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[95.21.2.212]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48b380fac3csm138889f8f.21.2026.10.01.11.43.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Oct 2026 11:43:32 -0700 (PDT) From: =?UTF-8?q?=C3=93scar=20Meg=C3=ADa=20L=C3=B3pez?= To: Dave Airlie , Gerd Hoffmann Cc: =?UTF-8?q?=C3=93scar=20Meg=C3=ADa=20L=C3=B3pez?= , virtualization@lists.linux.dev, spice-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev Subject: [PATCH v5] drm/qxl: fix use-after-free in qxl_irq_handler on PCI Date: Thu, 1 Oct 2026 20:43:18 +0200 Message-ID: <20261001184321.80615-1-megia.oscar@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Executing below script: i=0;\ while [ 1 -eq 1 ]; do\ i=$((i+1)); echo 0000:00:01.0 > /sys/bus/pci/drivers/qxl/unbind;\ if (($i%1000==0)); then\ echo loops=$i; free;\ grep nr_free_pages /proc/vmstat;\ grep -E "VmallocUsed|Slab|Reclaimable|SUnreclaim" /proc/meminfo;\ sync; echo 3 > /proc/sys/vm/drop_caches;\ echo 1 > /proc/sys/vm/compact_memory;\ udevadm settle;\ free;\ grep nr_free_pages /proc/vmstat;\ grep -E "VmallocUsed|Slab|Reclaimable|SUnreclaim" /proc/meminfo;\ uptime;\ fi;\ echo 0000:00:01.0 > /sys/bus/pci/drivers/qxl/bind;\ done After a few seconds, it reports: ================================================================== BUG: KASAN: slab-use-after-free in qxl_irq_handler+0x269/0x2b0 Read of size 8 at addr ffff888001c6cd48 by task swapper/0/0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.1.0-10963-g1a3746ccbb0a #31 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Arch Linux 1.17.0-2-2 04/01/2014 Call Trace: dump_stack_lvl+0x4d/0x70 print_report+0x14b/0x4b0 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? profile_tick+0x56/0x90 ? tick_nohz_handler+0x23c/0x5c0 kasan_report+0x117/0x140 ? qxl_irq_handler+0x269/0x2b0 ? qxl_irq_handler+0x269/0x2b0 ? __pfx_qxl_irq_handler+0x10/0x10 qxl_irq_handler+0x269/0x2b0 ? __pfx_qxl_irq_handler+0x10/0x10 ? __pfx_qxl_irq_handler+0x10/0x10 __handle_irq_event_percpu+0x116/0x450 ? __pfx__raw_spin_lock+0x10/0x10 handle_irq_event+0xa6/0x1c0 handle_fasteoi_irq+0x271/0xb10 ? __pfx_handle_fasteoi_irq+0x10/0x10 __common_interrupt+0x60/0x130 common_interrupt+0x7a/0x90 asm_common_interrupt+0x26/0x40 RIP: 0010:pv_native_safe_halt+0xf/0x20 Code: 42 de 00 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d a3 cf 20 00 fb f4 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90 RSP: 0018:ffffffffb8207e48 EFLAGS: 00000206 RAX: ffff8880b296f000 RBX: ffffffffb82146c0 RCX: 0000000000000001 RDX: 0000000000000001 RSI: 0000000000000004 RDI: 0000000000067a04 RBP: fffffbfff70428d8 R08: ffffffffb7247e1d R09: 1ffff1100d846202 R10: ffffed100d846203 R11: ffffed100d846203 R12: 0000000000000000 R13: 0000000000000000 R14: 1ffffffff7040fcd R15: dffffc0000000000 ? ct_kernel_exit.constprop.0+0x9d/0xc0 default_idle+0x9/0x10 default_idle_call+0x37/0x60 do_idle+0x3a8/0x5d0 ? __pfx___schedule+0x10/0x10 ? __pfx_do_idle+0x10/0x10 cpu_startup_entry+0x4e/0x60 rest_init+0x11a/0x120 start_kernel+0x382/0x390 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0xd6/0xe0 common_startup_64+0x13e/0x158 in v4, disable_irq() was introduced, but because qxl requests its IRQ with IRQF_SHARED, calling disable_irq() masks the interrupt line globally at the controller level (IO-APIC), potentially hanging other devices sharing the same line (e.g., virtio devices). Furthermore, placing free_irq() too early caused hardware teardown timeouts (e.g., waiting on qdev->release_event in qxl_device_fini()). Fix this by: 1. Masking interrupts specifically on the QXL hardware via ram_header->int_mask = 0 and flushing pending work before calling free_irq(). 2. Placing qxl_irq_fini() in qxl_pci_remove() after drm_atomic_helper_shutdown() so completion events are handled during atomic shutdown, but before releasing legacy VGA resources and device structures. Assisted-by: OpenCode:1.17.13-Big Pickle/DeepSeek V4 Flash Fixes: 48bd85808443 ("drm/qxl: Convert to Linux IRQ interfaces") Signed-off-by: Óscar Megía López --- Changes in v2: - Updated qxl_ttm_init to add ttm_device_fini on error in qxl_ttm_init_mem_type. Changes in v3: - Added free_irq on qxl_probe unload. - Set to NULL after free on qxl_device_fini and added idr_destroy on release_idr and surf_id_idr. - Free client_monitors_config. Changes in v4: - Delete all code unnecessary. Leave only code to fix the BUG. Changes in v5: - Replace disable_irq() with device-specific interrupt masking via qdev->ram_header->int_mask = 0 to prevent global masking on IRQF_SHARED lines. - Reorder qxl_irq_fini() call in qxl_pci_remove() to ensure hardware teardown events (like release_event in qxl_device_fini) complete before free_irq(). --- drivers/gpu/drm/qxl/qxl_drv.c | 2 ++ drivers/gpu/drm/qxl/qxl_drv.h | 1 + drivers/gpu/drm/qxl/qxl_irq.c | 13 +++++++++++++ 3 files changed, 16 insertions(+) diff --git a/drivers/gpu/drm/qxl/qxl_drv.c b/drivers/gpu/drm/qxl/qxl_drv.c index 1e6a2392d7c6..3ec2f9395439 100644 --- a/drivers/gpu/drm/qxl/qxl_drv.c +++ b/drivers/gpu/drm/qxl/qxl_drv.c @@ -154,10 +154,12 @@ static void qxl_pci_remove(struct pci_dev *pdev) { struct drm_device *dev = pci_get_drvdata(pdev); + struct qxl_device *qdev = to_qxl(dev); drm_kms_helper_poll_fini(dev); drm_dev_unregister(dev); drm_atomic_helper_shutdown(dev); + qxl_irq_fini(qdev); if (pci_is_vga(pdev) && pdev->revision < 5) vga_put(pdev, VGA_RSRC_LEGACY_IO); } diff --git a/drivers/gpu/drm/qxl/qxl_drv.h b/drivers/gpu/drm/qxl/qxl_drv.h index cc02b5f10ad9..e8598fdbe886 100644 --- a/drivers/gpu/drm/qxl/qxl_drv.h +++ b/drivers/gpu/drm/qxl/qxl_drv.h @@ -424,6 +424,7 @@ void qxl_gem_prime_vunmap(struct drm_gem_object *obj, /* qxl_irq.c */ int qxl_irq_init(struct qxl_device *qdev); +void qxl_irq_fini(struct qxl_device *qdev); void qxl_debugfs_add_files(struct qxl_device *qdev, struct drm_info_list *files, diff --git a/drivers/gpu/drm/qxl/qxl_irq.c b/drivers/gpu/drm/qxl/qxl_irq.c index 4018bcf808e5..9d2311b15660 100644 --- a/drivers/gpu/drm/qxl/qxl_irq.c +++ b/drivers/gpu/drm/qxl/qxl_irq.c @@ -105,3 +105,16 @@ int qxl_irq_init(struct qxl_device *qdev) } return 0; } + +void qxl_irq_fini(struct qxl_device *qdev) +{ + struct drm_device *ddev = &qdev->ddev; + struct pci_dev *pdev = to_pci_dev(ddev->dev); + + if (qdev->ram_header) + qdev->ram_header->int_mask = 0; + + cancel_work_sync(&qdev->client_monitors_config_work); + + free_irq(pdev->irq, ddev); +} -- 2.55.0