KASAN: global-out-of-bounds Read in bit_putcs (2)

Status: auto-closed as invalid on 2021/02/09 16:38
Subsystems: fbdev
[Documentation on labels]
Reported-by: syzbot+a889d70ef11d6e0f6f22@syzkaller.appspotmail.com
First crash: 2135d, last: 2118d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KASAN: global-out-of-bounds Read in bit_putcs (2) 1 (2) 2020/09/26 15:55
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: global-out-of-bounds Read in bit_putcs 19 syz, C error 241 1418d 2428d 0/1 upstream: reported C repro on 2019/12/07 16:26
linux-6.1 KASAN: global-out-of-bounds Read in bit_putcs 17 1 627d 627d 0/3 auto-obsoleted due to no activity on 2025/02/19 05:01
upstream KASAN: global-out-of-bounds Read in bit_putcs fbdev 17 syz, C done 262 2137d 2430d 15/29 fixed on 2020/09/25 01:17
linux-4.19 KASAN: global-out-of-bounds Read in bit_putcs 19 syz, C done 214 1894d 2431d 1/1 fixed on 2021/06/24 08:01
upstream KASAN: global-out-of-bounds Read in bit_putcs (3) fbdev 17 syz, C 58 278d 730d 29/29 fixed on 2026/01/07 12:29

Sample crash report:
==================================================================
BUG: KASAN: global-out-of-bounds in __fb_pad_aligned_buffer include/linux/fb.h:654 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
BUG: KASAN: global-out-of-bounds in bit_putcs+0xbb6/0xd20 drivers/video/fbdev/core/bitblit.c:185
Read of size 1 at addr ffffffff8a7bbd00 by task syz-executor.2/26546

CPU: 0 PID: 26546 Comm: syz-executor.2 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 __fb_pad_aligned_buffer include/linux/fb.h:654 [inline]
 bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
 bit_putcs+0xbb6/0xd20 drivers/video/fbdev/core/bitblit.c:185
 fbcon_putcs+0x35a/0x450 drivers/video/fbdev/core/fbcon.c:1308
 con_flush drivers/tty/vt/vt.c:2575 [inline]
 do_con_write+0xb6b/0x1dd0 drivers/tty/vt/vt.c:2905
 con_write+0x22/0xb0 drivers/tty/vt/vt.c:3250
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0x3ce/0xf80 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x4d9/0x870 drivers/tty/tty_io.c:1046
 vfs_write+0x2b0/0x730 fs/read_write.c:584
 ksys_write+0x12d/0x250 fs/read_write.c:639
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45de59
Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8d8fde5c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000003a600 RCX: 000000000045de59
RDX: 0000000000001006 RSI: 0000000020001440 RDI: 0000000000000004
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffffe8f7d2f R14: 00007f8d8fde69c0 R15: 000000000118bf2c

The buggy address belongs to the variable:
 fontdata_8x16+0x1180/0x1aa0

Memory state around the buggy address:
 ffffffff8a7bbc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8a7bbc80: 00 00 00 00 00 00 00 00 f9 f9 f9 f9 00 00 00 00
>ffffffff8a7bbd00: f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9 00 00 00 00
                   ^
 ffffffff8a7bbd80: f9 f9 f9 f9 00 00 00 02 f9 f9 f9 f9 00 00 00 f9
 ffffffff8a7bbe00: f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9 00 00 00 00
==================================================================

Crashes (13):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/10/12 16:37 upstream bbf5c979011a d32b0bbf .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/11 23:27 upstream 3dd0130f2430 4a77ae0b .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/11 03:44 upstream da690031a5d6 4a77ae0b .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/11 00:42 upstream 6f2f486d57c4 4a77ae0b .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/11 00:00 upstream 6f2f486d57c4 4a77ae0b .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/10 17:56 upstream 6f2f486d57c4 4a77ae0b .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/07 04:07 upstream c85fb28b6f99 1880b4a9 .config console log report info ci-upstream-kasan-gce-root
2020/10/07 03:23 upstream c85fb28b6f99 1880b4a9 .config console log report info ci-upstream-kasan-gce-root
2020/10/04 01:47 upstream 22fbc037cd32 1a3f9408 .config console log report info ci-upstream-kasan-gce-selinux-root
2020/10/02 22:56 upstream 472e5b056f00 4969d6ca .config console log report info ci-upstream-kasan-gce-root
2020/09/30 02:55 upstream ccc1d052eff9 5abc3f1a .config console log report info ci-upstream-kasan-gce-root
2020/09/28 04:58 upstream a1bffa48745a 5dd8aee8 .config console log report info ci-upstream-kasan-gce-root
2020/09/26 01:27 upstream 171d4ff79f96 4a006f63 .config console log report info ci-upstream-kasan-gce-root
* Struck through repros no longer work on HEAD.