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Tue, 22 Sep 2026 00:22:02 -0700 (PDT) From: Yuchao Zhang To: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= , Juergen Gross , Stefano Stabellini , Jens Axboe Cc: Oleksandr Tyshchenko , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yuchao Zhang Subject: [PATCH v2] xen-blkfront: unbind irq before tearing down ring and shadow requests Date: Tue, 22 Sep 2026 15:21:55 +0800 Message-ID: <20260922072155.34625-1-ndaugoing@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In blkif_free_ring(), the driver tears down the ring's persistent grants, shadow request arrays, and shared ring structure (xenbus_teardown_ring), and only calls unbind_from_irqhandler() at the very end. While blkif_free_ring() is freeing persistent grants and clearing the shadow array, the event channel interrupt (blkif_interrupt) is still registered and active. If an interrupt arrives from the backend during this teardown window, blkif_interrupt() reads rinfo->ring.sring and, via blkif_completion(), accesses rinfo->shadow[id].grants_used and rinfo->shadow[id].sg. blkif_free_ring() tears these structures down without holding rinfo->ring_lock, and the handler only checks info->connected at entry, so this is a real race resulting in a use-after-free or NULL pointer dereference. Fix this by moving unbind_from_irqhandler() to the beginning of blkif_free_ring(). Calling unbind_from_irqhandler() first frees the IRQ and synchronizes with any in-flight interrupt handlers on other CPUs before ring memory and shadow request structures are deallocated, matching the teardown order in drivers/net/xen-netfront.c. Fixes: 11659569f720 ("xen/blkfront: split per device io_lock") Cc: stable@vger.kernel.org Signed-off-by: Yuchao Zhang --- v2: - Update Fixes tag to 11659569f720 ("xen/blkfront: split per device io_lock") per Roger Pau Monné. - Add comment in blkif_free_ring() noting that interrupt teardown must precede freeing queue-related data. drivers/block/xen-blkfront.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 8dad7bf5f664..86f5dd3aced1 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1210,6 +1210,14 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo) struct blkfront_info *info = rinfo->dev_info; int i, j, segs; + /* + * Interrupt teardown must be done ahead of freeing queue-related + * data, otherwise the interrupt handler can race with the cleanup. + */ + if (rinfo->irq) + unbind_from_irqhandler(rinfo->irq, rinfo); + rinfo->evtchn = rinfo->irq = 0; + /* * Remove indirect pages, this only happens when using indirect * descriptors but not persistent grants @@ -1292,10 +1300,6 @@ static void blkif_free_ring(struct blkfront_ring_info *rinfo) /* Free resources associated with old device channel. */ xenbus_teardown_ring((void **)&rinfo->ring.sring, info->nr_ring_pages, rinfo->ring_ref); - - if (rinfo->irq) - unbind_from_irqhandler(rinfo->irq, rinfo); - rinfo->evtchn = rinfo->irq = 0; } static void blkif_free(struct blkfront_info *info, int suspend) -- 2.53.0