {
>  		VM_BUG_ON_PAGE(compound_head(page) != head, page);
> -- 
> 2.24.0
> 
> 
> 

Now updated, sorry I missed this earlier.

greg k-h

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, back to index

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-29  9:03 [PATCH STABLE ONLY] add missing page refcount overflow checks Vlastimil Babka
2019-11-29  9:03 ` [PATCH STABLE 4.9 1/1] mm, gup: add missing refcount overflow checks on x86 and s390 Vlastimil Babka
2019-12-03 12:22   ` Ben Hutchings
2019-12-03 12:46     ` Vlastimil Babka
2019-11-29  9:03 ` [PATCH STABLE 4.14] mm, gup: add missing refcount overflow checks on s390 Vlastimil Babka
2019-11-29  9:03 ` [PATCH STABLE 4.19] " Vlastimil Babka
2019-12-01 16:55 ` [PATCH STABLE ONLY] add missing page refcount overflow checks Sasha Levin
2019-12-03 12:50   ` Vlastimil Babka
2019-12-04 22:52     ` Greg KH

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