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Wed, 15 Feb 2023 21:18:33 -0800 (PST) Date: Wed, 15 Feb 2023 21:17:31 -0800 In-Reply-To: <20230216051750.3125598-1-surenb@google.com> Mime-Version: 1.0 References: <20230216051750.3125598-1-surenb@google.com> X-Mailer: git-send-email 2.39.1.581.gbfd45094c4-goog Message-ID: <20230216051750.3125598-17-surenb@google.com> Subject: [PATCH v3 16/35] 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, paulmck@kernel.org, mingo@redhat.com, will@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, chriscli@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, leewalsh@google.com, posk@google.com, michalechner92@googlemail.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, Suren Baghdasaryan X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: D59B340004 X-Stat-Signature: gwrrr63p1fduakadh4rwqmaja1s8eabp X-HE-Tag: 1676524714-707954 X-HE-Meta: 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 Rn8dA0lE 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 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: 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. 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 c5f2ddf17b87..ec2f8d0af280 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -269,8 +269,11 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) */ vma_iter_init(&vmi, mm, oldbrk); next = vma_find(&vmi, newbrk + PAGE_SIZE + stack_guard_gap); - if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) - goto out; + if (next) { + vma_start_write(next); + if (newbrk + PAGE_SIZE > vm_start_gap(next)) + goto out; + } brkvma = vma_prev_limit(&vmi, mm->start_brk); /* Ok, looks good - let it rip. */ @@ -912,10 +915,17 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, if (vm_flags & VM_SPECIAL) return NULL; + if (prev) + vma_start_write(prev); next = find_vma(mm, prev ? prev->vm_end : 0); + if (next) + vma_start_write(next); mid = next; - if (next && next->vm_end == end) /* cases 6, 7, 8 */ + if (next && next->vm_end == end) { /* cases 6, 7, 8 */ next = find_vma(mm, next->vm_end); + if (next) + vma_start_write(next); + } /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); @@ -2163,6 +2173,7 @@ int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, WARN_ON(vma->vm_start >= addr); WARN_ON(vma->vm_end <= addr); + vma_start_write(vma); if (vma->vm_ops && vma->vm_ops->may_split) { err = vma->vm_ops->may_split(vma, addr); if (err) @@ -2518,6 +2529,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Attempt to expand an old mapping */ /* Check next */ + if (next) + vma_start_write(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)) { @@ -2527,6 +2540,8 @@ unsigned long mmap_region(struct file *file, unsigned long addr, } /* Check prev */ + if (prev) + vma_start_write(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) : @@ -2900,6 +2915,8 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma, if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) return -ENOMEM; + if (vma) + vma_start_write(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.