We report a bug (in linux-5.5.11) found by FuzzUSB (a modified version of syzkaller) In function usb_hcd_unlink_urb (driver/usb/core/hcd.c:1607), it tries to read "urb->use_count". But it seems the instance "urb" was already freed (right after urb->dev at line 1597) by the function "urb_destroy" in a different thread, which caused memory access violation. To solve, it may need to check if urb is valid before urb->use_count, to avoid such freed memory access. kernel config: https://kt0755.github.io/etc/config_v5.5.11 ================================================================== BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:26 [inline] BUG: KASAN: use-after-free in usb_hcd_unlink_urb+0x5f/0x170 drivers/usb/core/hcd.c:1607 Read of size 4 at addr ffff888065379610 by task kworker/u4:1/27 CPU: 1 PID: 27 Comm: kworker/u4:1 Not tainted 5.5.11 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Workqueue: scsi_tmf_2 scmd_eh_abort_handler Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xce/0x128 lib/dump_stack.c:118 print_address_description.constprop.4+0x21/0x3c0 mm/kasan/report.c:374 __kasan_report+0x153/0x1cb mm/kasan/report.c:506 kasan_report+0x12/0x20 mm/kasan/common.c:639 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x152/0x1b0 mm/kasan/generic.c:192 __kasan_check_read+0x11/0x20 mm/kasan/common.c:95 atomic_read include/asm-generic/atomic-instrumented.h:26 [inline] usb_hcd_unlink_urb+0x5f/0x170 drivers/usb/core/hcd.c:1607 usb_unlink_urb+0x72/0xb0 drivers/usb/core/urb.c:657 usb_sg_cancel+0x14e/0x290 drivers/usb/core/message.c:602 usb_stor_stop_transport+0x5e/0xa0 drivers/usb/storage/transport.c:937 command_abort+0x19d/0x200 drivers/usb/storage/scsiglue.c:439 scsi_try_to_abort_cmd drivers/scsi/scsi_error.c:927 [inline] scmd_eh_abort_handler+0x18e/0x410 drivers/scsi/scsi_error.c:145 process_one_work+0x9dd/0x1710 kernel/workqueue.c:2266 worker_thread+0x8b/0xc40 kernel/workqueue.c:2412 kthread+0x35f/0x440 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Allocated by task 2532: save_stack+0x21/0x90 mm/kasan/common.c:72 set_track mm/kasan/common.c:80 [inline] __kasan_kmalloc.constprop.3+0xa7/0xd0 mm/kasan/common.c:513 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527 __kmalloc+0x148/0x380 mm/slub.c:3812 kmalloc include/linux/slab.h:561 [inline] usb_alloc_urb+0x42/0x90 drivers/usb/core/urb.c:74 usb_sg_init+0x323/0xa00 drivers/usb/core/message.c:406 usb_stor_bulk_transfer_sglist+0xbe/0x280 drivers/usb/storage/transport.c:423 usb_stor_bulk_srb+0x10d/0x230 drivers/usb/storage/transport.c:465 usb_stor_Bulk_transport+0x55f/0x1060 drivers/usb/storage/transport.c:1161 usb_stor_invoke_transport+0xef/0x15f0 drivers/usb/storage/transport.c:606 usb_stor_transparent_scsi_command+0x1d/0x30 drivers/usb/storage/protocol.c:108 usb_stor_control_thread+0x6d8/0xa80 drivers/usb/storage/usb.c:380 kthread+0x35f/0x440 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Freed by task 2532: save_stack+0x21/0x90 mm/kasan/common.c:72 set_track mm/kasan/common.c:80 [inline] kasan_set_free_info mm/kasan/common.c:335 [inline] __kasan_slab_free+0x135/0x190 mm/kasan/common.c:474 kasan_slab_free+0xe/0x10 mm/kasan/common.c:483 slab_free_hook mm/slub.c:1425 [inline] slab_free_freelist_hook mm/slub.c:1458 [inline] slab_free mm/slub.c:3005 [inline] kfree+0xf7/0x410 mm/slub.c:3966 urb_destroy drivers/usb/core/urb.c:26 [inline] kref_put include/linux/kref.h:65 [inline] usb_free_urb.part.0+0x95/0x100 drivers/usb/core/urb.c:96 usb_free_urb+0x1f/0x30 drivers/usb/core/urb.c:95 sg_clean+0x111/0x270 drivers/usb/core/message.c:263 usb_sg_wait+0x26d/0x440 drivers/usb/core/message.c:573 usb_stor_bulk_transfer_sglist+0x127/0x280 drivers/usb/storage/transport.c:447 usb_stor_bulk_srb+0x10d/0x230 drivers/usb/storage/transport.c:465 usb_stor_Bulk_transport+0x55f/0x1060 drivers/usb/storage/transport.c:1161 usb_stor_invoke_transport+0xef/0x15f0 drivers/usb/storage/transport.c:606 usb_stor_transparent_scsi_command+0x1d/0x30 drivers/usb/storage/protocol.c:108 usb_stor_control_thread+0x6d8/0xa80 drivers/usb/storage/usb.c:380 kthread+0x35f/0x440 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 The buggy address belongs to the object at ffff888065379600 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 16 bytes inside of 192-byte region [ffff888065379600, ffff8880653796c0) The buggy address belongs to the page: page:ffffea000194de40 refcount:1 mapcount:0 mapping:ffff88806c002a00 index:0x0 flags: 0x100000000000200(slab) raw: 0100000000000200 ffffea0000ee7a00 0000000500000005 ffff88806c002a00 raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888065379500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888065379580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc >ffff888065379600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888065379680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff888065379700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================
