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([2405:4802:1d4a:e90:f072:2258:ced5:5d8c]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2df6a516d96sm12825075ad.2.2026.09.23.08.07.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 08:07:59 -0700 (PDT) From: Nguyen Ngoc Thang To: Thomas Winischhofer , Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Nguyen Ngoc Thang , syzbot+109061940215dd4b011e@syzkaller.appspotmail.com Subject: [PATCH] usb: sisusbvga: stop early init on the first failed transfer Date: Wed, 23 Sep 2026 22:07:53 +0700 Message-ID: <20260923150754.31652-1-ngocthang2710.1999@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit sisusb_probe() initializes the graphics device from within the hub's enumeration work, i.e. with the parent hub's device lock held. sisusb_do_init_gfxdevice() accumulates errors with "ret |=" and keeps going after a failed transfer. If the device does not answer, every remaining transfer sits out its full timeout (5s, retried 6 times), so probe holds the hub lock for ~30s per access and about 10 minutes in total. Anything that needs that lock, such as usbdev_open() and usbdev_ioctl() on the root hub, is blocked for the duration and trips the hung task detector. Return on the first error instead. Also fold the three identical BAR setup sequences into a helper and the leading magic writes into a table. The sequence of accesses is unchanged when the device responds. Reproduced with a raw-gadget device (0711:0550, six bulk endpoints that never complete I/O) on dummy_hcd: opening the root hub blocked for 603s before, 29s after. Reported-by: syzbot+109061940215dd4b011e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=109061940215dd4b011e Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Nguyen Ngoc Thang --- Notes (not for the commit log): I have no SiS USB2VGA hardware, so the reordering is verified by inspection only. A single silent device can still hold the hub lock for ~30s (one failed transfer); removing that entirely would mean moving init out of probe. Happy to do that if you prefer. drivers/usb/misc/sisusbvga/sisusbvga.c | 120 +++++++++++++------------ 1 file changed, 62 insertions(+), 58 deletions(-) diff --git a/drivers/usb/misc/sisusbvga/sisusbvga.c b/drivers/usb/misc/sisusbvga/sisusbvga.c index 3e75a7c24828..544284111191 100644 --- a/drivers/usb/misc/sisusbvga/sisusbvga.c +++ b/drivers/usb/misc/sisusbvga/sisusbvga.c @@ -2064,77 +2064,81 @@ static void sisusb_get_ramconfig(struct sisusb_usb_data *sisusb) ram_datarate[ramtype], ram_dynamictype[ramtype], bw); } +/* Probe BAR size, then map it at @base */ +static int sisusb_init_bar(struct sisusb_usb_data *sisusb, int regnum, u32 base) +{ + u32 tmp32; + int ret; + + ret = sisusb_read_pci_config(sisusb, regnum, &tmp32); + if (ret) + return ret; + ret = sisusb_write_pci_config(sisusb, regnum, 0xfffffff0); + if (ret) + return ret; + ret = sisusb_read_pci_config(sisusb, regnum, &tmp32); + if (ret) + return ret; + return sisusb_write_pci_config(sisusb, regnum, (tmp32 & 0x0f) | base); +} + +/* Bail out on the first failure: each access to a dead device takes 5s */ static int sisusb_do_init_gfxdevice(struct sisusb_usb_data *sisusb) { + static const struct { u32 address, data; } magic[] = { + { 0x00000324, 0x00000004 }, + { 0x00000364, 0x00000004 }, + { 0x00000384, 0x00000004 }, + { 0x00000100, 0x00000700 }, + }; + static const struct { int regnum; u32 base; } bars[] = { + { 0x10, SISUSB_PCI_MEMBASE }, + { 0x14, SISUSB_PCI_MMIOBASE }, + { 0x18, SISUSB_PCI_IOPORTBASE }, + }; struct sisusb_packet packet; - int ret; + int ret, i; u32 tmp32; /* Do some magic */ - packet.header = 0x001f; - packet.address = 0x00000324; - packet.data = 0x00000004; - ret = sisusb_send_bridge_packet(sisusb, 10, &packet, 0); - - packet.header = 0x001f; - packet.address = 0x00000364; - packet.data = 0x00000004; - ret |= sisusb_send_bridge_packet(sisusb, 10, &packet, 0); - - packet.header = 0x001f; - packet.address = 0x00000384; - packet.data = 0x00000004; - ret |= sisusb_send_bridge_packet(sisusb, 10, &packet, 0); - - packet.header = 0x001f; - packet.address = 0x00000100; - packet.data = 0x00000700; - ret |= sisusb_send_bridge_packet(sisusb, 10, &packet, 0); + for (i = 0; i < ARRAY_SIZE(magic); i++) { + packet.header = 0x001f; + packet.address = magic[i].address; + packet.data = magic[i].data; + ret = sisusb_send_bridge_packet(sisusb, 10, &packet, 0); + if (ret) + return ret; + } packet.header = 0x000f; packet.address = 0x00000004; - ret |= sisusb_send_bridge_packet(sisusb, 6, &packet, 0); + ret = sisusb_send_bridge_packet(sisusb, 6, &packet, 0); + if (ret) + return ret; packet.data |= 0x17; - ret |= sisusb_send_bridge_packet(sisusb, 10, &packet, 0); - - /* Init BAR 0 (VRAM) */ - ret |= sisusb_read_pci_config(sisusb, 0x10, &tmp32); - ret |= sisusb_write_pci_config(sisusb, 0x10, 0xfffffff0); - ret |= sisusb_read_pci_config(sisusb, 0x10, &tmp32); - tmp32 &= 0x0f; - tmp32 |= SISUSB_PCI_MEMBASE; - ret |= sisusb_write_pci_config(sisusb, 0x10, tmp32); - - /* Init BAR 1 (MMIO) */ - ret |= sisusb_read_pci_config(sisusb, 0x14, &tmp32); - ret |= sisusb_write_pci_config(sisusb, 0x14, 0xfffffff0); - ret |= sisusb_read_pci_config(sisusb, 0x14, &tmp32); - tmp32 &= 0x0f; - tmp32 |= SISUSB_PCI_MMIOBASE; - ret |= sisusb_write_pci_config(sisusb, 0x14, tmp32); - - /* Init BAR 2 (i/o ports) */ - ret |= sisusb_read_pci_config(sisusb, 0x18, &tmp32); - ret |= sisusb_write_pci_config(sisusb, 0x18, 0xfffffff0); - ret |= sisusb_read_pci_config(sisusb, 0x18, &tmp32); - tmp32 &= 0x0f; - tmp32 |= SISUSB_PCI_IOPORTBASE; - ret |= sisusb_write_pci_config(sisusb, 0x18, tmp32); - - /* Enable memory and i/o access */ - ret |= sisusb_read_pci_config(sisusb, 0x04, &tmp32); - tmp32 |= 0x3; - ret |= sisusb_write_pci_config(sisusb, 0x04, tmp32); + ret = sisusb_send_bridge_packet(sisusb, 10, &packet, 0); + if (ret) + return ret; - if (ret == 0) { - /* Some further magic */ - packet.header = 0x001f; - packet.address = 0x00000050; - packet.data = 0x000000ff; - ret |= sisusb_send_bridge_packet(sisusb, 10, &packet, 0); + for (i = 0; i < ARRAY_SIZE(bars); i++) { + ret = sisusb_init_bar(sisusb, bars[i].regnum, bars[i].base); + if (ret) + return ret; } - return ret; + /* Enable memory and i/o access */ + ret = sisusb_read_pci_config(sisusb, 0x04, &tmp32); + if (ret) + return ret; + ret = sisusb_write_pci_config(sisusb, 0x04, tmp32 | 0x3); + if (ret) + return ret; + + /* Some further magic */ + packet.header = 0x001f; + packet.address = 0x00000050; + packet.data = 0x000000ff; + return sisusb_send_bridge_packet(sisusb, 10, &packet, 0); } /* Initialize the graphics device (return 0 on success) -- 2.43.0