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Wed, 17 Jan 2024 14:37:38 -0800 (PST) Date: Wed, 17 Jan 2024 14:37:29 -0800 Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240117223729.1444522-1-lokeshgidra@google.com> Subject: [PATCH] userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb From: Lokesh Gidra To: akpm@linux-foundation.org Cc: lokeshgidra@google.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, selinux@vger.kernel.org, surenb@google.com, kernel-team@android.com, aarcange@redhat.com, peterx@redhat.com, david@redhat.com, axelrasmussen@google.com, bgeffon@google.com, willy@infradead.org, jannh@google.com, kaleshsingh@google.com, ngeoffray@google.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 6519C140003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ac67w6pxemjap7r4gx5iz5o7dq65kkso X-HE-Tag: 1705531059-75022 X-HE-Meta: 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 OrjqJd6G 89CSq7t3MTCETjGPrZz5JXTRszoX5vfdimD2LIlwxK59OGoSqvjibqRZ9RVaQYeUdzThGOp/Ww0N5nM3sfMiRIZFlxS6adwEb963jsXTUu9UtzvNDi1P0DSN/yiJUVm7Sl4WJwvezJCVTLUIAiPfUJES2i0gesNBL0D0PriuvN2h0XTc11R3CyAN792BrjN9kMhi61h2p8rd/EZcnpfgY86VZl19uG721icxRFBSg89C9rT0Fd8P0UlrNAMcaSQxD9tyd1pF/ok5BhsBzt3OdfiuaEV2D2o0t1ENHDlZoO42433nhWiMnrvRyNrnZHtqz4nc705ZxYweg10LgdCio1Nfqbmb1N9jz2wS8jn503WpTbbphynO9nChjxxEb5rJeoUUfeDP0wfw4ruvFu5MY8OssMOrIulaqYqLbkeM5RNvTqEsaIQ+bGDpT8g== 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: List-Subscribe: List-Unsubscribe: In mfill_atomic_hugetlb(), mmap_changing isn't being checked again if we drop mmap_lock and reacquire it. When the lock is not held, mmap_changing could have been incremented. This is also inconsistent with the behavior in mfill_atomic(). Signed-off-by: Lokesh Gidra --- mm/userfaultfd.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 20e3b0d9cf7e..75fcf1f783bc 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -357,6 +357,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb( unsigned long dst_start, unsigned long src_start, unsigned long len, + atomic_t *mmap_changing, uffd_flags_t flags) { struct mm_struct *dst_mm = dst_vma->vm_mm; @@ -472,6 +473,15 @@ static __always_inline ssize_t mfill_atomic_hugetlb( goto out; } mmap_read_lock(dst_mm); + /* + * If memory mappings are changing because of non-cooperative + * operation (e.g. mremap) running in parallel, bail out and + * request the user to retry later + */ + if (mmap_changing && atomic_read(mmap_changing)) { + err = -EAGAIN; + break; + } dst_vma = NULL; goto retry; @@ -506,6 +516,7 @@ extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma, unsigned long dst_start, unsigned long src_start, unsigned long len, + atomic_t *mmap_changing, uffd_flags_t flags); #endif /* CONFIG_HUGETLB_PAGE */ @@ -622,8 +633,8 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm, * If this is a HUGETLB vma, pass off to appropriate routine */ if (is_vm_hugetlb_page(dst_vma)) - return mfill_atomic_hugetlb(dst_vma, dst_start, - src_start, len, flags); + return mfill_atomic_hugetlb(dst_vma, dst_start, src_start, + len, mmap_changing, flags); if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma)) goto out_unlock; -- 2.43.0.429.g432eaa2c6b-goog