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b=HlvP9oTBVDsw8FwnPIcA3mJQ389ddOOTZ7DHlr0/W6DzkRduuhdDWQRt203iKFCmQ7xKac /DSUQ9GEFNfweHY9vS6DP2jqudMKZOmUu5SIviAndYFo37/Uhp5sX0CkXorKvRlNFbZYkZ BjIEmhGeVlKTvTdsgUo9iB3OpRfG2C0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1695409588; a=rsa-sha256; cv=none; b=zToi4BrdYqBvx4zYNCXkYH4x+o1H4u+j96F936xEed2hopfhRlMWXFFeAylTWKq/mHc6/d s48kOkPviihPjHVHmQ64K1AEkLwQZpcfgQouQRUtI9V/Xyn+Z9M4l8aCE9jQvifIM0D2TP /4E++avptn2xLLj/P1Qvc+83EDNDuA4= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; spf=none (imf07.hostedemail.com: domain of riel@shelob.surriel.com has no SPF policy when checking 96.67.55.147) smtp.mailfrom=riel@shelob.surriel.com; dmarc=none Received: from imladris.home.surriel.com ([10.0.13.28] helo=imladris.surriel.com) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1qjlTP-0002Wy-1k; Fri, 22 Sep 2023 15:05:55 -0400 From: riel@surriel.com To: linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, linux-mm@kvack.org, akpm@linux-foundation.org, muchun.song@linux.dev, mike.kravetz@oracle.com, leit@meta.com, willy@infradead.org, Rik van Riel Subject: [PATCH 2/3] hugetlbfs: close race between MADV_DONTNEED and page fault Date: Fri, 22 Sep 2023 15:02:30 -0400 Message-ID: <20230922190552.3963067-3-riel@surriel.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230922190552.3963067-1-riel@surriel.com> References: <20230922190552.3963067-1-riel@surriel.com> MIME-Version: 1.0 X-Stat-Signature: ij3s8d4n87myoaderiuzghia93uzudx7 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0D4BC40021 X-Rspam-User: X-HE-Tag: 1695409587-846496 X-HE-Meta: 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 9TSk5Qcc OuxEY2FSmYphHffur5852546k3r1lE+/75+K8i0uckZSPNIk7fW8zoK5URJYv97QiK7t1hO/Ytu9D+KQgVOUNKLCISMZ7b7c10ODRmukkSmzRHdfPXBJsut26pwW8lboHDLGxXQSIPp0+kNOsbZ3LsDz6KU0yrbHeUyNTUs87cS0MX83RufeKkMvdDIvPtNIzCdxkLxnS4Pcyr+7+qjSloJHi9Ldfacp7OjkqnJHMHtRvACQRAFnbuHvNnxBsyLJShdXsj68zgdL0YKXoR6Md0YgkerTZ6gn4plqcl7kRe1WAMGZ3mXdtjvZAl55EqWbBT9bp03AR0tfSldHCRfyYd+/aEA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Rik van Riel Malloc libraries, like jemalloc and tcalloc, take decisions on when to call madvise independently from the code in the main application. This sometimes results in the application page faulting on an address, right after the malloc library has shot down the backing memory with MADV_DONTNEED. Usually this is harmless, because we always have some 4kB pages sitting around to satisfy a page fault. However, with hugetlbfs systems often allocate only the exact number of huge pages that the application wants. Due to TLB batching, hugetlbfs MADV_DONTNEED will free pages outside of any lock taken on the page fault path, which can open up the following race condition: CPU 1 CPU 2 MADV_DONTNEED unmap page shoot down TLB entry page fault fail to allocate a huge page killed with SIGBUS free page Fix that race by pulling the locking from __unmap_hugepage_final_range into helper functions called from zap_page_range_single. This ensures page faults stay locked out of the MADV_DONTNEED VMA until the huge pages have actually been freed. Signed-off-by: Rik van Riel --- include/linux/hugetlb.h | 35 +++++++++++++++++++++++++++++++++-- mm/hugetlb.c | 20 +++++++++++--------- mm/memory.c | 7 +++---- 3 files changed, 47 insertions(+), 15 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 694928fa06a3..d9ec500cfef9 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -139,7 +139,7 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long, struct page *, zap_flags_t); -void __unmap_hugepage_range_final(struct mmu_gather *tlb, +void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, struct page *ref_page, zap_flags_t zap_flags); @@ -246,6 +246,25 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma, unsigned long *start, unsigned long *end); +extern void __hugetlb_zap_begin(struct vm_area_struct *vma, + unsigned long *begin, unsigned long *end); +extern void __hugetlb_zap_end(struct vm_area_struct *vma, + struct zap_details *details); + +static inline void hugetlb_zap_begin(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ + if (is_vm_hugetlb_page(vma)) + __hugetlb_zap_begin(vma, start, end); +} + +static inline void hugetlb_zap_end(struct vm_area_struct *vma, + struct zap_details *details) +{ + if (is_vm_hugetlb_page(vma)) + __hugetlb_zap_end(vma, details); +} + void hugetlb_vma_lock_read(struct vm_area_struct *vma); void hugetlb_vma_unlock_read(struct vm_area_struct *vma); void hugetlb_vma_lock_write(struct vm_area_struct *vma); @@ -297,6 +316,18 @@ static inline void adjust_range_if_pmd_sharing_possible( { } +static inline void hugetlb_zap_begin( + struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ +} + +static inline void hugetlb_zap_end( + struct vm_area_struct *vma, + struct zap_details *details) +{ +} + static inline struct page *hugetlb_follow_page_mask( struct vm_area_struct *vma, unsigned long address, unsigned int flags, unsigned int *page_mask) @@ -442,7 +473,7 @@ static inline long hugetlb_change_protection( return 0; } -static inline void __unmap_hugepage_range_final(struct mmu_gather *tlb, +static inline void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, unsigned long start, unsigned long end, struct page *ref_page, zap_flags_t zap_flags) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ee7497f37098..397a26f70deb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5306,9 +5306,9 @@ int move_hugetlb_page_tables(struct vm_area_struct *vma, return len + old_addr - old_end; } -static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, - unsigned long start, unsigned long end, - struct page *ref_page, zap_flags_t zap_flags) +void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, + unsigned long start, unsigned long end, + struct page *ref_page, zap_flags_t zap_flags) { struct mm_struct *mm = vma->vm_mm; unsigned long address; @@ -5435,16 +5435,18 @@ static void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct tlb_flush_mmu_tlbonly(tlb); } -void __unmap_hugepage_range_final(struct mmu_gather *tlb, - struct vm_area_struct *vma, unsigned long start, - unsigned long end, struct page *ref_page, - zap_flags_t zap_flags) +void __hugetlb_zap_begin(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) { + adjust_range_if_pmd_sharing_possible(vma, start, end); hugetlb_vma_lock_write(vma); i_mmap_lock_write(vma->vm_file->f_mapping); +} - /* mmu notification performed in caller */ - __unmap_hugepage_range(tlb, vma, start, end, ref_page, zap_flags); +void __hugetlb_zap_end(struct vm_area_struct *vma, + struct zap_details *details) +{ + zap_flags_t zap_flags = details ? details->zap_flags : 0; if (zap_flags & ZAP_FLAG_UNMAP) { /* final unmap */ /* diff --git a/mm/memory.c b/mm/memory.c index 6c264d2f969c..a07ae3b60530 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1683,7 +1683,7 @@ static void unmap_single_vma(struct mmu_gather *tlb, if (vma->vm_file) { zap_flags_t zap_flags = details ? details->zap_flags : 0; - __unmap_hugepage_range_final(tlb, vma, start, end, + __unmap_hugepage_range(tlb, vma, start, end, NULL, zap_flags); } } else @@ -1753,9 +1753,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address, lru_add_drain(); mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, address, end); - if (is_vm_hugetlb_page(vma)) - adjust_range_if_pmd_sharing_possible(vma, &range.start, - &range.end); + hugetlb_zap_begin(vma, &range.start, &range.end); tlb_gather_mmu(&tlb, vma->vm_mm); update_hiwater_rss(vma->vm_mm); mmu_notifier_invalidate_range_start(&range); @@ -1766,6 +1764,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address, unmap_single_vma(&tlb, vma, address, end, details, false); mmu_notifier_invalidate_range_end(&range); tlb_finish_mmu(&tlb); + hugetlb_zap_end(vma, details); } /**