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[159.2.73.22]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8d2a8648c17sm1169709885a.33.2026.04.06.15.17.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Apr 2026 15:17:44 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1w9sGN-0000000E50y-3Hgv; Mon, 06 Apr 2026 19:17:43 -0300 Date: Mon, 6 Apr 2026 19:17:43 -0300 From: Jason Gunthorpe To: Sina Hassani Cc: kevin.tian@intel.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Aaron Wisner , stable@vger.kernel.org Subject: Re: [PATCH] Fixes a race in iopt_unmap_iova_range Message-ID: <20260406221743.GI2551565@ziepe.ca> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Apr 06, 2026 at 03:00:36PM -0700, Sina Hassani wrote: > Bug: iopt_unmap_iova_range releases the lock on iova_rwsem inside the loop > body when getting to the more expensive unmap operations. This is fine on > its own except the loop condition is based on the first area that matches > the unmap address range. If a concurrent call to map picks an area that was > unmapped in the previous iterations, this loop will try to mistakenly unmap > them. Does this mean you are also using the automatic IOVA allocator? It is certainly an error for userspace to be mapping to IOVA that is under concurrent unmap. > io_pagetable *iopt, unsigned long start, > iopt_put_pages(pages); > > unmapped_bytes += area_last - area_first + 1; > + start = area_last + 1; This seems like a reasonable solution, but area_last + 1 can overflow and that needs to be delt with too. /* Do not reconsider things already unmapped in case of concurrent allocation */ if (area_last != last) start = area_last + 1; ? Jason