diff mbox series

mm, compaction: Make sure we isolate a valid PFN

Message ID 1558711908-15688-1-git-send-email-suzuki.poulose@arm.com
State Accepted
Commit e577c8b64d58fe307ea4d5149d31615df2d90861
Headers show
Series mm, compaction: Make sure we isolate a valid PFN | expand

Commit Message

Suzuki K Poulose May 24, 2019, 3:31 p.m. UTC 
When we have holes in a normal memory zone, we could endup having
cached_migrate_pfns which may not necessarily be valid, under heavy memory
pressure with swapping enabled ( via __reset_isolation_suitable(), triggered
by kswapd).

Later if we fail to find a page via fast_isolate_freepages(), we may
end up using the migrate_pfn we started the search with, as valid
page. This could lead to accessing NULL pointer derefernces like below,
due to an invalid mem_section pointer.

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 [47/1825]
 Mem abort info:
   ESR = 0x96000004
   Exception class = DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
 Data abort info:
   ISV = 0, ISS = 0x00000004
   CM = 0, WnR = 0
 user pgtable: 4k pages, 48-bit VAs, pgdp = 0000000082f94ae9
 [0000000000000008] pgd=0000000000000000
 Internal error: Oops: 96000004 [#1] SMP
 ...
 CPU: 10 PID: 6080 Comm: qemu-system-aar Not tainted 510-rc1+ #6
 Hardware name: AmpereComputing(R) OSPREY EV-883832-X3-0001/OSPREY, BIOS 4819 09/25/2018
 pstate: 60000005 (nZCv daif -PAN -UAO)
 pc : set_pfnblock_flags_mask+0x58/0xe8
 lr : compaction_alloc+0x300/0x950
 [...]
 Process qemu-system-aar (pid: 6080, stack limit = 0x0000000095070da5)
 Call trace:
  set_pfnblock_flags_mask+0x58/0xe8
  compaction_alloc+0x300/0x950
  migrate_pages+0x1a4/0xbb0
  compact_zone+0x750/0xde8
  compact_zone_order+0xd8/0x118
  try_to_compact_pages+0xb4/0x290
  __alloc_pages_direct_compact+0x84/0x1e0
  __alloc_pages_nodemask+0x5e0/0xe18
  alloc_pages_vma+0x1cc/0x210
  do_huge_pmd_anonymous_page+0x108/0x7c8
  __handle_mm_fault+0xdd4/0x1190
  handle_mm_fault+0x114/0x1c0
  __get_user_pages+0x198/0x3c0
  get_user_pages_unlocked+0xb4/0x1d8
  __gfn_to_pfn_memslot+0x12c/0x3b8
  gfn_to_pfn_prot+0x4c/0x60
  kvm_handle_guest_abort+0x4b0/0xcd8
  handle_exit+0x140/0x1b8
  kvm_arch_vcpu_ioctl_run+0x260/0x768
  kvm_vcpu_ioctl+0x490/0x898
  do_vfs_ioctl+0xc4/0x898
  ksys_ioctl+0x8c/0xa0
  __arm64_sys_ioctl+0x28/0x38
  el0_svc_common+0x74/0x118
  el0_svc_handler+0x38/0x78
  el0_svc+0x8/0xc
 Code: f8607840 f100001f 8b011401 9a801020 (f9400400)
 ---[ end trace af6a35219325a9b6 ]---

The issue was reported on an arm64 server with 128GB with holes in the zone
(e.g, [32GB@4GB, 96GB@544GB]), with a swap device enabled, while running 100 KVM
guest instances.

This patch fixes the issue by ensuring that the page belongs to a valid PFN
when we fallback to using the lower limit of the scan range upon failure in
fast_isolate_freepages().

Fixes: 5a811889de10f1eb ("mm, compaction: use free lists to quickly locate a migration target")
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

---
 mm/compaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.7.4

Comments

Mel Gorman May 24, 2019, 3:51 p.m. UTC | #1 
On Fri, May 24, 2019 at 04:31:48PM +0100, Suzuki K Poulose wrote:
> When we have holes in a normal memory zone, we could endup having

> cached_migrate_pfns which may not necessarily be valid, under heavy memory

> pressure with swapping enabled ( via __reset_isolation_suitable(), triggered

> by kswapd).

> 

> Later if we fail to find a page via fast_isolate_freepages(), we may

> end up using the migrate_pfn we started the search with, as valid

> page. This could lead to accessing NULL pointer derefernces like below,

> due to an invalid mem_section pointer.

> 

> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 [47/1825]

>  Mem abort info:

>    ESR = 0x96000004

>    Exception class = DABT (current EL), IL = 32 bits

>    SET = 0, FnV = 0

>    EA = 0, S1PTW = 0

>  Data abort info:

>    ISV = 0, ISS = 0x00000004

>    CM = 0, WnR = 0

>  user pgtable: 4k pages, 48-bit VAs, pgdp = 0000000082f94ae9

>  [0000000000000008] pgd=0000000000000000

>  Internal error: Oops: 96000004 [#1] SMP

>  ...

>  CPU: 10 PID: 6080 Comm: qemu-system-aar Not tainted 510-rc1+ #6

>  Hardware name: AmpereComputing(R) OSPREY EV-883832-X3-0001/OSPREY, BIOS 4819 09/25/2018

>  pstate: 60000005 (nZCv daif -PAN -UAO)

>  pc : set_pfnblock_flags_mask+0x58/0xe8

>  lr : compaction_alloc+0x300/0x950

>  [...]

>  Process qemu-system-aar (pid: 6080, stack limit = 0x0000000095070da5)

>  Call trace:

>   set_pfnblock_flags_mask+0x58/0xe8

>   compaction_alloc+0x300/0x950

>   migrate_pages+0x1a4/0xbb0

>   compact_zone+0x750/0xde8

>   compact_zone_order+0xd8/0x118

>   try_to_compact_pages+0xb4/0x290

>   __alloc_pages_direct_compact+0x84/0x1e0

>   __alloc_pages_nodemask+0x5e0/0xe18

>   alloc_pages_vma+0x1cc/0x210

>   do_huge_pmd_anonymous_page+0x108/0x7c8

>   __handle_mm_fault+0xdd4/0x1190

>   handle_mm_fault+0x114/0x1c0

>   __get_user_pages+0x198/0x3c0

>   get_user_pages_unlocked+0xb4/0x1d8

>   __gfn_to_pfn_memslot+0x12c/0x3b8

>   gfn_to_pfn_prot+0x4c/0x60

>   kvm_handle_guest_abort+0x4b0/0xcd8

>   handle_exit+0x140/0x1b8

>   kvm_arch_vcpu_ioctl_run+0x260/0x768

>   kvm_vcpu_ioctl+0x490/0x898

>   do_vfs_ioctl+0xc4/0x898

>   ksys_ioctl+0x8c/0xa0

>   __arm64_sys_ioctl+0x28/0x38

>   el0_svc_common+0x74/0x118

>   el0_svc_handler+0x38/0x78

>   el0_svc+0x8/0xc

>  Code: f8607840 f100001f 8b011401 9a801020 (f9400400)

>  ---[ end trace af6a35219325a9b6 ]---

> 

> The issue was reported on an arm64 server with 128GB with holes in the zone

> (e.g, [32GB@4GB, 96GB@544GB]), with a swap device enabled, while running 100 KVM

> guest instances.

> 

> This patch fixes the issue by ensuring that the page belongs to a valid PFN

> when we fallback to using the lower limit of the scan range upon failure in

> fast_isolate_freepages().

> 

> Fixes: 5a811889de10f1eb ("mm, compaction: use free lists to quickly locate a migration target")

> Reported-by: Marc Zyngier <marc.zyngier@arm.com>

> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>


Reviewed-by: Mel Gorman <mgorman@techsingularity.net>


-- 
Mel Gorman
SUSE Labs
Anshuman Khandual May 27, 2019, 5:38 a.m. UTC | #2 
On 05/24/2019 09:01 PM, Suzuki K Poulose wrote:
> When we have holes in a normal memory zone, we could endup having

> cached_migrate_pfns which may not necessarily be valid, under heavy memory

> pressure with swapping enabled ( via __reset_isolation_suitable(), triggered

> by kswapd).

> 

> Later if we fail to find a page via fast_isolate_freepages(), we may

> end up using the migrate_pfn we started the search with, as valid

> page. This could lead to accessing NULL pointer derefernces like below,

> due to an invalid mem_section pointer.

> 

> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 [47/1825]

>  Mem abort info:

>    ESR = 0x96000004

>    Exception class = DABT (current EL), IL = 32 bits

>    SET = 0, FnV = 0

>    EA = 0, S1PTW = 0

>  Data abort info:

>    ISV = 0, ISS = 0x00000004

>    CM = 0, WnR = 0

>  user pgtable: 4k pages, 48-bit VAs, pgdp = 0000000082f94ae9

>  [0000000000000008] pgd=0000000000000000

>  Internal error: Oops: 96000004 [#1] SMP

>  ...

>  CPU: 10 PID: 6080 Comm: qemu-system-aar Not tainted 510-rc1+ #6

>  Hardware name: AmpereComputing(R) OSPREY EV-883832-X3-0001/OSPREY, BIOS 4819 09/25/2018

>  pstate: 60000005 (nZCv daif -PAN -UAO)

>  pc : set_pfnblock_flags_mask+0x58/0xe8

>  lr : compaction_alloc+0x300/0x950

>  [...]

>  Process qemu-system-aar (pid: 6080, stack limit = 0x0000000095070da5)

>  Call trace:

>   set_pfnblock_flags_mask+0x58/0xe8

>   compaction_alloc+0x300/0x950

>   migrate_pages+0x1a4/0xbb0

>   compact_zone+0x750/0xde8

>   compact_zone_order+0xd8/0x118

>   try_to_compact_pages+0xb4/0x290

>   __alloc_pages_direct_compact+0x84/0x1e0

>   __alloc_pages_nodemask+0x5e0/0xe18

>   alloc_pages_vma+0x1cc/0x210

>   do_huge_pmd_anonymous_page+0x108/0x7c8

>   __handle_mm_fault+0xdd4/0x1190

>   handle_mm_fault+0x114/0x1c0

>   __get_user_pages+0x198/0x3c0

>   get_user_pages_unlocked+0xb4/0x1d8

>   __gfn_to_pfn_memslot+0x12c/0x3b8

>   gfn_to_pfn_prot+0x4c/0x60

>   kvm_handle_guest_abort+0x4b0/0xcd8

>   handle_exit+0x140/0x1b8

>   kvm_arch_vcpu_ioctl_run+0x260/0x768

>   kvm_vcpu_ioctl+0x490/0x898

>   do_vfs_ioctl+0xc4/0x898

>   ksys_ioctl+0x8c/0xa0

>   __arm64_sys_ioctl+0x28/0x38

>   el0_svc_common+0x74/0x118

>   el0_svc_handler+0x38/0x78

>   el0_svc+0x8/0xc

>  Code: f8607840 f100001f 8b011401 9a801020 (f9400400)

>  ---[ end trace af6a35219325a9b6 ]---

> 

> The issue was reported on an arm64 server with 128GB with holes in the zone

> (e.g, [32GB@4GB, 96GB@544GB]), with a swap device enabled, while running 100 KVM

> guest instances.

> 

> This patch fixes the issue by ensuring that the page belongs to a valid PFN

> when we fallback to using the lower limit of the scan range upon failure in

> fast_isolate_freepages().

> 

> Fixes: 5a811889de10f1eb ("mm, compaction: use free lists to quickly locate a migration target")

> Reported-by: Marc Zyngier <marc.zyngier@arm.com>

> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>


Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
diff mbox series

Patch

diff --git a/mm/compaction.c b/mm/compaction.c
index 9febc8c..9e1b9ac 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1399,7 +1399,7 @@  fast_isolate_freepages(struct compact_control *cc)
 				page = pfn_to_page(highest);
 				cc->free_pfn = highest;
 			} else {
-				if (cc->direct_compaction) {
+				if (cc->direct_compaction && pfn_valid(min_pfn)) {
 					page = pfn_to_page(min_pfn);
 					cc->free_pfn = min_pfn;
 				}