We report a bug (in linux-5.6.11) found by FuzzUSB (a modified version of syzkaller) The buf of an usbtest_dev instance (dev->buf) allocated in usbtest_probe() leaked. The usbtest_dev instance holding the buf is attached to a corresponding device instance through usb_set_intfdata(). But later, the usbtest_dev instance seems to be freed without deallocating its buf field ahead. kernel config: https://kt0755.github.io/etc/config_v5.6.11 ================================================================== BUG: memory leak unreferenced object 0xffff888055046e00 (size 256): comm "kworker/2:9", pid 2570, jiffies 4294942129 (age 1095.500s) hex dump (first 32 bytes): 00 70 04 55 80 88 ff ff 18 bb 5a 81 ff ff ff ff .p.U......Z..... f5 96 78 81 ff ff ff ff 37 de 8e 81 ff ff ff ff ..x.....7....... backtrace: [<00000000d121dccf>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline] [<00000000d121dccf>] slab_post_alloc_hook mm/slab.h:586 [inline] [<00000000d121dccf>] slab_alloc_node mm/slub.c:2786 [inline] [<00000000d121dccf>] slab_alloc mm/slub.c:2794 [inline] [<00000000d121dccf>] kmem_cache_alloc_trace+0x15e/0x2d0 mm/slub.c:2811 [<000000005c3c3381>] kmalloc include/linux/slab.h:555 [inline] [<000000005c3c3381>] usbtest_probe+0x286/0x19d0 drivers/usb/misc/usbtest.c:2790 [<000000001cec6910>] usb_probe_interface+0x2bd/0x870 drivers/usb/core/driver.c:361 [<000000007806c118>] really_probe+0x48d/0x8f0 drivers/base/dd.c:551 [<00000000a3308c3e>] driver_probe_device+0xfc/0x2a0 drivers/base/dd.c:724 [<000000003ef66004>] __device_attach_driver+0x1b6/0x240 drivers/base/dd.c:831 [<00000000eee53e97>] bus_for_each_drv+0x14e/0x1e0 drivers/base/bus.c:431 [<00000000bb0648d0>] __device_attach+0x1f9/0x350 drivers/base/dd.c:897 [<00000000838b324a>] device_initial_probe+0x1a/0x20 drivers/base/dd.c:944 [<0000000030d501c1>] bus_probe_device+0x1e1/0x280 drivers/base/bus.c:491 [<000000005bd7adef>] device_add+0x131d/0x1c40 drivers/base/core.c:2504 [<00000000a0937814>] usb_set_configuration+0xe84/0x1ab0 drivers/usb/core/message.c:2030 [<00000000e3934741>] generic_probe+0x6a/0xe0 drivers/usb/core/generic.c:210 [<0000000098ade0f1>] usb_probe_device+0x90/0xd0 drivers/usb/core/driver.c:266 [<000000007806c118>] really_probe+0x48d/0x8f0 drivers/base/dd.c:551 [<00000000a3308c3e>] driver_probe_device+0xfc/0x2a0 drivers/base/dd.c:724 ==================================================================
