Re: [syzbot] [kernel?] KASAN: global-out-of-bounds Read in uevent_store

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    f1b8fa82cab7 Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=12e82379580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d1128bc53f2ef7f3
dashboard link: https://syzkaller.appspot.com/bug?extid=d164947c037324221043
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12597d79580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16e82379580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/932d85a2bda2/disk-f1b8fa82.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b6b8fb76e8d/vmlinux-f1b8fa82.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c246b61ee396/Image-f1b8fa82.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d164947c037324221043@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: global-out-of-bounds in kobject_action_type lib/kobject_uevent.c:86 [inline]
BUG: KASAN: global-out-of-bounds in kobject_synth_uevent+0x1e0/0x730 lib/kobject_uevent.c:200
Read of size 1 at addr ffff800087b429cb by task syz.0.17/4919

CPU: 1 UID: 0 PID: 4919 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
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
 __asan_report_load1_noabort+0x20/0x2c mm/kasan/report_generic.c:378
 kobject_action_type lib/kobject_uevent.c:86 [inline]
 kobject_synth_uevent+0x1e0/0x730 lib/kobject_uevent.c:200
 uevent_store+0x54/0x84 drivers/base/core.c:2851
 drv_attr_store+0x80/0xa4 drivers/base/bus.c:125
 sysfs_kf_write+0xe0/0x108 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x260/0x3b8 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x51c/0xa0c fs/read_write.c:687
 ksys_write+0x12c/0x228 fs/read_write.c:739
 __do_sys_write fs/read_write.c:750 [inline]
 __se_sys_write fs/read_write.c:747 [inline]
 __arm64_sys_write+0x84/0x98 fs/read_write.c:747
 __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:758
 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:777
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:590

The buggy address belongs to the variable:
 .str.34+0x6b/0x80

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:0x21a142
flags: 0x5ffc00000002000(reserved|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000002000 fffffdffc7685088 fffffdffc7685088 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff800087b42880: 07 f9 f9 f9 05 f9 f9 f9 07 f9 f9 f9 00 f9 f9 f9
 ffff800087b42900: 05 f9 f9 f9 07 f9 f9 f9 00 02 f9 f9 00 00 00 00
>ffff800087b42980: 00 00 00 00 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00
                                              ^
 ffff800087b42a00: 00 00 01 f9 f9 f9 f9 f9 00 00 00 04 f9 f9 f9 f9
 ffff800087b42a80: 00 00 02 f9 f9 f9 f9 f9 06 f9 f9 f9 00 00 00 00
==================================================================


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