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([2405:201:682f:383f:53b2:c8c7:f2ef:3f4d]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3267c388e26sm11654561eec.22.2026.08.17.20.36.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 20:36:58 -0700 (PDT) From: Deepanshu Kartikey To: jgg@ziepe.ca, kevin.tian@intel.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com Cc: steven.sistare@oracle.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+48637757323884de77a2@syzkaller.appspotmail.com Subject: [PATCH] iommufd: Fix NULL deref of area->pages in ioas_change_process Date: Tue, 18 Aug 2026 09:06:50 +0530 Message-Id: <20260818033650.21443-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Areas are inserted into the area_itree before area->pages is assigned, so an area with a NULL pages pointer is briefly visible to readers. iommufd_ioas_change_process() walks every area and dereferences area->pages unconditionally, which oopses when racing with a concurrent IOMMU_IOAS_MAP_FILE. Reject the racing case with -EBUSY, matching how iopt_unmap_iova_range() handles the same window. Checking in the first loop covers the whole function since all iova_rwsems are held for write across the call. Fixes: 829ed626499c ("iommufd: Add IOMMU_IOAS_CHANGE_PROCESS") Reported-by: syzbot+48637757323884de77a2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=48637757323884de77a2 Tested-by: syzbot+48637757323884de77a2@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- drivers/iommu/iommufd/ioas.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/iommu/iommufd/ioas.c b/drivers/iommu/iommufd/ioas.c index fed06c2b728e..71bffece84b5 100644 --- a/drivers/iommu/iommufd/ioas.c +++ b/drivers/iommu/iommufd/ioas.c @@ -535,6 +535,10 @@ int iommufd_ioas_change_process(struct iommufd_ucmd *ucmd) return rc; for_each_ioas_area(&ioas_list, index, ioas, area) { + if (!area->pages) { + rc = -EBUSY; + goto out; + } if (area->pages->type != IOPT_ADDRESS_FILE) { rc = -EINVAL; goto out; -- 2.34.1