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KASAN: slab-out-of-bounds Write in decode_data

Status: fixed on 2021/09/22 10:07
Reported-by: syzbot+85108ecaedb786fb81f4@syzkaller.appspotmail.com
Fix commit: 4e370cc081a7 net: 6pack: fix slab-out-of-bounds in decode_data
First crash: 1968d, last: 1421d
Fix bisection: fixed by (bisect log) :
commit 4e370cc081a78ee23528311ca58fd98a06768ec7
Author: Pavel Skripkin <paskripkin@gmail.com>
Date: Fri Aug 13 15:14:33 2021 +0000

  net: 6pack: fix slab-out-of-bounds in decode_data

  
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Write in decode_data hams 23 C done error 7 1893d 2048d 20/29 fixed on 2021/11/10 00:50
linux-4.14 KASAN: slab-out-of-bounds Write in decode_data 23 C inconclusive 2 1879d 1969d 0/1 upstream: reported C repro on 2020/02/22 08:09
▶ ▼ Fix bisection attempts (20)
Created Duration User Patch Repo Result
2021/09/21 20:10 3h56m bisect fix linux-4.19.y OK (1) job log
2021/08/22 16:45 28m bisect fix linux-4.19.y OK (0) job log log
2021/07/23 16:14 31m bisect fix linux-4.19.y OK (0) job log log
2021/06/23 15:50 23m bisect fix linux-4.19.y OK (0) job log log
2021/05/24 15:17 33m bisect fix linux-4.19.y OK (0) job log log
2021/04/24 14:00 33m bisect fix linux-4.19.y OK (0) job log log
2021/03/25 06:41 22m bisect fix linux-4.19.y OK (0) job log log
2021/02/23 05:58 23m bisect fix linux-4.19.y OK (0) job log log
2021/02/19 02:57 19m bisect fix linux-4.19.y error job log
2021/01/18 14:57 23m bisect fix linux-4.19.y OK (0) job log log
2020/12/19 10:53 24m bisect fix linux-4.19.y OK (0) job log log
2020/11/19 10:29 23m bisect fix linux-4.19.y OK (0) job log log
2020/10/20 10:03 25m bisect fix linux-4.19.y OK (0) job log log
2020/09/20 09:40 23m bisect fix linux-4.19.y OK (0) job log log
2020/08/21 09:12 27m bisect fix linux-4.19.y OK (0) job log log
2020/07/22 08:45 26m bisect fix linux-4.19.y OK (0) job log log
2020/06/22 08:21 24m bisect fix linux-4.19.y OK (0) job log log
2020/05/23 07:56 24m bisect fix linux-4.19.y OK (0) job log log
2020/04/23 07:20 25m bisect fix linux-4.19.y OK (0) job log log
2020/03/24 06:52 27m bisect fix linux-4.19.y OK (0) job log log

Sample crash report:
audit: type=1400 audit(1582440605.106:36): avc:  denied  { map } for  pid=8072 comm="syz-executor371" path="/root/syz-executor371299512" dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
sp0: Synchronizing with TNC
==================================================================
BUG: KASAN: slab-out-of-bounds in decode_data.part.0+0x23b/0x270 drivers/net/hamradio/6pack.c:863
Write of size 1 at addr ffff88808b30d94e by task kworker/u4:3/949

CPU: 0 PID: 949 Comm: kworker/u4:3 Not tainted 4.19.105-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
 __asan_report_store1_noabort+0x17/0x20 mm/kasan/report.c:435
 decode_data.part.0+0x23b/0x270 drivers/net/hamradio/6pack.c:863
 decode_data drivers/net/hamradio/6pack.c:985 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:988 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:458 [inline]
 sixpack_receive_buf+0xdfe/0x1440 drivers/net/hamradio/6pack.c:435
 tty_ldisc_receive_buf+0x15f/0x1c0 drivers/tty/tty_buffer.c:460
 tty_port_default_receive_buf+0x7d/0xb0 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:476 [inline]
 flush_to_ldisc+0x222/0x390 drivers/tty/tty_buffer.c:528
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 8072:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:531
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node+0x51/0x80 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:557 [inline]
 kvmalloc_node+0x68/0x100 mm/util.c:423
 kvmalloc include/linux/mm.h:577 [inline]
 kvzalloc include/linux/mm.h:585 [inline]
 alloc_netdev_mqs+0x98/0xdb0 net/core/dev.c:9122
 sixpack_open+0x104/0xbf5 drivers/net/hamradio/6pack.c:563
 tty_ldisc_open.isra.0+0x89/0xd0 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x2d7/0x690 drivers/tty/tty_ldisc.c:594
 tiocsetd drivers/tty/tty_io.c:2359 [inline]
 tty_ioctl+0x65e/0x1510 drivers/tty/tty_io.c:2603
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 6335:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcf/0x220 mm/slab.c:3822
 kfree_link+0x16/0x20 fs/libfs.c:1109
 do_delayed_call include/linux/delayed_call.h:28 [inline]
 put_link fs/namei.c:883 [inline]
 step_into fs/namei.c:1773 [inline]
 walk_component+0x447/0x2000 fs/namei.c:1830
 link_path_walk.part.0+0x594/0x1330 fs/namei.c:2139
 link_path_walk fs/namei.c:2073 [inline]
 path_openat+0x211/0x44a0 fs/namei.c:3536
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3fe/0x550 fs/open.c:1088
 __do_sys_open fs/open.c:1106 [inline]
 __se_sys_open fs/open.c:1101 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1101
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808b30c5c0
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 910 bytes to the right of
 4096-byte region [ffff88808b30c5c0, ffff88808b30d5c0)
The buggy address belongs to the page:
page:ffffea00022cc300 count:1 mapcount:0 mapping:ffff88812c31cdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea00022e6708 ffffea00022c0508 ffff88812c31cdc0
raw: 0000000000000000 ffff88808b30c5c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808b30d800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808b30d880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808b30d900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                                              ^
 ffff88808b30d980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808b30da00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/02/23 06:52 linux-4.19.y 4fccc2503536 2c36e7a7 .config console log report syz C ci2-linux-4-19
* Struck through repros no longer work on HEAD.