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Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tNISC-00000002AGL-2Vbh; Mon, 16 Dec 2024 21:16:36 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id CFA4C30031E; Mon, 16 Dec 2024 22:16:35 +0100 (CET) Date: Mon, 16 Dec 2024 22:16:35 +0100 From: Peter Zijlstra To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v6 11/16] mm: enforce vma to be in detached state before freeing Message-ID: <20241216211635.GC9803@noisy.programming.kicks-ass.net> References: <20241216192419.2970941-1-surenb@google.com> <20241216192419.2970941-12-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241216192419.2970941-12-surenb@google.com> X-Stat-Signature: jtf5jtqjjo5f5gioph7619anpbecnfo9 X-Rspamd-Queue-Id: F3440A000B X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1734383762-773050 X-HE-Meta: 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 qH41Qrog YwNNlIpieHzEBGuZ6+DjXcyYiZXJqAch4ZiMSYpdRcGSFQTsvy8DKFdrDB0VUu2jVkwGAPB67cbeXxYtbT+eQI3gb/Wn83ssxNw+7zcS01Ju/LXNFbr2vZl+qCXaiw4VsTjxXqpgU/qLy/C9XQdyzqmO6XlWNDxxB2cRpJIOI/3H9BVps8gLRRGqkG+FGrq9QkBV6YB4pL4oz8V32s9PyaB6K5w== 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: On Mon, Dec 16, 2024 at 11:24:14AM -0800, Suren Baghdasaryan wrote: > exit_mmap() frees vmas without detaching them. This will become a problem > when we introduce vma reuse. Ensure that vmas are always detached before > being freed. > > Signed-off-by: Suren Baghdasaryan > --- > kernel/fork.c | 4 ++++ > mm/vma.c | 10 ++++++++-- > 2 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 283909d082cb..f1ddfc7b3b48 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -473,6 +473,10 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig) > > void __vm_area_free(struct vm_area_struct *vma) > { > +#ifdef CONFIG_PER_VMA_LOCK > + /* The vma should be detached while being destroyed. */ > + VM_BUG_ON_VMA(!is_vma_detached(vma), vma); > +#endif > vma_numab_state_free(vma); > free_anon_vma_name(vma); > kmem_cache_free(vm_area_cachep, vma); > diff --git a/mm/vma.c b/mm/vma.c > index fbd7254517d6..0436a7d21e01 100644 > --- a/mm/vma.c > +++ b/mm/vma.c > @@ -413,9 +413,15 @@ void remove_vma(struct vm_area_struct *vma, bool unreachable) > if (vma->vm_file) > fput(vma->vm_file); > mpol_put(vma_policy(vma)); > - if (unreachable) > + if (unreachable) { > +#ifdef CONFIG_PER_VMA_LOCK > + if (!is_vma_detached(vma)) { > + vma_start_write(vma); > + vma_mark_detached(vma); > + } > +#endif > __vm_area_free(vma); Again, can't you race with lockess RCU lookups?