From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC119C5479D for ; Mon, 9 Jan 2023 20:56:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237713AbjAIU4S (ORCPT ); Mon, 9 Jan 2023 15:56:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237640AbjAIUzd (ORCPT ); Mon, 9 Jan 2023 15:55:33 -0500 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54C23848F7 for ; Mon, 9 Jan 2023 12:54:30 -0800 (PST) Received: by mail-yb1-xb4a.google.com with SMTP id w15-20020a05690204ef00b007b966ba4410so7175454ybs.5 for ; Mon, 09 Jan 2023 12:54:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=ves4Zx76RBv25M18zzcj7gVloTdTuNMdyKmYC5DDvz0=; b=MKIFYUVg3C+KcUmk/DiJLvwQZvDLVNMlr8DQ0MCXFdkv6hN2eBfUWDzxIZ7BfVHp8I 9ZQKQbnc3cjtIsfRVDcXo71Ba38rTMbcUdq5jPPQ/O/qUYTP0dyF6taFqjbQZ9FRkBHu 4AhRyAaM/Xs1rNZHH4s644beTjAgsiLfyufSEIgttXRExgdKqL3ufxpDIm4mlvORyhtg 8KPqhXKz4czDblD/OO3yCfwh5TQTP8fNUj9/04RnIZEyuuEXUuTlBqAldxaXV0tj/mD/ bYzPmov2AWSWqL0UrgwZuK2hqucg36ElYTON5SUI9h/73LoxJPTGa7ERIj/8Aw4bHycM nzHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ves4Zx76RBv25M18zzcj7gVloTdTuNMdyKmYC5DDvz0=; b=cKW5U6PtxhwR348hIPI16LT/msHQ3L7R4hiIO1BA0MCRzrTnS6IvePIpht9FiXpOax TFRWUWo6MzLbl1eQ2BoqA/GvbU2bQxkDmLUvg8U91I49DHmsuCo3UapsyREKyNPC7uHO NoYnDL8MxTHrOiNmdgFluTitEbl33jWVsY9Ci4i47ci6rAdhyaYKEJB3iIMF+uFHYri4 vqWvSKUEKzAWlAoKlVQfF7ffMFfn0dfuGAu3TRWFaBp9OCxaLGgcpRzTNDf75BffHk97 hnAC70rOy0OTPXCah4QeAun9aW0WSqBZwMZDKtJ3HeGmC20M4E1G0JZ7Ft3/zHah893G oGsw== X-Gm-Message-State: AFqh2koVPSfy7cFw3J/Al13Q5l+X4YxnOUwStW73V6MoKOHFGuFcWEcc teWWgDxX1vK1oLfe8ZoRcOJRn2IyLiU= X-Google-Smtp-Source: AMrXdXvMc8uw91kFZQ5TZdRrbkHWe3EKuKErf5QuBh5uD1fMXXAng4XpjPLPHBE1E+VnZgCLzgnV8hcsb8Y= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:9393:6f7a:d410:55ca]) (user=surenb job=sendgmr) by 2002:a81:a013:0:b0:4a9:884a:20c4 with SMTP id x19-20020a81a013000000b004a9884a20c4mr4780346ywg.139.1673297669408; Mon, 09 Jan 2023 12:54:29 -0800 (PST) Date: Mon, 9 Jan 2023 12:53:14 -0800 In-Reply-To: <20230109205336.3665937-1-surenb@google.com> Mime-Version: 1.0 References: <20230109205336.3665937-1-surenb@google.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog Message-ID: <20230109205336.3665937-20-surenb@google.com> Subject: [PATCH 19/41] mm/mmap: write-lock VMAs before merging, splitting or expanding them From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com, surenb@google.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Decisions about whether VMAs can be merged, split or expanded must be made while VMAs are protected from the changes which can affect that decision. For example, merge_vma uses vma->anon_vma in its decision whether the VMA can be merged. Meanwhile, page fault handler changes vma->anon_vma during COW operation. Write-lock all VMAs which might be affected by a merge or split operation before making decision how such operations should be performed. Not sure if expansion really needs this, just being paranoid. Otherwise mmap_region and vm_brk_flags might not locking. Signed-off-by: Suren Baghdasaryan --- mm/mmap.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 53d885e70a54..f6ca4a87f9e2 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -254,8 +254,11 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) */ mas_set(&mas, oldbrk); next = mas_find(&mas, newbrk - 1 + PAGE_SIZE + stack_guard_gap); - if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) - goto out; + if (next) { + vma_write_lock(next); + if (newbrk + PAGE_SIZE > vm_start_gap(next)) + goto out; + } brkvma = mas_prev(&mas, mm->start_brk); /* Ok, looks good - let it rip. */ @@ -1017,10 +1020,17 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, if (vm_flags & VM_SPECIAL) return NULL; + if (prev) + vma_write_lock(prev); next = find_vma(mm, prev ? prev->vm_end : 0); mid = next; - if (next && next->vm_end == end) /* cases 6, 7, 8 */ + if (next) + vma_write_lock(next); + if (next && next->vm_end == end) { /* cases 6, 7, 8 */ next = find_vma(mm, next->vm_end); + if (next) + vma_write_lock(next); + } /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); @@ -2198,6 +2208,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, int err; validate_mm_mt(mm); + vma_write_lock(vma); if (vma->vm_ops && vma->vm_ops->may_split) { err = vma->vm_ops->may_split(vma, addr); if (err) @@ -2564,6 +2575,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Attempt to expand an old mapping */ /* Check next */ + if (next) + vma_write_lock(next); if (next && next->vm_start == end && !vma_policy(next) && can_vma_merge_before(next, vm_flags, NULL, file, pgoff+pglen, NULL_VM_UFFD_CTX, NULL)) { @@ -2573,6 +2586,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, } /* Check prev */ + if (prev) + vma_write_lock(prev); if (prev && prev->vm_end == addr && !vma_policy(prev) && (vma ? can_vma_merge_after(prev, vm_flags, vma->anon_vma, file, pgoff, vma->vm_userfaultfd_ctx, NULL) : @@ -2942,6 +2957,8 @@ static int do_brk_flags(struct ma_state *mas, struct vm_area_struct *vma, if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) return -ENOMEM; + if (vma) + vma_write_lock(vma); /* * Expand the existing vma if possible; Note that singular lists do not * occur after forking, so the expand will only happen on new VMAs. -- 2.39.0