KASAN: use-after-free Read in bit

KASAN: use-after-free Read in bit_putcs
Status: auto-closed as invalid on 2021/01/15 05:05
Reported-by: syzbot+1c95398cbebffb00dba3@syzkaller.appspotmail.com
First crash: 527d, last: 241d

similar bugs (4):
Kernel	Title	Repro	Count	Last	Reported	Patched	Status
linux-4.14	KASAN: global-out-of-bounds Read in bit_putcs	C	234	9h28m	525d	0/1	upstream: reported C repro on 2019/12/07 16:26
upstream	KASAN: use-after-free Read in bit_putcs	C	12	227d	447d	17/22	fixed on 2020/11/16 12:12
linux-4.19	KASAN: global-out-of-bounds Read in bit_putcs	C	212	1d01h	528d	0/1	upstream: reported C repro on 2019/12/04 22:22
linux-4.19	KASAN: use-after-free Read in bit_putcs		18	291d	525d	0/1	auto-closed as invalid on 2020/11/26 07:35

Sample crash report:

==================================================================
BUG: KASAN: use-after-free in __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
BUG: KASAN: use-after-free in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
BUG: KASAN: use-after-free in bit_putcs+0xab7/0xc30 drivers/video/fbdev/core/bitblit.c:185
Read of size 1 at addr ffff88805ff256be by task syz-executor.4/8958

CPU: 1 PID: 8958 Comm: syz-executor.4 Not tainted 4.14.198-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load1_noabort+0x68/0x70 mm/kasan/report.c:427
 __fb_pad_aligned_buffer include/linux/fb.h:663 [inline]
 bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
 bit_putcs+0xab7/0xc30 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x2fe/0x480 drivers/video/fbdev/core/fbcon.c:1301
 con_flush drivers/tty/vt/vt.c:2206 [inline]
 do_con_write+0x9dd/0x19b0 drivers/tty/vt/vt.c:2453
 con_write+0x21/0xa0 drivers/tty/vt/vt.c:2805
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x352/0xda0 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:959 [inline]
 tty_write+0x410/0x740 drivers/tty/tty_io.c:1043
 __vfs_write+0xe4/0x630 fs/read_write.c:480
 vfs_write+0x17f/0x4d0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d5f9
RSP: 002b:00007ff660951c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000038980 RCX: 000000000045d5f9
RDX: 0000000000001006 RSI: 0000000020001440 RDI: 0000000000000005
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffe32b2d6ff R14: 00007ff6609529c0 R15: 000000000118cf4c

Allocated by task 8298:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 __do_kmalloc_node mm/slab.c:3682 [inline]
 __kmalloc_node_track_caller+0x4c/0x70 mm/slab.c:3696
 __kmalloc_reserve net/core/skbuff.c:137 [inline]
 __alloc_skb+0x96/0x510 net/core/skbuff.c:205
 alloc_skb_fclone include/linux/skbuff.h:1022 [inline]
 sk_stream_alloc_skb+0xb1/0x760 net/ipv4/tcp.c:855
 tcp_sendmsg_locked+0xed8/0x2ef0 net/ipv4/tcp.c:1301
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
 inet_sendmsg+0x11a/0x4e0 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0x100 net/socket.c:656
 sock_write_iter+0x22c/0x370 net/socket.c:925
 call_write_iter include/linux/fs.h:1778 [inline]
 new_sync_write fs/read_write.c:469 [inline]
 __vfs_write+0x44c/0x630 fs/read_write.c:482
 vfs_write+0x17f/0x4d0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 8298:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xc9/0x250 mm/slab.c:3815
 skb_free_head net/core/skbuff.c:554 [inline]
 skb_release_data+0x5f6/0x820 net/core/skbuff.c:574
 skb_release_all net/core/skbuff.c:631 [inline]
 __kfree_skb+0x46/0x60 net/core/skbuff.c:645
 sk_wmem_free_skb include/net/sock.h:1425 [inline]
 tcp_clean_rtx_queue net/ipv4/tcp_input.c:3186 [inline]
 tcp_ack+0x1872/0x43c0 net/ipv4/tcp_input.c:3686
 tcp_rcv_established+0xebb/0x17a0 net/ipv4/tcp_input.c:5499
 tcp_v4_do_rcv+0x541/0x7d0 net/ipv4/tcp_ipv4.c:1476
 sk_backlog_rcv include/net/sock.h:921 [inline]
 __release_sock+0x12a/0x350 net/core/sock.c:2269
 release_sock+0x54/0x1b0 net/core/sock.c:2805
 tcp_sendmsg+0x36/0x40 net/ipv4/tcp.c:1458
 inet_sendmsg+0x11a/0x4e0 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xb5/0x100 net/socket.c:656
 sock_write_iter+0x22c/0x370 net/socket.c:925
 call_write_iter include/linux/fs.h:1778 [inline]
 new_sync_write fs/read_write.c:469 [inline]
 __vfs_write+0x44c/0x630 fs/read_write.c:482
 vfs_write+0x17f/0x4d0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88805ff25640
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 126 bytes inside of
 2048-byte region [ffff88805ff25640, ffff88805ff25e40)
The buggy address belongs to the page:
page:ffffea00017fc900 count:1 mapcount:0 mapping:ffff88805ff24540 index:0xffff88805ff25640 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88805ff24540 ffff88805ff25640 0000000100000001
raw: ffffea000257c1a0 ffffea00023c16a0 ffff88812fe50c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88805ff25580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88805ff25600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88805ff25680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88805ff25700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805ff25780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (17):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info
ci2-linux-4-14	2020/09/17 05:04	linux-4.14.y	cbfa1702	8247808b	.config	log	report	info
ci2-linux-4-14	2020/08/30 02:22	linux-4.14.y	d7e78d08	d5a3ae1f	.config	log	report
ci2-linux-4-14	2020/08/25 14:57	linux-4.14.y	6a24ca25	344da168	.config	log	report
ci2-linux-4-14	2020/08/24 03:24	linux-4.14.y	6a24ca25	cef5ae68	.config	log	report
ci2-linux-4-14	2020/08/15 19:13	linux-4.14.y	14b58326	5ce13532	.config	log	report
ci2-linux-4-14	2020/07/04 12:59	linux-4.14.y	b850307b	4f739670	.config	log	report
ci2-linux-4-14	2020/06/24 15:58	linux-4.14.y	b850307b	41694dbf	.config	log	report
ci2-linux-4-14	2020/06/19 14:32	linux-4.14.y	b850307b	123cf502	.config	log	report
ci2-linux-4-14	2020/06/12 17:35	linux-4.14.y	b850307b	3036d6fd	.config	log	report
ci2-linux-4-14	2020/05/24 13:57	linux-4.14.y	a41ba30d	ce7ca010	.config	log	report
ci2-linux-4-14	2020/05/23 22:31	linux-4.14.y	a41ba30d	96c92ad3	.config	log	report
ci2-linux-4-14	2020/05/20 12:24	linux-4.14.y	a41ba30d	1255f02a	.config	log	report
ci2-linux-4-14	2020/04/30 11:24	linux-4.14.y	050272a0	3698959a	.config	log	report
ci2-linux-4-14	2020/04/12 08:12	linux-4.14.y	4520f06b	a8c6a3f8	.config	log	report
ci2-linux-4-14	2020/03/17 22:05	linux-4.14.y	12cd844a	97bc55ce	.config	log	report
ci2-linux-4-14	2019/12/28 17:37	linux-4.14.y	e1f7d50a	af6b8ef8	.config	log	report
ci2-linux-4-14	2019/12/06 08:48	linux-4.14.y	a844dc4c	98b4ef2d	.config	log	report