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Howlett" Cc: Suren Baghdasaryan , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes , Shakeel Butt , Jann Horn , stable@vger.kernel.org, syzbot+131f9eb2b5807573275c@syzkaller.appspotmail.com Subject: Re: [PATCH] mm/mmap_lock: Reset maple state on lock_vma_under_rcu() retry Message-Id: <20251112122446.e1f2c037550dc591a4d6b307@linux-foundation.org> In-Reply-To: References: <20251111215605.1721380-1-Liam.Howlett@oracle.com> <8219599b-941e-4ffd-875f-6548e217c16c@suse.cz> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 212AC180002 X-Stat-Signature: ajgr3n7wwcy5j5hpwectcnpoyy5xygbg X-Rspam-User: X-HE-Tag: 1762979088-962766 X-HE-Meta: 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 E5i/pM2I EYvDUGCbaAaTdY1oWtPvrJ6QruBd9g8K9cng126d0EZzMch2BnnW1yS4AP4LDbG2O83sxMjVYYtABzle7zyp2oo0B/+fR2FJMPS9K 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 Tue, 11 Nov 2025 21:18:19 -0500 "Liam R. Howlett" wrote: > > Prior to commit 0b16f8bed19c ("mm: change vma_start_read() to drop RCU > > lock on failure"), vma_start_read() would drop rcu read lock and > > return NULL, so the retry would not have happened. However, now that > > vma_start_read() drops rcu read lock on failure followed by a retry, > > we may end up using a freed maple tree node cached in the maple state. > > Yes, sounds good. > > Andrew, can you make this change and also drop Cc stable tag? Done. > This needs to be a hot fix, as Vlastimil said earlier. Yup.