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[95.114.33.154]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-486eb36e4a6sm9132172f8f.37.2026.09.11.15.49.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Sep 2026 15:49:26 -0700 (PDT) Date: Sat, 12 Sep 2026 00:48:54 +0200 From: Karl Mehltretter To: "Michael S. Tsirkin" Cc: virtualization@lists.linux.dev, jasowangio@gmail.com, eperezma@redhat.com, xuanzhuo@linux.alibaba.com, jiri@resnulli.us, sashiko-bot@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/3] virtio_pci_modern: move avq cleanup from reset to del_vqs Message-ID: References: Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Sep 11, 2026 at 05:20:15PM +0100, Michael S. Tsirkin wrote: > New in v3. v2 dropped sync from modern vp_reset in one combined > patch, leaving avq_cleanup in vp_reset. v3 moves avq_cleanup out > of vp_reset entirely into vp_del_vqs, fixing the race. Adds NULL > check for admin_vq.info for find_vqs error paths. > I think patch 3 introduces a use-after-free in the MSI-X setup error path. With VP_VQ_VECTOR_POLICY_EACH, vp_setup_vq() stores the admin queue's info pointer before request_irq(). If request_irq() fails, vp_del_vq() frees info but leaves admin_vq.info set. vp_find_vqs_msix() then calls vp_del_vqs(). vp_del_vqs() now calls vp_modern_avq_cleanup() first and dereferences the freed pointer: vq = vp_dev->admin_vq.info->vq; No interrupt needs to fire. I reproduced this on v3 with KASAN by returning -ENOMEM only for the admin queue's request_irq(): BUG: KASAN: slab-use-after-free in vp_modern_avq_cleanup+0xf4/0x110 KASAN shows the allocation in vp_setup_vq(), the free in vp_find_one_vq_msix(), and the access in vp_modern_avq_cleanup(). Adding *p_info = NULL after vp_del_vq() made the same test fall back and boot without a KASAN report. Thanks, Karl