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* [PATCH] mm: fix kernel crash in khugepaged thread
@ 2015-10-23  9:38 ` yalin wang
  0 siblings, 0 replies; 8+ messages in thread
From: yalin wang @ 2015-10-23  9:38 UTC (permalink / raw)
  To: akpm, kirill.shutemov, vbabka, jmarchan, mgorman, ebru.akagunduz,
	willy, linux-mm, linux-kernel
  Cc: yalin wang

This crash is caused by NULL pointer deference:
[  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[  182.639491 ] pgd = ffffffc00077a000
[  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
[  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
[  182.641197 ] Modules linked in:
[  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
[  182.642077 ] Hardware name: linux,dummy-virt (DT)
[  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
[  182.642598 ] PC is at khugepaged+0x378/0x1af8
[  182.642826 ] LR is at khugepaged+0x418/0x1af8
[  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
[  182.643490 ] sp : ffffffc07963bca0
[  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
[  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
[  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
[  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
[  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
[  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
[  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
[  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
[  182.646649 ] x13: 000000000000016a x12: 0000000000000000
[  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
[  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
[  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
[  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
[  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
[  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
[  182.649147 ]
[  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
[  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
[  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
[  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
[  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
[  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
[  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
[  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
[  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
[  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
[  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
[  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
[  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
[  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
[  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
[  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
[  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
[  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
[  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
[  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.661848 ] Call trace:
[  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
[  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
[  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
[  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
[  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
[  182.664160 ] Kernel panic - not syncing: Fatal exception
[  182.664571 ] CPU2: stopping
[  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
[  182.665248 ] Hardware name: linux,dummy-virt (DT)

Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
---
 mm/huge_memory.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b3420a..a5f4d9c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2606,8 +2606,9 @@ out_unmap:
 		collapse_huge_page(mm, address, hpage, vma, node);
 	}
 out:
-	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
-				     none_or_zero, result, unmapped);
+	if (page)
+		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
+				referenced, none_or_zero, result, unmapped);
 	return ret;
 }
 
-- 
1.9.1


^ permalink raw reply related	[flat|nested] 8+ messages in thread
* [PATCH] mm: fix kernel crash in khugepaged thread
@ 2015-10-23  9:38 ` yalin wang
  0 siblings, 0 replies; 8+ messages in thread
From: yalin wang @ 2015-10-23  9:38 UTC (permalink / raw)
  To: akpm, kirill.shutemov, vbabka, jmarchan, mgorman, ebru.akagunduz,
	willy, linux-mm, linux-kernel
  Cc: yalin wang

This crash is caused by NULL pointer deference:
[  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[  182.639491 ] pgd = ffffffc00077a000
[  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
[  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
[  182.641197 ] Modules linked in:
[  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
[  182.642077 ] Hardware name: linux,dummy-virt (DT)
[  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
[  182.642598 ] PC is at khugepaged+0x378/0x1af8
[  182.642826 ] LR is at khugepaged+0x418/0x1af8
[  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
[  182.643490 ] sp : ffffffc07963bca0
[  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
[  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
[  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
[  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
[  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
[  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
[  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
[  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
[  182.646649 ] x13: 000000000000016a x12: 0000000000000000
[  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
[  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
[  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
[  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
[  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
[  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
[  182.649147 ]
[  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
[  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
[  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
[  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
[  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
[  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
[  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
[  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
[  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
[  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
[  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
[  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
[  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
[  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
[  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
[  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
[  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
[  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
[  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
[  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[  182.661848 ] Call trace:
[  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
[  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
[  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
[  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
[  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
[  182.664160 ] Kernel panic - not syncing: Fatal exception
[  182.664571 ] CPU2: stopping
[  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
[  182.665248 ] Hardware name: linux,dummy-virt (DT)

Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
---
 mm/huge_memory.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b3420a..a5f4d9c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2606,8 +2606,9 @@ out_unmap:
 		collapse_huge_page(mm, address, hpage, vma, node);
 	}
 out:
-	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
-				     none_or_zero, result, unmapped);
+	if (page)
+		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
+				referenced, none_or_zero, result, unmapped);
 	return ret;
 }
 
-- 
1.9.1

--
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^ permalink raw reply related	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
  2015-10-23  9:38 ` yalin wang
@ 2015-10-23 10:11   ` Kirill A. Shutemov
  -1 siblings, 0 replies; 8+ messages in thread
From: Kirill A. Shutemov @ 2015-10-23 10:11 UTC (permalink / raw)
  To: yalin wang
  Cc: akpm, kirill.shutemov, vbabka, jmarchan, mgorman, ebru.akagunduz,
	willy, linux-mm, linux-kernel

On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
> This crash is caused by NULL pointer deference:
> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [  182.639491 ] pgd = ffffffc00077a000
> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
> [  182.641197 ] Modules linked in:
> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
> [  182.643490 ] sp : ffffffc07963bca0
> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
> [  182.649147 ]
> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.661848 ] Call trace:
> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
> [  182.664160 ] Kernel panic - not syncing: Fatal exception
> [  182.664571 ] CPU2: stopping
> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
> 
> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
> ---
>  mm/huge_memory.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b3420a..a5f4d9c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2606,8 +2606,9 @@ out_unmap:
>  		collapse_huge_page(mm, address, hpage, vma, node);
>  	}
>  out:
> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
> -				     none_or_zero, result, unmapped);
> +	if (page)
> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
> +				referenced, none_or_zero, result, unmapped);
>  	return ret;
>  }

What about this instead?

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b3420ade697..392ebba27fe2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
 	pmd = mm_find_pmd(mm, address);
-	if (!pmd) {
-		result = SCAN_PMD_NULL;
-		goto out;
-	}
+	if (!pmd)
+		return 0;
 
 	memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
 	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
@@ -2605,7 +2603,6 @@ out_unmap:
 		/* collapse_huge_page will return with the mmap_sem released */
 		collapse_huge_page(mm, address, hpage, vma, node);
 	}
-out:
 	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
 				     none_or_zero, result, unmapped);
 	return ret;
-- 
 Kirill A. Shutemov

^ permalink raw reply related	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
@ 2015-10-23 10:11   ` Kirill A. Shutemov
  0 siblings, 0 replies; 8+ messages in thread
From: Kirill A. Shutemov @ 2015-10-23 10:11 UTC (permalink / raw)
  To: yalin wang
  Cc: akpm, kirill.shutemov, vbabka, jmarchan, mgorman, ebru.akagunduz,
	willy, linux-mm, linux-kernel

On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
> This crash is caused by NULL pointer deference:
> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [  182.639491 ] pgd = ffffffc00077a000
> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
> [  182.641197 ] Modules linked in:
> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
> [  182.643490 ] sp : ffffffc07963bca0
> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
> [  182.649147 ]
> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [  182.661848 ] Call trace:
> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
> [  182.664160 ] Kernel panic - not syncing: Fatal exception
> [  182.664571 ] CPU2: stopping
> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
> 
> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
> ---
>  mm/huge_memory.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b3420a..a5f4d9c 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2606,8 +2606,9 @@ out_unmap:
>  		collapse_huge_page(mm, address, hpage, vma, node);
>  	}
>  out:
> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
> -				     none_or_zero, result, unmapped);
> +	if (page)
> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
> +				referenced, none_or_zero, result, unmapped);
>  	return ret;
>  }

What about this instead?

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4b3420ade697..392ebba27fe2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 
 	pmd = mm_find_pmd(mm, address);
-	if (!pmd) {
-		result = SCAN_PMD_NULL;
-		goto out;
-	}
+	if (!pmd)
+		return 0;
 
 	memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
 	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
@@ -2605,7 +2603,6 @@ out_unmap:
 		/* collapse_huge_page will return with the mmap_sem released */
 		collapse_huge_page(mm, address, hpage, vma, node);
 	}
-out:
 	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
 				     none_or_zero, result, unmapped);
 	return ret;
-- 
 Kirill A. Shutemov

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^ permalink raw reply related	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
  2015-10-23 10:11   ` Kirill A. Shutemov
@ 2015-10-23 16:00     ` yalin wang
  -1 siblings, 0 replies; 8+ messages in thread
From: yalin wang @ 2015-10-23 16:00 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Andrew Morton, Kirill A. Shutemov, Vlastimil Babka, jmarchan,
	mgorman, Ebru Akagunduz, willy, linux-mm, linux-kernel


> On Oct 23, 2015, at 18:11, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> 
> On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
>> This crash is caused by NULL pointer deference:
>> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> [  182.639491 ] pgd = ffffffc00077a000
>> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
>> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
>> [  182.641197 ] Modules linked in:
>> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
>> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
>> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
>> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
>> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
>> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
>> [  182.643490 ] sp : ffffffc07963bca0
>> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
>> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
>> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
>> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
>> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
>> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
>> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
>> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
>> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
>> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
>> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
>> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
>> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
>> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
>> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
>> [  182.649147 ]
>> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
>> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
>> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
>> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
>> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
>> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
>> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
>> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
>> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
>> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
>> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
>> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
>> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
>> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
>> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
>> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
>> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
>> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
>> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
>> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.661848 ] Call trace:
>> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
>> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
>> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
>> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
>> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
>> [  182.664160 ] Kernel panic - not syncing: Fatal exception
>> [  182.664571 ] CPU2: stopping
>> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
>> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
>> 
>> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
>> ---
>> mm/huge_memory.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>> 
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 4b3420a..a5f4d9c 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -2606,8 +2606,9 @@ out_unmap:
>> 		collapse_huge_page(mm, address, hpage, vma, node);
>> 	}
>> out:
>> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
>> -				     none_or_zero, result, unmapped);
>> +	if (page)
>> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
>> +				referenced, none_or_zero, result, unmapped);
>> 	return ret;
>> }
> 
> What about this instead?
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b3420ade697..392ebba27fe2 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
> 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> 
> 	pmd = mm_find_pmd(mm, address);
> -	if (!pmd) {
> -		result = SCAN_PMD_NULL;
> -		goto out;
> -	}
> +	if (!pmd)
> +		return 0;

it is not safe to add return here,
there is lots of place which goto out_unmap below mm_find_pmd() ,
like  page = vm_normal_page(vma, _address, pteval);
if page == NULL here , will also result in NULL pointer deference crash .
Thanks



^ permalink raw reply	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
@ 2015-10-23 16:00     ` yalin wang
  0 siblings, 0 replies; 8+ messages in thread
From: yalin wang @ 2015-10-23 16:00 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Andrew Morton, Kirill A. Shutemov, Vlastimil Babka, jmarchan,
	mgorman, Ebru Akagunduz, willy, linux-mm, linux-kernel


> On Oct 23, 2015, at 18:11, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> 
> On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
>> This crash is caused by NULL pointer deference:
>> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> [  182.639491 ] pgd = ffffffc00077a000
>> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
>> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
>> [  182.641197 ] Modules linked in:
>> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
>> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
>> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
>> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
>> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
>> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
>> [  182.643490 ] sp : ffffffc07963bca0
>> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
>> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
>> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
>> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
>> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
>> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
>> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
>> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
>> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
>> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
>> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
>> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
>> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
>> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
>> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
>> [  182.649147 ]
>> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
>> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
>> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
>> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
>> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
>> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
>> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
>> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
>> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
>> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
>> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
>> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
>> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
>> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
>> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
>> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
>> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
>> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
>> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
>> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> [  182.661848 ] Call trace:
>> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
>> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
>> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
>> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
>> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
>> [  182.664160 ] Kernel panic - not syncing: Fatal exception
>> [  182.664571 ] CPU2: stopping
>> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
>> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
>> 
>> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
>> ---
>> mm/huge_memory.c | 5 +++--
>> 1 file changed, 3 insertions(+), 2 deletions(-)
>> 
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 4b3420a..a5f4d9c 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -2606,8 +2606,9 @@ out_unmap:
>> 		collapse_huge_page(mm, address, hpage, vma, node);
>> 	}
>> out:
>> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
>> -				     none_or_zero, result, unmapped);
>> +	if (page)
>> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
>> +				referenced, none_or_zero, result, unmapped);
>> 	return ret;
>> }
> 
> What about this instead?
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4b3420ade697..392ebba27fe2 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
> 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> 
> 	pmd = mm_find_pmd(mm, address);
> -	if (!pmd) {
> -		result = SCAN_PMD_NULL;
> -		goto out;
> -	}
> +	if (!pmd)
> +		return 0;

it is not safe to add return here,
there is lots of place which goto out_unmap below mm_find_pmd() ,
like  page = vm_normal_page(vma, _address, pteval);
if page == NULL here , will also result in NULL pointer deference crash .
Thanks


--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
  2015-10-23 16:00     ` yalin wang
@ 2015-10-23 19:28       ` Kirill A. Shutemov
  -1 siblings, 0 replies; 8+ messages in thread
From: Kirill A. Shutemov @ 2015-10-23 19:28 UTC (permalink / raw)
  To: yalin wang
  Cc: Andrew Morton, Kirill A. Shutemov, Vlastimil Babka, jmarchan,
	mgorman, Ebru Akagunduz, willy, linux-mm, linux-kernel

On Sat, Oct 24, 2015 at 12:00:14AM +0800, yalin wang wrote:
> 
> > On Oct 23, 2015, at 18:11, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> > 
> > On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
> >> This crash is caused by NULL pointer deference:
> >> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> >> [  182.639491 ] pgd = ffffffc00077a000
> >> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
> >> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
> >> [  182.641197 ] Modules linked in:
> >> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> >> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
> >> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
> >> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
> >> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
> >> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
> >> [  182.643490 ] sp : ffffffc07963bca0
> >> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
> >> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
> >> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
> >> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
> >> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
> >> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
> >> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
> >> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
> >> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
> >> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
> >> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
> >> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
> >> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
> >> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
> >> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
> >> [  182.649147 ]
> >> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
> >> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
> >> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
> >> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
> >> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
> >> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
> >> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
> >> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
> >> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
> >> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
> >> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
> >> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
> >> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
> >> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
> >> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
> >> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
> >> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
> >> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
> >> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
> >> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.661848 ] Call trace:
> >> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
> >> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
> >> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
> >> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
> >> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
> >> [  182.664160 ] Kernel panic - not syncing: Fatal exception
> >> [  182.664571 ] CPU2: stopping
> >> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> >> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
> >> 
> >> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
> >> ---
> >> mm/huge_memory.c | 5 +++--
> >> 1 file changed, 3 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index 4b3420a..a5f4d9c 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -2606,8 +2606,9 @@ out_unmap:
> >> 		collapse_huge_page(mm, address, hpage, vma, node);
> >> 	}
> >> out:
> >> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
> >> -				     none_or_zero, result, unmapped);
> >> +	if (page)
> >> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
> >> +				referenced, none_or_zero, result, unmapped);
> >> 	return ret;
> >> }
> > 
> > What about this instead?
> > 
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 4b3420ade697..392ebba27fe2 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
> > 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> > 
> > 	pmd = mm_find_pmd(mm, address);
> > -	if (!pmd) {
> > -		result = SCAN_PMD_NULL;
> > -		goto out;
> > -	}
> > +	if (!pmd)
> > +		return 0;
> 
> it is not safe to add return here,
> there is lots of place which goto out_unmap below mm_find_pmd() ,
> like  page = vm_normal_page(vma, _address, pteval);
> if page == NULL here , will also result in NULL pointer deference crash .

Fair enough.

But there is no point to set 'result' for these cases.

-- 
 Kirill A. Shutemov

^ permalink raw reply	[flat|nested] 8+ messages in thread
* Re: [PATCH] mm: fix kernel crash in khugepaged thread
@ 2015-10-23 19:28       ` Kirill A. Shutemov
  0 siblings, 0 replies; 8+ messages in thread
From: Kirill A. Shutemov @ 2015-10-23 19:28 UTC (permalink / raw)
  To: yalin wang
  Cc: Andrew Morton, Kirill A. Shutemov, Vlastimil Babka, jmarchan,
	mgorman, Ebru Akagunduz, willy, linux-mm, linux-kernel

On Sat, Oct 24, 2015 at 12:00:14AM +0800, yalin wang wrote:
> 
> > On Oct 23, 2015, at 18:11, Kirill A. Shutemov <kirill@shutemov.name> wrote:
> > 
> > On Fri, Oct 23, 2015 at 05:38:49PM +0800, yalin wang wrote:
> >> This crash is caused by NULL pointer deference:
> >> [  182.639154 ] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> >> [  182.639491 ] pgd = ffffffc00077a000
> >> [  182.639761 ] [00000000] *pgd=00000000b9422003, *pud=00000000b9422003, *pmd=00000000b9423003, *pte=0060000008000707
> >> [  182.640749 ] Internal error: Oops: 94000006 [#1] SMP
> >> [  182.641197 ] Modules linked in:
> >> [  182.641580 ] CPU: 1 PID: 26 Comm: khugepaged Tainted: G        W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> >> [  182.642077 ] Hardware name: linux,dummy-virt (DT)
> >> [  182.642227 ] task: ffffffc07957c080 ti: ffffffc079638000 task.ti: ffffffc079638000
> >> [  182.642598 ] PC is at khugepaged+0x378/0x1af8
> >> [  182.642826 ] LR is at khugepaged+0x418/0x1af8
> >> [  182.643047 ] pc : [<ffffffc0001980ac>] lr : [<ffffffc00019814c>] pstate: 60000145
> >> [  182.643490 ] sp : ffffffc07963bca0
> >> [  182.643650 ] x29: ffffffc07963bca0 x28: ffffffc00075c000
> >> [  182.644024 ] x27: ffffffc00f275040 x26: ffffffc0006c7000
> >> [  182.644334 ] x25: 00e8000048800f51 x24: 0000000006400000
> >> [  182.644687 ] x23: 0000000000000002 x22: 0000000000000000
> >> [  182.644972 ] x21: 0000000000000000 x20: 0000000000000000
> >> [  182.645446 ] x19: 0000000000000000 x18: 0000007ff86d0990
> >> [  182.645931 ] x17: 00000000007ef9c8 x16: ffffffc000098390
> >> [  182.646236 ] x15: ffffffffffffffff x14: 00000000ffffffff
> >> [  182.646649 ] x13: 000000000000016a x12: 0000000000000000
> >> [  182.647046 ] x11: ffffffc07f025020 x10: 0000000000000000
> >> [  182.647395 ] x9 : 0000000000000048 x8 : ffffffc000721e28
> >> [  182.647872 ] x7 : 0000000000000000 x6 : ffffffc07f02d000
> >> [  182.648261 ] x5 : fffffffffffffe00 x4 : ffffffc00f275040
> >> [  182.648611 ] x3 : 0000000000000000 x2 : ffffffc00f2ad000
> >> [  182.648908 ] x1 : 0000000000000000 x0 : ffffffc000727000
> >> [  182.649147 ]
> >> [  182.649252 ] Process khugepaged (pid: 26, stack limit = 0xffffffc079638020)
> >> [  182.649724 ] Stack: (0xffffffc07963bca0 to 0xffffffc07963c000)
> >> [  182.650141 ] bca0: ffffffc07963be30 ffffffc0000b5044 ffffffc07961fb80 ffffffc00072e630
> >> [  182.650587 ] bcc0: ffffffc0005d5090 0000000000000000 ffffffc000197d34 0000000000000000
> >> [  182.651009 ] bce0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.651446 ] bd00: ffffffc07963bd90 ffffffc07f1cbf80 000000004f3be003 ffffffc00f2750a4
> >> [  182.651956 ] bd20: ffffffc00f3bf000 ffffffc000000001 0000000000000001 ffffffc07f085740
> >> [  182.652520 ] bd40: ffffffc00f2ad188 ffffffc000000000 0000000006200000 ffffffc00f275040
> >> [  182.652972 ] bd60: ffffffc0006b1a90 ffffffc079638000 ffffffc07963be20 ffffffc00f0144d0
> >> [  182.653357 ] bd80: ffffffc000000000 0000000006400000 ffffffc00f0144d0 00000a0800000001
> >> [  182.653793 ] bda0: 0000100000000001 ffffffc000000001 ffffffc07f025000 ffffffc00f2750a8
> >> [  182.654226 ] bdc0: 00000001000005f8 ffffffc00075a000 0000000006a00000 ffffffc000727000
> >> [  182.654522 ] bde0: ffffffc0006e8478 ffffffc000000000 0000000100000000 ffffffc078fb9000
> >> [  182.654869 ] be00: ffffffc07963be30 ffffffc000000000 ffffffc07957c080 ffffffc0000cfc4c
> >> [  182.655225 ] be20: ffffffc07963be20 ffffffc07963be20 0000000000000000 ffffffc000085c50
> >> [  182.655588 ] be40: ffffffc0000b4f64 ffffffc07961fb80 0000000000000000 0000000000000000
> >> [  182.656138 ] be60: 0000000000000000 ffffffc0000bee2c ffffffc0000b4f64 0000000000000000
> >> [  182.656609 ] be80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.657145 ] bea0: ffffffc07963bea0 ffffffc07963bea0 0000000000000000 ffffffc000000000
> >> [  182.657475 ] bec0: ffffffc07963bec0 ffffffc07963bec0 0000000000000000 0000000000000000
> >> [  182.657922 ] bee0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.658558 ] bf00: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.658972 ] bf20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.659291 ] bf40: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.659722 ] bf60: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.660122 ] bf80: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.660654 ] bfa0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.661064 ] bfc0: 0000000000000000 0000000000000000 0000000000000000 0000000000000005
> >> [  182.661466 ] bfe0: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >> [  182.661848 ] Call trace:
> >> [  182.662050 ] [<ffffffc0001980ac>] khugepaged+0x378/0x1af8
> >> [  182.662294 ] [<ffffffc0000b5040>] kthread+0xdc/0xf4
> >> [  182.662605 ] [<ffffffc000085c4c>] ret_from_fork+0xc/0x40
> >> [  182.663046 ] Code: 35001700 f0002c60 aa0703e3 f9009fa0 (f94000e0)
> >> [  182.663901 ] ---[ end trace 637503d8e28ae69e  ]---
> >> [  182.664160 ] Kernel panic - not syncing: Fatal exception
> >> [  182.664571 ] CPU2: stopping
> >> [  182.664794 ] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G      D W       4.3.0-rc6-next-20151022ajb-00001-g32f3386-dirty #3
> >> [  182.665248 ] Hardware name: linux,dummy-virt (DT)
> >> 
> >> Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
> >> ---
> >> mm/huge_memory.c | 5 +++--
> >> 1 file changed, 3 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index 4b3420a..a5f4d9c 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -2606,8 +2606,9 @@ out_unmap:
> >> 		collapse_huge_page(mm, address, hpage, vma, node);
> >> 	}
> >> out:
> >> -	trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable, referenced,
> >> -				     none_or_zero, result, unmapped);
> >> +	if (page)
> >> +		trace_mm_khugepaged_scan_pmd(mm, page_to_pfn(page), writable,
> >> +				referenced, none_or_zero, result, unmapped);
> >> 	return ret;
> >> }
> > 
> > What about this instead?
> > 
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 4b3420ade697..392ebba27fe2 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2503,10 +2503,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
> > 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
> > 
> > 	pmd = mm_find_pmd(mm, address);
> > -	if (!pmd) {
> > -		result = SCAN_PMD_NULL;
> > -		goto out;
> > -	}
> > +	if (!pmd)
> > +		return 0;
> 
> it is not safe to add return here,
> there is lots of place which goto out_unmap below mm_find_pmd() ,
> like  page = vm_normal_page(vma, _address, pteval);
> if page == NULL here , will also result in NULL pointer deference crash .

Fair enough.

But there is no point to set 'result' for these cases.

-- 
 Kirill A. Shutemov

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2015-10-23 19:28 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-10-23  9:38 [PATCH] mm: fix kernel crash in khugepaged thread yalin wang
2015-10-23  9:38 ` yalin wang
2015-10-23 10:11 ` Kirill A. Shutemov
2015-10-23 10:11   ` Kirill A. Shutemov
2015-10-23 16:00   ` yalin wang
2015-10-23 16:00     ` yalin wang
2015-10-23 19:28     ` Kirill A. Shutemov
2015-10-23 19:28       ` Kirill A. Shutemov

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