Besides, the 'refcount bug in cdev_del' bug still exists too. Here is the detailed information: commit: 5e46d1b78a03d52306f21f77a4e4a144b6d31486 version: Linux 5.12-rc5 git tree: upstream kernel config (KASAN not enabled) and reproducing program can be found in the attachment. Report: ------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 8923 at lib/refcount.c:28 refcount_warn_saturate+0x1cf/0x210 -origin/lib/refcount.c:28 Modules linked in: CPU: 1 PID: 8923 Comm: executor Not tainted 5.12.0-rc5+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1cf/0x210 -origin/lib/refcount.c:28 Code: 4f ff ff ff e8 32 fa b5 fe 48 c7 c7 3d f8 f6 86 e8 d6 ab c6 fe c6 05 7c 34 67 04 01 48 c7 c7 68 f8 6d 86 31 c0 e8 81 2e 9d fe <0f> 0b e9 22 ff ff ff e8 05 fa b5 fe 48 c7 c7 3e f8 f6 86 e8 a9 ab RSP: 0018:ffffc90001633c60 EFLAGS: 00010246 RAX: 15d08b2e34b77800 RBX: 0000000000000003 RCX: ffff88804c056c80 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000003 R08: ffffffff813767aa R09: 0001ffffffffffff R10: 0001ffffffffffff R11: ffff88804c056c80 R12: ffff888040b7d000 R13: ffff88804c206938 R14: ffff88804c206900 R15: ffff888041b18488 FS: 00000000022c9940(0000) GS:ffff88807ec00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9f9b122008 CR3: 0000000044b4b000 CR4: 0000000000750ee0 PKRU: 55555554 Call Trace: __refcount_sub_and_test -origin/./include/linux/refcount.h:283 [inline] __refcount_dec_and_test -origin/./include/linux/refcount.h:315 [inline] refcount_dec_and_test -origin/./include/linux/refcount.h:333 [inline] kref_put -origin/./include/linux/kref.h:64 [inline] kobject_put+0x17b/0x180 -origin/lib/kobject.c:753 cdev_del+0x4b/0x50 -origin/fs/char_dev.c:597 tty_unregister_device+0x99/0xd0 -origin/drivers/tty/tty_io.c:3343 gsmld_detach_gsm -origin/drivers/tty/n_gsm.c:2409 [inline] gsmld_close+0x6c/0x140 -origin/drivers/tty/n_gsm.c:2478 tty_ldisc_close -origin/drivers/tty/tty_ldisc.c:488 [inline] tty_ldisc_kill -origin/drivers/tty/tty_ldisc.c:636 [inline] tty_ldisc_release+0x1b6/0x400 -origin/drivers/tty/tty_ldisc.c:809 tty_release_struct+0x19/0xb0 -origin/drivers/tty/tty_io.c:1714 tty_release+0x9ad/0xa00 -origin/drivers/tty/tty_io.c:1885 __fput+0x260/0x4e0 -origin/fs/file_table.c:280 ____fput+0x11/0x20 -origin/fs/file_table.c:313 task_work_run+0x8e/0x110 -origin/kernel/task_work.c:140 tracehook_notify_resume -origin/./include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop -origin/kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x16b/0x1a0 -origin/kernel/entry/common.c:208 __syscall_exit_to_user_mode_work -origin/kernel/entry/common.c:290 [inline] syscall_exit_to_user_mode+0x20/0x40 -origin/kernel/entry/common.c:301 do_syscall_64+0x45/0x80 -origin/arch/x86/entry/common.c:56 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x419f1b Code: 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3 48 83 ec 18 89 7c 24 0c e8 63 fc ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2f 44 89 c7 89 44 24 0c e8 a1 fc ff ff 8b 44 RSP: 002b:00007fffd6e9a4f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000419f1b RDX: 0000001b31520000 RSI: 00000000089df867 RDI: 0000000000000003 RBP: 0000000000000004 R08: 0000000000000000 R09: 00000000005a0108 R10: 00007fffd6e9a620 R11: 0000000000000293 R12: 00000000005280c0 R13: 00000000005a01a0 R14: 00000000005a01a8 R15: 0000000000003cc6 Hao Sun 于2021年4月4日周日 下午4:45写道： > > Hi: > > When using Healer(https://github.com/SunHao-0/healer/tree/dev) to fuzz > the Linux kernel, I found a use-after-free vulnerability in cdev_del. > I found that Syzkaller had reported this bug a long time ago, but the > problem still exists. > Now I have collected the KASAN report and a reproduction program, I > hope this information can help you locate and solve the problem. > > Here is the detailed information: > commit: 5e46d1b78a03d52306f21f77a4e4a144b6d31486 > version: Linux 5.12-rc5 > git tree: upstream > kernel config and reproducing program can be found in the attachment. > KASAN report: > ================================================================== > BUG: KASAN: use-after-free in cdev_del+0x8b/0x90 -origin/fs/char_dev.c:596 > Read of size 4 at addr ffff888011e20864 by task executor/8066 > CPU: 1 PID: 8066 Comm: executor Not tainted 5.12.0-rc5+ #7 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > 1.13.0-1ubuntu1.1 04/01/2014 > Call Trace: > __dump_stack -origin/lib/dump_stack.c:79 [inline] > dump_stack+0xfa/0x151 -origin/lib/dump_stack.c:120 > print_address_description.constprop.0.cold+0x82/0x32c > -origin/mm/kasan/report.c:232 > __kasan_report -origin/mm/kasan/report.c:399 [inline] > kasan_report.cold+0x7c/0xd8 -origin/mm/kasan/report.c:416 > cdev_del+0x8b/0x90 -origin/fs/char_dev.c:596 > tty_unregister_device -origin/drivers/tty/tty_io.c:3343 [inline] > tty_unregister_device+0x112/0x1b0 -origin/drivers/tty/tty_io.c:3338 > gsmld_detach_gsm -origin/drivers/tty/n_gsm.c:2409 [inline] > gsmld_close+0xb3/0x1f0 -origin/drivers/tty/n_gsm.c:2478 > tty_ldisc_close.isra.0+0x110/0x190 -origin/drivers/tty/tty_ldisc.c:488 > tty_ldisc_kill+0x94/0x150 -origin/drivers/tty/tty_ldisc.c:636 > tty_ldisc_hangup+0x2d0/0x630 -origin/drivers/tty/tty_ldisc.c:756 > __tty_hangup.part.0+0x2f0/0x700 -origin/drivers/tty/tty_io.c:639 > __tty_hangup -origin/drivers/tty/tty_io.c:595 [inline] > tty_vhangup -origin/drivers/tty/tty_io.c:712 [inline] > tty_ioctl+0x992/0x14f0 -origin/drivers/tty/tty_io.c:2742 > vfs_ioctl -origin/fs/ioctl.c:48 [inline] > __do_sys_ioctl -origin/fs/ioctl.c:753 [inline] > __se_sys_ioctl -origin/fs/ioctl.c:739 [inline] > __x64_sys_ioctl+0x193/0x200 -origin/fs/ioctl.c:739 > do_syscall_64+0x2d/0x70 -origin/arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xae > RIP: 0033:0x47338d > Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 > 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d > 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007ff4d8de3c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 000000000059c128 RCX: 000000000047338d > RDX: 0000000000000000 RSI: 0000000000005437 RDI: 0000000000000003 > RBP: 00000000004e8e5d R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000059c128 > R13: 00007fff86f0a5ef R14: 00007fff86f0a790 R15: 00007ff4d8de3dc0