* [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 related [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
* [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 related [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 related [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 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 related [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