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KASAN: global-out-of-bounds Read in soft_cursor (3)

Status: moderation: reported on 2026/06/19 17:21
Subsystems: fbdev
[Documentation on labels]
Reported-by: syzbot+9c989f8369c542e1a38f@syzkaller.appspotmail.com
First crash: 8d04h, last: 8d04h
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision Error
0bdf31f6-8daa-4200-b200-225379c6fef6 assessment-security 💥 KASAN: global-out-of-bounds Read in soft_cursor (3) 2026/06/21 00:03 2026/06/21 00:03 2026/06/21 00:03 43bfcdb07c3552e4664e1029672054ac0924d543 
failed to run ["git" "-c" "core.hooksPath=/dev/null" "fetch" "--force" "--tags" "433dfd5a8a5d80bbf0669b14e9ed908911a52dd6" "c2a9495bd873ccc028a308943bffcaac59e5f454"]: exit status 128
error: insuffici...
truncated to first 200 bytes; open job for full error
c5eb2494-c689-4c49-8c33-45f5a0108515 assessment-security 💥 KASAN: global-out-of-bounds Read in soft_cursor (3) 2026/06/18 08:47 2026/06/18 08:47 2026/06/18 08:47 b62b3ded1759f79b37600c5ffe2b0a81b919b0b0 
failed to run ["git" "-c" "core.hooksPath=/dev/null" "fetch" "--force" "--tags" "433dfd5a8a5d80bbf0669b14e9ed908911a52dd6" "c2a9495bd873ccc028a308943bffcaac59e5f454"]: exit status 128
error: insuffici...
truncated to first 200 bytes; open job for full error
be8f3004-f95b-492a-a8a9-c848a44bd97a assessment-security 💥 KASAN: global-out-of-bounds Read in soft_cursor (3) 2026/06/17 00:03 2026/06/17 00:03 2026/06/17 00:03 0e4b3e40a4572a10f991eaf3b70977db43e1fa9b 
failed to run ["git" "-c" "core.hooksPath=/dev/null" "fetch" "--force" "--tags" "433dfd5a8a5d80bbf0669b14e9ed908911a52dd6" "c2a9495bd873ccc028a308943bffcaac59e5f454"]: exit status 128
error: insuffici...
truncated to first 200 bytes; open job for full error
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in soft_cursor (2) fbdev 17 9 140d 274d 0/29 auto-obsoleted due to no activity on 2026/05/14 02:42
upstream KASAN: global-out-of-bounds Read in soft_cursor (2) fbdev 17 1 486d 482d 0/29 auto-obsoleted due to no activity on 2025/05/23 01:13
linux-4.19 KASAN: global-out-of-bounds Read in soft_cursor 17 C done 22 1855d 2323d 1/1 fixed on 2021/06/24 08:01
upstream KASAN: global-out-of-bounds Read in soft_cursor fbdev 17 11 2159d 2385d 0/29 auto-closed as invalid on 2020/11/22 03:01
linux-4.14 KASAN: global-out-of-bounds Read in soft_cursor 17 C error 19 1382d 2381d 0/1 upstream: reported C repro on 2019/12/16 00:09
linux-5.15 KASAN: null-ptr-deref Read in soft_cursor origin:lts-only 11 syz error 1 1122d 1122d 0/3 auto-obsoleted due to no activity on 2024/12/24 15:39
linux-4.14 KASAN: use-after-free Read in soft_cursor 19 C inconclusive 7 1882d 2393d 0/1 upstream: reported C repro on 2019/12/04 13:11
linux-4.19 KASAN: slab-out-of-bounds Read in soft_cursor (2) 17 C done 8 1858d 1980d 1/1 fixed on 2021/06/23 17:43
upstream general protection fault in soft_cursor fbdev 11 C 3 1123d 1123d 22/29 fixed on 2023/07/01 16:05
linux-4.14 KASAN: slab-out-of-bounds Read in soft_cursor 17 C unreliable 57 1863d 2394d 0/1 upstream: reported C repro on 2019/12/03 14:54

Sample crash report:
==================================================================
BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
Read of size 16 at addr ffff800086c57970 by task syz.7.609/8216

CPU: 0 UID: 0 PID: 8216 Comm: syz.7.609 Tainted: G             L      syzkaller #0 PREEMPT 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 print_address_description+0xb0/0x238 mm/kasan/report.c:378
 print_report+0x68/0x84 mm/kasan/report.c:482
 kasan_report+0x8c/0xc4 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x17c/0x1ac mm/kasan/generic.c:200
 __asan_memcpy+0x3c/0x84 mm/kasan/shadow.c:105
 soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
 bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365
 fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427
 hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883
 update_region+0x100/0x18c drivers/tty/vt/vt.c:669
 vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685
 do_loop_readv_writev+0x24c/0x3dc fs/read_write.c:-1
 vfs_writev+0x2c8/0x630 fs/read_write.c:1061
 do_writev+0x134/0x2a8 fs/read_write.c:1105
 __do_sys_writev fs/read_write.c:1173 [inline]
 __se_sys_writev fs/read_write.c:1170 [inline]
 __arm64_sys_writev+0x80/0x94 fs/read_write.c:1170
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49
 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121
 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140
 el0_svc+0x64/0x260 arch/arm64/kernel/entry-common.c:736
 el0t_64_sync_handler+0x48/0x148 arch/arm64/kernel/entry-common.c:755
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:594

The buggy address belongs to the variable:
 fontdata_8x16+0x1010/0x1480

The buggy address belongs to a vmalloc virtual mapping
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x219857
flags: 0x5ffc00000002000(reserved|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000002000 fffffdffc76615c8 fffffdffc76615c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff800086c57800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff800086c57880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff800086c57900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9
                                                             ^
 ffff800086c57980: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
 ffff800086c57a00: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/15 17:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c2a9495bd873 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 KASAN: global-out-of-bounds Read in soft_cursor
* Struck through repros no longer work on HEAD.