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KASAN: global-out-of-bounds Read in fbcon_resize

Status: fixed on 2020/11/21 10:42
Reported-by: syzbot+a474d8001418c423ce38@syzkaller.appspotmail.com
Fix commit: d31eccab7abd fbcon: Fix user font detection test at fbcon_resize().
First crash: 1540d, last: 1492d
Fix bisection: fixed by (bisect log) :
commit d31eccab7abd41e9d198c0f4f226d937cc7bbd58
Author: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Thu Sep 10 22:57:06 2020 +0000

  fbcon: Fix user font detection test at fbcon_resize().

  
▶ ▼ Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: global-out-of-bounds Read in fbcon_resize fbdev C error 673 1522d 1554d 15/28 fixed on 2020/10/10 01:52
linux-4.19 KASAN: global-out-of-bounds Read in fbcon_resize C done 286 1520d 1540d 1/1 fixed on 2020/10/23 18:53

Sample crash report:
audit: type=1400 audit(1599198211.325:8): avc:  denied  { execmem } for  pid=6364 comm="syz-executor689" scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=process permissive=1
==================================================================
BUG: KASAN: global-out-of-bounds in fbcon_resize+0x705/0x7b0 drivers/video/fbdev/core/fbcon.c:2145
Read of size 4 at addr ffffffff86e69218 by task syz-executor689/6364

CPU: 1 PID: 6364 Comm: syz-executor689 Not tainted 4.14.196-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+0x5/0x1d3 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_load4_noabort+0x68/0x70 mm/kasan/report.c:429
 fbcon_resize+0x705/0x7b0 drivers/video/fbdev/core/fbcon.c:2145
 resize_screen drivers/tty/vt/vt.c:839 [inline]
 vc_do_resize+0x38b/0xe00 drivers/tty/vt/vt.c:901
 vt_ioctl+0x76f/0x1f50 drivers/tty/vt/vt_ioctl.c:850
 tty_ioctl+0x50f/0x13c0 drivers/tty/tty_io.c:2661
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x4402a9
RSP: 002b:00007ffe6b515638 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402a9
RDX: 0000000020000000 RSI: 0000000000005609 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 000000000000000d R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b10
R13: 0000000000401ba0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the variable:
 font_vga_8x16+0x58/0x60

Memory state around the buggy address:
 ffffffff86e69100: 00 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa
 ffffffff86e69180: 00 fa fa fa fa fa fa fa 00 00 00 00 00 fa fa fa
>ffffffff86e69200: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
                            ^
 ffffffff86e69280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff86e69300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (529):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/09/04 05:45 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report syz C ci2-linux-4-14
2020/09/03 23:49 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report syz C ci2-linux-4-14
2020/09/04 08:46 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report syz ci2-linux-4-14
2020/09/03 21:12 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report syz ci2-linux-4-14
2020/10/21 09:34 linux-4.14.y cbfa1702aaf6 e761439e .config console log report info ci2-linux-4-14
2020/10/21 04:35 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/21 02:53 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/21 00:34 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 23:11 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 19:25 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 19:20 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 14:17 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 12:14 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 09:56 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 07:24 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 04:43 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/20 01:25 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/19 20:41 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/19 15:15 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/19 10:18 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/19 09:10 linux-4.14.y cbfa1702aaf6 ff4a3345 .config console log report info ci2-linux-4-14
2020/10/19 07:08 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/19 00:26 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/18 21:24 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/18 19:17 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/18 09:57 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/18 07:48 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/18 05:05 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 23:09 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 20:20 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 17:42 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 13:35 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 11:49 linux-4.14.y cbfa1702aaf6 fea47c01 .config console log report info ci2-linux-4-14
2020/10/17 02:37 linux-4.14.y cbfa1702aaf6 6e262c73 .config console log report info ci2-linux-4-14
2020/10/16 16:23 linux-4.14.y cbfa1702aaf6 6e262c73 .config console log report info ci2-linux-4-14
2020/10/16 14:37 linux-4.14.y cbfa1702aaf6 6e262c73 .config console log report info ci2-linux-4-14
2020/10/16 13:07 linux-4.14.y cbfa1702aaf6 6e262c73 .config console log report info ci2-linux-4-14
2020/10/15 20:55 linux-4.14.y cbfa1702aaf6 6e262c73 .config console log report info ci2-linux-4-14
2020/10/15 11:41 linux-4.14.y cbfa1702aaf6 63869021 .config console log report info ci2-linux-4-14
2020/10/15 08:47 linux-4.14.y cbfa1702aaf6 63869021 .config console log report info ci2-linux-4-14
2020/10/15 05:09 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/15 04:08 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/15 03:20 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/15 01:58 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/15 00:02 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/14 22:06 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/14 16:39 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/14 12:41 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/14 10:30 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/10/14 09:18 linux-4.14.y cbfa1702aaf6 fc7735a2 .config console log report info ci2-linux-4-14
2020/09/03 10:02 linux-4.14.y 2f166cdcf8a9 abf9ba4f .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.