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Mon, 26 Oct 2026 18:17:41 -0700 (PDT) From: Ritesh Harjani (IBM) To: Bart Van Assche , Madhavan Srinivasan Cc: Michael Ellerman , Nicholas Piggin , Christophe Leroy , Shrikanth Hegde , Qian Cai , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Bart Van Assche Subject: Re: [PATCH] powerpc/iommu: Fix an RCU read lock leak in mm_iommu_is_devmem() In-Reply-To: <56f0c45723ee53149a21ceb599010e957457afd8.1793044370.git.bvanassche@acm.org> Date: Tue, 27 Oct 2026 06:43:59 +0530 Message-ID: References: <56f0c45723ee53149a21ceb599010e957457afd8.1793044370.git.bvanassche@acm.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Bart Van Assche writes: > mm_iommu_is_devmem() returns true from inside its RCU read-side > critical section without calling rcu_read_unlock(). Neither caller, > iommu_tce_xchg_no_kill() nor tce_page_is_contained(), drops the RCU > read lock, so every successful lookup leaks one RCU read lock. Fix this > by calling rcu_read_unlock() before returning true. The pointer to the > list element is not used after the RCU read lock is dropped. > > Fixes: b5952f8125ae ("powerpc/mm/book3s64/iommu: fix some RCU-list locks") Thanks Bart, but this was caught as part of Clang's context analysis work on powerpc. It is already posted here [1]. Could you review that instead? [1]: https://lore.kernel.org/linuxppc-dev/04e4dafde56fe4b055fbd763dc0e119862073c6d.1790590014.git.ritesh.list@gmail.com/ -ritesh