mm/hugetlb: fix a addressing exception caused by huge_pte_offset
Our machine encountered a panic(addressing exception) after run for a long time and the calltrace is: RIP: 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: follow_hugetlb_page+0x175/0x540 __get_user_pages+0x2a0/0x7e0 __get_user_pages_unlocked+0x15d/0x210 __gfn_to_pfn_memslot+0x3c5/0x460 [kvm] try_async_pf+0x6e/0x2a0 [kvm] tdp_page_fault+0x151/0x2d0 [kvm] ... kvm_arch_vcpu_ioctl_run+0x330/0x490 [kvm] kvm_vcpu_ioctl+0x309/0x6d0 [kvm] do_vfs_ioctl+0x3f0/0x540 SyS_ioctl+0xa1/0xc0 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: - CPU0: sz = PUD_SIZE and *pud = 0 , continue - CPU0: "pud_huge(*pud)" is false - CPU1: calling hugetlb_no_page and set *pud to xxxx8e7(PRESENT) - CPU0: "!pud_present(*pud)" is false, continue - 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. Signed-off-by:Longpeng <longpeng2@huawei.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Reviewed-by:
Mike Kravetz <mike.kravetz@oracle.com> Reviewed-by:
Jason Gunthorpe <jgg@mellanox.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200413010342.771-1-longpeng2@huawei.com Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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