* [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
@ 2020-04-14 6:20 Muchun Song
2020-04-14 11:48 ` David Hildenbrand
0 siblings, 1 reply; 7+ messages in thread
From: Muchun Song @ 2020-04-14 6:20 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, Muchun Song, Xiongchun duan
The find_mergeable_vma can return NULL. In this case, it leads
to crash when we access vma->vm_mm(which's offset is 0x40) in
write_protect_page. And this case did happen on our server. The
following calltrace is captured in kernel 4.19 with ksm enabled.
So add a vma check to fix it.
--------------------------------------------------------------------------
BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
PGD 0 P4D 0
Oops: 0000 [#1] SMP NOPTI
CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
RIP: 0010:try_to_merge_one_page+0xc7/0x760
Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
? follow_page_pte+0x36d/0x5e0
ksm_scan_thread+0x115e/0x1960
? remove_wait_queue+0x60/0x60
kthread+0xf5/0x130
? try_to_merge_with_ksm_page+0x90/0x90
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x1f/0x30
--------------------------------------------------------------------------
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
---
mm/ksm.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index a558da9e71770..69b2f85e22d5b 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2112,8 +2112,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
down_read(&mm->mmap_sem);
vma = find_mergeable_vma(mm, rmap_item->address);
- err = try_to_merge_one_page(vma, page,
- ZERO_PAGE(rmap_item->address));
+ if (vma)
+ err = try_to_merge_one_page(vma, page,
+ ZERO_PAGE(rmap_item->address));
+ else
+ err = -EFAULT;
up_read(&mm->mmap_sem);
/*
* In case of failure, the page was not really empty, so we
--
2.11.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
2020-04-14 6:20 [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040 Muchun Song
@ 2020-04-14 11:48 ` David Hildenbrand
2020-04-14 12:09 ` Muchun Song
0 siblings, 1 reply; 7+ messages in thread
From: David Hildenbrand @ 2020-04-14 11:48 UTC (permalink / raw)
To: Muchun Song, akpm; +Cc: linux-mm, linux-kernel, Xiongchun duan
On 14.04.20 08:20, Muchun Song wrote:
> The find_mergeable_vma can return NULL. In this case, it leads
> to crash when we access vma->vm_mm(which's offset is 0x40) in
> write_protect_page. And this case did happen on our server. The
> following calltrace is captured in kernel 4.19 with ksm enabled.
> So add a vma check to fix it.
>
> --------------------------------------------------------------------------
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> PGD 0 P4D 0
> Oops: 0000 [#1] SMP NOPTI
> CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
> Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
> RIP: 0010:try_to_merge_one_page+0xc7/0x760
> Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
> 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
> 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
> RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
> RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
> RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
> RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
> R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
> R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
> FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> PKRU: 55555554
> Call Trace:
> ? follow_page_pte+0x36d/0x5e0
> ksm_scan_thread+0x115e/0x1960
> ? remove_wait_queue+0x60/0x60
> kthread+0xf5/0x130
> ? try_to_merge_with_ksm_page+0x90/0x90
> ? kthread_create_worker_on_cpu+0x70/0x70
> ret_from_fork+0x1f/0x30
> --------------------------------------------------------------------------
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
^ why this signed-off ?
> ---
> mm/ksm.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index a558da9e71770..69b2f85e22d5b 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2112,8 +2112,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
>
> down_read(&mm->mmap_sem);
> vma = find_mergeable_vma(mm, rmap_item->address);
> - err = try_to_merge_one_page(vma, page,
> - ZERO_PAGE(rmap_item->address));
> + if (vma)
> + err = try_to_merge_one_page(vma, page,
> + ZERO_PAGE(rmap_item->address));
> + else
> + err = -EFAULT;
> up_read(&mm->mmap_sem);
> /*
> * In case of failure, the page was not really empty, so we
>
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
2020-04-14 11:48 ` David Hildenbrand
@ 2020-04-14 12:09 ` Muchun Song
0 siblings, 0 replies; 7+ messages in thread
From: Muchun Song @ 2020-04-14 12:09 UTC (permalink / raw)
To: David Hildenbrand
Cc: Andrew Morton, linux-mm, linux-kernel, Xiongchun duan, Markus Elfring
On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 14.04.20 08:20, Muchun Song wrote:
> > The find_mergeable_vma can return NULL. In this case, it leads
> > to crash when we access vma->vm_mm(which's offset is 0x40) in
> > write_protect_page. And this case did happen on our server. The
> > following calltrace is captured in kernel 4.19 with ksm enabled.
> > So add a vma check to fix it.
> >
> > --------------------------------------------------------------------------
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> > PGD 0 P4D 0
> > Oops: 0000 [#1] SMP NOPTI
> > CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
> > Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
> > RIP: 0010:try_to_merge_one_page+0xc7/0x760
> > Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
> > 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
> > 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
> > RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
> > RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
> > RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
> > RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
> > R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
> > R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
> > FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > PKRU: 55555554
> > Call Trace:
> > ? follow_page_pte+0x36d/0x5e0
> > ksm_scan_thread+0x115e/0x1960
> > ? remove_wait_queue+0x60/0x60
> > kthread+0xf5/0x130
> > ? try_to_merge_with_ksm_page+0x90/0x90
> > ? kthread_create_worker_on_cpu+0x70/0x70
> > ret_from_fork+0x1f/0x30
> > --------------------------------------------------------------------------
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
>
> ^ why this signed-off ?
>
Because I have a partner. And I just sent the v2 patch which updates the
commit message and patch subject. Thanks for your review.
> > ---
> > mm/ksm.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/ksm.c b/mm/ksm.c
> > index a558da9e71770..69b2f85e22d5b 100644
> > --- a/mm/ksm.c
> > +++ b/mm/ksm.c
> > @@ -2112,8 +2112,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
> >
> > down_read(&mm->mmap_sem);
> > vma = find_mergeable_vma(mm, rmap_item->address);
> > - err = try_to_merge_one_page(vma, page,
> > - ZERO_PAGE(rmap_item->address));
> > + if (vma)
> > + err = try_to_merge_one_page(vma, page,
> > + ZERO_PAGE(rmap_item->address));
> > + else
> > + err = -EFAULT;
> > up_read(&mm->mmap_sem);
> > /*
> > * In case of failure, the page was not really empty, so we
> >
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
>
> --
> Thanks,
>
> David / dhildenb
>
--
Yours,
Muchun
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
@ 2020-04-14 12:09 ` Muchun Song
0 siblings, 0 replies; 7+ messages in thread
From: Muchun Song @ 2020-04-14 12:09 UTC (permalink / raw)
To: David Hildenbrand
Cc: Andrew Morton, linux-mm, linux-kernel, Xiongchun duan, Markus Elfring
On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 14.04.20 08:20, Muchun Song wrote:
> > The find_mergeable_vma can return NULL. In this case, it leads
> > to crash when we access vma->vm_mm(which's offset is 0x40) in
> > write_protect_page. And this case did happen on our server. The
> > following calltrace is captured in kernel 4.19 with ksm enabled.
> > So add a vma check to fix it.
> >
> > --------------------------------------------------------------------------
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> > PGD 0 P4D 0
> > Oops: 0000 [#1] SMP NOPTI
> > CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
> > Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
> > RIP: 0010:try_to_merge_one_page+0xc7/0x760
> > Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
> > 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
> > 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
> > RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
> > RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
> > RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
> > RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
> > R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
> > R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
> > FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > PKRU: 55555554
> > Call Trace:
> > ? follow_page_pte+0x36d/0x5e0
> > ksm_scan_thread+0x115e/0x1960
> > ? remove_wait_queue+0x60/0x60
> > kthread+0xf5/0x130
> > ? try_to_merge_with_ksm_page+0x90/0x90
> > ? kthread_create_worker_on_cpu+0x70/0x70
> > ret_from_fork+0x1f/0x30
> > --------------------------------------------------------------------------
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
>
> ^ why this signed-off ?
>
Because I have a partner. And I just sent the v2 patch which updates the
commit message and patch subject. Thanks for your review.
> > ---
> > mm/ksm.c | 7 +++++--
> > 1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/ksm.c b/mm/ksm.c
> > index a558da9e71770..69b2f85e22d5b 100644
> > --- a/mm/ksm.c
> > +++ b/mm/ksm.c
> > @@ -2112,8 +2112,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item)
> >
> > down_read(&mm->mmap_sem);
> > vma = find_mergeable_vma(mm, rmap_item->address);
> > - err = try_to_merge_one_page(vma, page,
> > - ZERO_PAGE(rmap_item->address));
> > + if (vma)
> > + err = try_to_merge_one_page(vma, page,
> > + ZERO_PAGE(rmap_item->address));
> > + else
> > + err = -EFAULT;
> > up_read(&mm->mmap_sem);
> > /*
> > * In case of failure, the page was not really empty, so we
> >
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
>
> --
> Thanks,
>
> David / dhildenb
>
--
Yours,
Muchun
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
2020-04-14 12:09 ` Muchun Song
(?)
@ 2020-04-14 12:23 ` David Hildenbrand
2020-04-14 13:01 ` Muchun Song
-1 siblings, 1 reply; 7+ messages in thread
From: David Hildenbrand @ 2020-04-14 12:23 UTC (permalink / raw)
To: Muchun Song
Cc: Andrew Morton, linux-mm, linux-kernel, Xiongchun duan, Markus Elfring
On 14.04.20 14:09, Muchun Song wrote:
> On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
>>
>> On 14.04.20 08:20, Muchun Song wrote:
>>> The find_mergeable_vma can return NULL. In this case, it leads
>>> to crash when we access vma->vm_mm(which's offset is 0x40) in
>>> write_protect_page. And this case did happen on our server. The
>>> following calltrace is captured in kernel 4.19 with ksm enabled.
>>> So add a vma check to fix it.
>>>
>>> --------------------------------------------------------------------------
>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
>>> PGD 0 P4D 0
>>> Oops: 0000 [#1] SMP NOPTI
>>> CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
>>> Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
>>> RIP: 0010:try_to_merge_one_page+0xc7/0x760
>>> Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
>>> 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
>>> 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
>>> RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
>>> RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
>>> RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
>>> RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
>>> R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
>>> R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
>>> FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> PKRU: 55555554
>>> Call Trace:
>>> ? follow_page_pte+0x36d/0x5e0
>>> ksm_scan_thread+0x115e/0x1960
>>> ? remove_wait_queue+0x60/0x60
>>> kthread+0xf5/0x130
>>> ? try_to_merge_with_ksm_page+0x90/0x90
>>> ? kthread_create_worker_on_cpu+0x70/0x70
>>> ret_from_fork+0x1f/0x30
>>> --------------------------------------------------------------------------
>>>
>>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>>> Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
>>
>> ^ why this signed-off ?
>>
>
> Because I have a partner. And I just sent the v2 patch which updates the
> commit message and patch subject. Thanks for your review.
Then we use Co-developed-by AFAIK instead.
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
2020-04-14 12:23 ` David Hildenbrand
@ 2020-04-14 13:01 ` Muchun Song
0 siblings, 0 replies; 7+ messages in thread
From: Muchun Song @ 2020-04-14 13:01 UTC (permalink / raw)
To: David Hildenbrand
Cc: Andrew Morton, linux-mm, linux-kernel, Xiongchun duan, Markus Elfring
On Tue, Apr 14, 2020 at 8:23 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 14.04.20 14:09, Muchun Song wrote:
> > On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
> >>
> >> On 14.04.20 08:20, Muchun Song wrote:
> >>> The find_mergeable_vma can return NULL. In this case, it leads
> >>> to crash when we access vma->vm_mm(which's offset is 0x40) in
> >>> write_protect_page. And this case did happen on our server. The
> >>> following calltrace is captured in kernel 4.19 with ksm enabled.
> >>> So add a vma check to fix it.
> >>>
> >>> --------------------------------------------------------------------------
> >>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> >>> PGD 0 P4D 0
> >>> Oops: 0000 [#1] SMP NOPTI
> >>> CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
> >>> Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
> >>> RIP: 0010:try_to_merge_one_page+0xc7/0x760
> >>> Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
> >>> 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
> >>> 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
> >>> RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
> >>> RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
> >>> RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
> >>> RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
> >>> R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
> >>> R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
> >>> FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
> >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
> >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>> PKRU: 55555554
> >>> Call Trace:
> >>> ? follow_page_pte+0x36d/0x5e0
> >>> ksm_scan_thread+0x115e/0x1960
> >>> ? remove_wait_queue+0x60/0x60
> >>> kthread+0xf5/0x130
> >>> ? try_to_merge_with_ksm_page+0x90/0x90
> >>> ? kthread_create_worker_on_cpu+0x70/0x70
> >>> ret_from_fork+0x1f/0x30
> >>> --------------------------------------------------------------------------
> >>>
> >>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> >>> Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
> >>
> >> ^ why this signed-off ?
> >>
> >
> > Because I have a partner. And I just sent the v2 patch which updates the
> > commit message and patch subject. Thanks for your review.
>
> Then we use Co-developed-by AFAIK instead.
>
Thanks a lot. I will fix it.
--
Yours,
Muchun
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [External] Re: [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040
@ 2020-04-14 13:01 ` Muchun Song
0 siblings, 0 replies; 7+ messages in thread
From: Muchun Song @ 2020-04-14 13:01 UTC (permalink / raw)
To: David Hildenbrand
Cc: Andrew Morton, linux-mm, linux-kernel, Xiongchun duan, Markus Elfring
On Tue, Apr 14, 2020 at 8:23 PM David Hildenbrand <david@redhat.com> wrote:
>
> On 14.04.20 14:09, Muchun Song wrote:
> > On Tue, Apr 14, 2020 at 7:48 PM David Hildenbrand <david@redhat.com> wrote:
> >>
> >> On 14.04.20 08:20, Muchun Song wrote:
> >>> The find_mergeable_vma can return NULL. In this case, it leads
> >>> to crash when we access vma->vm_mm(which's offset is 0x40) in
> >>> write_protect_page. And this case did happen on our server. The
> >>> following calltrace is captured in kernel 4.19 with ksm enabled.
> >>> So add a vma check to fix it.
> >>>
> >>> --------------------------------------------------------------------------
> >>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> >>> PGD 0 P4D 0
> >>> Oops: 0000 [#1] SMP NOPTI
> >>> CPU: 9 PID: 510 Comm: ksmd Kdump: loaded Tainted: G OE 4.19.36.bsk.9-amd64 #4.19.36.bsk.9
> >>> Hardware name: FOXCONN R-5111/GROOT, BIOS IC1B111F 08/17/2019
> >>> RIP: 0010:try_to_merge_one_page+0xc7/0x760
> >>> Code: 24 58 65 48 33 34 25 28 00 00 00 89 e8 0f 85 a3 06 00 00 48 83 c4
> >>> 60 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 46 08 a8 01 75 b8 <49>
> >>> 8b 44 24 40 4c 8d 7c 24 20 b9 07 00 00 00 4c 89 e6 4c 89 ff 48
> >>> RSP: 0018:ffffadbdd9fffdb0 EFLAGS: 00010246
> >>> RAX: ffffda83ffd4be08 RBX: ffffda83ffd4be40 RCX: 0000002c6e800000
> >>> RDX: 0000000000000000 RSI: ffffda83ffd4be40 RDI: 0000000000000000
> >>> RBP: ffffa11939f02ec0 R08: 0000000094e1a447 R09: 00000000abe76577
> >>> R10: 0000000000000962 R11: 0000000000004e6a R12: 0000000000000000
> >>> R13: ffffda83b1e06380 R14: ffffa18f31f072c0 R15: ffffda83ffd4be40
> >>> FS: 0000000000000000(0000) GS:ffffa0da43b80000(0000) knlGS:0000000000000000
> >>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >>> CR2: 0000000000000040 CR3: 0000002c77c0a003 CR4: 00000000007626e0
> >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >>> PKRU: 55555554
> >>> Call Trace:
> >>> ? follow_page_pte+0x36d/0x5e0
> >>> ksm_scan_thread+0x115e/0x1960
> >>> ? remove_wait_queue+0x60/0x60
> >>> kthread+0xf5/0x130
> >>> ? try_to_merge_with_ksm_page+0x90/0x90
> >>> ? kthread_create_worker_on_cpu+0x70/0x70
> >>> ret_from_fork+0x1f/0x30
> >>> --------------------------------------------------------------------------
> >>>
> >>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> >>> Signed-off-by: Xiongchun duan <duanxiongchun@bytedance.com>
> >>
> >> ^ why this signed-off ?
> >>
> >
> > Because I have a partner. And I just sent the v2 patch which updates the
> > commit message and patch subject. Thanks for your review.
>
> Then we use Co-developed-by AFAIK instead.
>
Thanks a lot. I will fix it.
--
Yours,
Muchun
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-04-14 13:02 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-04-14 6:20 [PATCH] mm/ksm: Fix kernel NULL pointer dereference at 0000000000000040 Muchun Song
2020-04-14 11:48 ` David Hildenbrand
2020-04-14 12:09 ` [External] " Muchun Song
2020-04-14 12:09 ` Muchun Song
2020-04-14 12:23 ` David Hildenbrand
2020-04-14 13:01 ` Muchun Song
2020-04-14 13:01 ` Muchun Song
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.