From: "Longpeng(Mike)" <longpeng2@huawei.com>
To: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Cc: Longpeng <longpeng2@huawei.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
Matthew Wilcox <willy@infradead.org>,
Sean Christopherson <sean.j.christopherson@intel.com>,
<stable@vger.kernel.org>
Subject: [PATCH v5] mm/hugetlb: fix a addressing exception caused by huge_pte_offset
Date: Mon, 13 Apr 2020 09:03:42 +0800 [thread overview]
Message-ID: <20200413010342.771-1-longpeng2@huawei.com> (raw)
From: Longpeng <longpeng2@huawei.com>
Our machine encountered a panic(addressing exception) after run
for a long time and the calltrace is:
RIP: 0010:[<ffffffff9dff0587>] [<ffffffff9dff0587>] hugetlb_fault+0x307/0xbe0
RSP: 0018:ffff9567fc27f808 EFLAGS: 00010286
RAX: e800c03ff1258d48 RBX: ffffd3bb003b69c0 RCX: e800c03ff1258d48
RDX: 17ff3fc00eda72b7 RSI: 00003ffffffff000 RDI: e800c03ff1258d48
RBP: ffff9567fc27f8c8 R08: e800c03ff1258d48 R09: 0000000000000080
R10: ffffaba0704c22a8 R11: 0000000000000001 R12: ffff95c87b4b60d8
R13: 00005fff00000000 R14: 0000000000000000 R15: ffff9567face8074
FS: 00007fe2d9ffb700(0000) GS:ffff956900e40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffd3bb003b69c0 CR3: 000000be67374000 CR4: 00000000003627e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
[<ffffffff9df9b71b>] ? unlock_page+0x2b/0x30
[<ffffffff9dff04a2>] ? hugetlb_fault+0x222/0xbe0
[<ffffffff9dff1405>] follow_hugetlb_page+0x175/0x540
[<ffffffff9e15b825>] ? cpumask_next_and+0x35/0x50
[<ffffffff9dfc7230>] __get_user_pages+0x2a0/0x7e0
[<ffffffff9dfc648d>] __get_user_pages_unlocked+0x15d/0x210
[<ffffffffc068cfc5>] __gfn_to_pfn_memslot+0x3c5/0x460 [kvm]
[<ffffffffc06b28be>] try_async_pf+0x6e/0x2a0 [kvm]
[<ffffffffc06b4b41>] tdp_page_fault+0x151/0x2d0 [kvm]
...
[<ffffffffc06a6f90>] kvm_arch_vcpu_ioctl_run+0x330/0x490 [kvm]
[<ffffffffc068d919>] kvm_vcpu_ioctl+0x309/0x6d0 [kvm]
[<ffffffff9deaa8c2>] ? dequeue_signal+0x32/0x180
[<ffffffff9deae34d>] ? do_sigtimedwait+0xcd/0x230
[<ffffffff9e03aed0>] do_vfs_ioctl+0x3f0/0x540
[<ffffffff9e03b0c1>] SyS_ioctl+0xa1/0xc0
[<ffffffff9e53879b>] system_call_fastpath+0x22/0x27
For 1G hugepages, huge_pte_offset() wants to return NULL or pudp, but it
may return a wrong 'pmdp' if there is a race. Please look at the following
code snippet:
...
pud = pud_offset(p4d, addr);
if (sz != PUD_SIZE && pud_none(*pud))
return NULL;
/* hugepage or swap? */
if (pud_huge(*pud) || !pud_present(*pud))
return (pte_t *)pud;
pmd = pmd_offset(pud, addr);
if (sz != PMD_SIZE && pmd_none(*pmd))
return NULL;
/* hugepage or swap? */
if (pmd_huge(*pmd) || !pmd_present(*pmd))
return (pte_t *)pmd;
...
The following sequence would trigger this bug:
1. CPU0: sz = PUD_SIZE and *pud = 0 , continue
1. CPU0: "pud_huge(*pud)" is false
2. CPU1: calling hugetlb_no_page and set *pud to xxxx8e7(PRESENT)
3. CPU0: "!pud_present(*pud)" is false, continue
4. CPU0: pmd = pmd_offset(pud, addr) and maybe return a wrong pmdp
However, we want CPU0 to return NULL or pudp in this case.
We must make sure there is exactly one dereference of pud and pmd.
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Longpeng <longpeng2@huawei.com>
---
v4 -> v5:
fix a bug of on i386
v3 -> v4:
fix a typo s/p4g/p4d. [Jason]
v2 -> v3:
make sure p4d/pud/pmd be dereferenced once. [Jason]
---
mm/hugetlb.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index cd45915..bcabbe0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5365,8 +5365,8 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
{
pgd_t *pgd;
p4d_t *p4d;
- pud_t *pud;
- pmd_t *pmd;
+ pud_t *pud, pud_entry;
+ pmd_t *pmd, pmd_entry;
pgd = pgd_offset(mm, addr);
if (!pgd_present(*pgd))
@@ -5376,17 +5376,19 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
return NULL;
pud = pud_offset(p4d, addr);
- if (sz != PUD_SIZE && pud_none(*pud))
+ pud_entry = READ_ONCE(*pud);
+ if (sz != PUD_SIZE && pud_none(pud_entry))
return NULL;
/* hugepage or swap? */
- if (pud_huge(*pud) || !pud_present(*pud))
+ if (pud_huge(pud_entry) || !pud_present(pud_entry))
return (pte_t *)pud;
pmd = pmd_offset(pud, addr);
- if (sz != PMD_SIZE && pmd_none(*pmd))
+ pmd_entry = READ_ONCE(*pmd);
+ if (sz != PMD_SIZE && pmd_none(pmd_entry))
return NULL;
/* hugepage or swap? */
- if (pmd_huge(*pmd) || !pmd_present(*pmd))
+ if (pmd_huge(pmd_entry) || !pmd_present(pmd_entry))
return (pte_t *)pmd;
return NULL;
--
1.8.3.1
next reply other threads:[~2020-04-13 1:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 1:03 Longpeng(Mike) [this message]
2020-04-13 21:47 ` [PATCH v5] mm/hugetlb: fix a addressing exception caused by huge_pte_offset Mike Kravetz
2020-04-14 19:13 ` Jason Gunthorpe
2020-04-21 19:56 ` Sasha Levin
2020-04-22 1:01 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
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