net: usb: smsc75xx: Fix uninit-value access in __smsc75xx_read_reg

In the Linux kernel, the following vulnerability has been resolved: net: usb: smsc75xx: Fix uninit-value access in __smsc75xx_read_reg syzbot reported the following uninit-value access issue: ===================================================== BUG: KMSAN: uninit-value in smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:975 [inline] BUG: KMSAN: uninit-value in smsc75xx_bind+0x5c9/0x11e0 drivers/net/usb/smsc75xx.c:1482 CPU: 0 PID: 8696 Comm: kworker/0:3 Not tainted 5.8.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: usb_hub_wq hub_event Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x21c/0x280 lib/dump_stack.c:118 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:975 [inline] smsc75xx_bind+0x5c9/0x11e0 drivers/net/usb/smsc75xx.c:1482 usbnet_probe+0x1152/0x3f90 drivers/net/usb/usbnet.c:1737 usb_probe_interface+0xece/0x1550 drivers/usb/core/driver.c:374 really_probe+0xf20/0x20b0 drivers/base/dd.c:529 driver_probe_device+0x293/0x390 drivers/base/dd.c:701 __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807 bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431 __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873 device_initial_probe+0x4a/0x60 drivers/base/dd.c:920 bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491 device_add+0x3b0e/0x40d0 drivers/base/core.c:2680 usb_set_configuration+0x380f/0x3f10 drivers/usb/core/message.c:2032 usb_generic_driver_probe+0x138/0x300 drivers/usb/core/generic.c:241 usb_probe_device+0x311/0x490 drivers/usb/core/driver.c:272 really_probe+0xf20/0x20b0 drivers/base/dd.c:529 driver_probe_device+0x293/0x390 drivers/base/dd.c:701 __device_attach_driver+0x63f/0x830 drivers/base/dd.c:807 bus_for_each_drv+0x2ca/0x3f0 drivers/base/bus.c:431 __device_attach+0x4e2/0x7f0 drivers/base/dd.c:873 device_initial_probe+0x4a/0x60 drivers/base/dd.c:920 bus_probe_device+0x177/0x3d0 drivers/base/bus.c:491 device_add+0x3b0e/0x40d0 drivers/base/core.c:2680 usb_new_device+0x1bd4/0x2a30 drivers/usb/core/hub.c:2554 hub_port_connect drivers/usb/core/hub.c:5208 [inline] hub_port_connect_change drivers/usb/core/hub.c:5348 [inline] port_event drivers/usb/core/hub.c:5494 [inline] hub_event+0x5e7b/0x8a70 drivers/usb/core/hub.c:5576 process_one_work+0x1688/0x2140 kernel/workqueue.c:2269 worker_thread+0x10bc/0x2730 kernel/workqueue.c:2415 kthread+0x551/0x590 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 Local variable ----buf.i87@smsc75xx_bind created at: __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline] smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:968 [inline] smsc75xx_bind+0x485/0x11e0 drivers/net/usb/smsc75xx.c:1482 __smsc75xx_read_reg drivers/net/usb/smsc75xx.c:83 [inline] smsc75xx_wait_ready drivers/net/usb/smsc75xx.c:968 [inline] smsc75xx_bind+0x485/0x11e0 drivers/net/usb/smsc75xx.c:1482 This issue is caused because usbnet_read_cmd() reads less bytes than requested (zero byte in the reproducer). In this case, 'buf' is not properly filled. This patch fixes the issue by returning -ENODATA if usbnet_read_cmd() reads less bytes than requested.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于usbnet_read_cmd()读取的字节数少于请求的字节数。

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