* [PATCH] mm: Fix a huge pud insertion race during faulting
@ 2019-10-22 12:30 Thomas Hellström (VMware)
2019-10-24 10:36 ` kbuild test robot
2019-10-24 11:45 ` kbuild test robot
0 siblings, 2 replies; 3+ messages in thread
From: Thomas Hellström (VMware) @ 2019-10-22 12:30 UTC (permalink / raw)
To: linux-kernel, linux-mm; +Cc: Thomas Hellstrom, Matthew Wilcox
From: Thomas Hellstrom <thellstrom@vmware.com>
A huge pud page can theoretically be faulted in racing with pmd_alloc()
in __handle_mm_fault(). That will lead to pmd_alloc() returning an
invalid pmd pointer. Fix this by adding a pud_trans_unstable() function
similar to pmd_trans_unstable() and check whether the pud is really stable
before using the pmd pointer.
Race:
Thread 1: Thread 2: Comment
create_huge_pud() Fallback - not taken.
create_huge_pud() Taken.
pmd_alloc() Returns an invalid pointer.
Cc: Matthew Wilcox <willy@infradead.org>
Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages")
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
---
include/asm-generic/pgtable.h | 25 +++++++++++++++++++++++++
mm/memory.c | 6 ++++++
2 files changed, 31 insertions(+)
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 818691846c90..70c2058230ba 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -912,6 +912,31 @@ static inline int pud_trans_huge(pud_t pud)
}
#endif
+/* See pmd_none_or_trans_huge_or_clear_bad for discussion. */
+static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud)
+{
+ pud_t pudval = READ_ONCE(*pud);
+
+ if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
+ return 1;
+ if (unlikely(pud_bad(pudval))) {
+ pud_clear_bad(pud);
+ return 1;
+ }
+ return 0;
+}
+
+/* See pmd_trans_unstable for discussion. */
+static inline int pud_trans_unstable(pud_t *pud)
+{
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
+ defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
+ return pud_none_or_trans_huge_or_dev_or_clear_bad(pud);
+#else
+ return 0;
+#endif
+}
+
#ifndef pmd_read_atomic
static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
{
diff --git a/mm/memory.c b/mm/memory.c
index b1ca51a079f2..43ff372f4f07 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3914,6 +3914,7 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
vmf.pud = pud_alloc(mm, p4d, address);
if (!vmf.pud)
return VM_FAULT_OOM;
+retry_pud:
if (pud_none(*vmf.pud) && __transparent_hugepage_enabled(vma)) {
ret = create_huge_pud(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
@@ -3940,6 +3941,11 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
vmf.pmd = pmd_alloc(mm, vmf.pud, address);
if (!vmf.pmd)
return VM_FAULT_OOM;
+
+ /* Huge pud page fault raced with pmd_alloc? */
+ if (pud_trans_unstable(vmf.pud))
+ goto retry_pud;
+
if (pmd_none(*vmf.pmd) && __transparent_hugepage_enabled(vma)) {
ret = create_huge_pmd(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
--
2.21.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: Fix a huge pud insertion race during faulting
2019-10-22 12:30 [PATCH] mm: Fix a huge pud insertion race during faulting Thomas Hellström (VMware)
@ 2019-10-24 10:36 ` kbuild test robot
2019-10-24 11:45 ` kbuild test robot
1 sibling, 0 replies; 3+ messages in thread
From: kbuild test robot @ 2019-10-24 10:36 UTC (permalink / raw)
To: Thomas Hellström (VMware)
Cc: kbuild-all, linux-kernel, linux-mm, Thomas Hellstrom, Matthew Wilcox
[-- Attachment #1: Type: text/plain, Size: 3388 bytes --]
Hi "Thomas,
I love your patch! Yet something to improve:
[auto build test ERROR on mmotm/master]
url: https://github.com/0day-ci/linux/commits/Thomas-Hellstr-m-VMware/mm-Fix-a-huge-pud-insertion-race-during-faulting/20191024-175905
base: git://git.cmpxchg.org/linux-mmotm.git master
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
In file included from arch/x86/include/asm/pgtable.h:1466:0,
from include/linux/mm.h:99,
from include/linux/memcontrol.h:20,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from arch/x86/kernel/asm-offsets.c:13:
include/asm-generic/pgtable.h: In function 'pud_none_or_trans_huge_or_dev_or_clear_bad':
>> include/asm-generic/pgtable.h:920:52: error: implicit declaration of function 'pud_devmap'; did you mean 'pud_mkdevmap'? [-Werror=implicit-function-declaration]
if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
^~~~~~~~~~
pud_mkdevmap
In file included from include/linux/memcontrol.h:20:0,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from arch/x86/kernel/asm-offsets.c:13:
include/linux/mm.h: At top level:
>> include/linux/mm.h:572:19: error: static declaration of 'pud_devmap' follows non-static declaration
static inline int pud_devmap(pud_t pud)
^~~~~~~~~~
In file included from arch/x86/include/asm/pgtable.h:1466:0,
from include/linux/mm.h:99,
from include/linux/memcontrol.h:20,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from arch/x86/kernel/asm-offsets.c:13:
include/asm-generic/pgtable.h:920:52: note: previous implicit declaration of 'pud_devmap' was here
if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
^~~~~~~~~~
cc1: some warnings being treated as errors
make[2]: *** [arch/x86/kernel/asm-offsets.s] Error 1
make[2]: Target '__build' not remade because of errors.
make[1]: *** [prepare0] Error 2
make[1]: Target 'prepare' not remade because of errors.
make: *** [sub-make] Error 2
13 real 5 user 3 sys 72.35% cpu make prepare
vim +920 include/asm-generic/pgtable.h
914
915 /* See pmd_none_or_trans_huge_or_clear_bad for discussion. */
916 static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud)
917 {
918 pud_t pudval = READ_ONCE(*pud);
919
> 920 if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
921 return 1;
922 if (unlikely(pud_bad(pudval))) {
923 pud_clear_bad(pud);
924 return 1;
925 }
926 return 0;
927 }
928
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: Fix a huge pud insertion race during faulting
2019-10-22 12:30 [PATCH] mm: Fix a huge pud insertion race during faulting Thomas Hellström (VMware)
2019-10-24 10:36 ` kbuild test robot
@ 2019-10-24 11:45 ` kbuild test robot
1 sibling, 0 replies; 3+ messages in thread
From: kbuild test robot @ 2019-10-24 11:45 UTC (permalink / raw)
To: Thomas Hellström (VMware)
Cc: kbuild-all, linux-kernel, linux-mm, Thomas Hellstrom, Matthew Wilcox
[-- Attachment #1: Type: text/plain, Size: 3061 bytes --]
Hi "Thomas,
I love your patch! Yet something to improve:
[auto build test ERROR on mmotm/master]
url: https://github.com/0day-ci/linux/commits/Thomas-Hellstr-m-VMware/mm-Fix-a-huge-pud-insertion-race-during-faulting/20191024-175905
base: git://git.cmpxchg.org/linux-mmotm.git master
config: um-x86_64_defconfig (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
# save the attached .config to linux build tree
make ARCH=um SUBARCH=x86_64
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
In file included from arch/um/include/asm/pgtable.h:363:0,
from include/linux/mm.h:99,
from include/linux/memcontrol.h:20,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from init/do_mounts.c:7:
include/asm-generic/pgtable.h: In function 'pud_none_or_trans_huge_or_dev_or_clear_bad':
>> include/asm-generic/pgtable.h:920:52: error: implicit declaration of function 'pud_devmap'; did you mean 'put_device'? [-Werror=implicit-function-declaration]
if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
^~~~~~~~~~
put_device
In file included from include/linux/memcontrol.h:20:0,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from init/do_mounts.c:7:
include/linux/mm.h: At top level:
include/linux/mm.h:572:19: error: static declaration of 'pud_devmap' follows non-static declaration
static inline int pud_devmap(pud_t pud)
^~~~~~~~~~
In file included from arch/um/include/asm/pgtable.h:363:0,
from include/linux/mm.h:99,
from include/linux/memcontrol.h:20,
from include/linux/swap.h:9,
from include/linux/suspend.h:5,
from init/do_mounts.c:7:
include/asm-generic/pgtable.h:920:52: note: previous implicit declaration of 'pud_devmap' was here
if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
^~~~~~~~~~
cc1: some warnings being treated as errors
vim +920 include/asm-generic/pgtable.h
914
915 /* See pmd_none_or_trans_huge_or_clear_bad for discussion. */
916 static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud)
917 {
918 pud_t pudval = READ_ONCE(*pud);
919
> 920 if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval))
921 return 1;
922 if (unlikely(pud_bad(pudval))) {
923 pud_clear_bad(pud);
924 return 1;
925 }
926 return 0;
927 }
928
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
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2019-10-24 10:36 ` kbuild test robot
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