linux-kernel - Re: [syzbot] [bpf?] KASAN: invalid-access Write in do_bad

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Message-ID: <68e52a94.a00a0220.298cc0.047c.GAE@google.com>
Date: Tue, 07 Oct 2025 07:58:28 -0700
From: syzbot <syzbot+997752115a851cb0cf36@...kaller.appspotmail.com>
To: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org, 
	daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com, 
	john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org, 
	linux-kernel@...r.kernel.org, martin.lau@...ux.dev, sdf@...ichev.me, 
	song@...nel.org, syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] KASAN: invalid-access Write in do_bad_area

syzbot has found a reproducer for the following issue on:

HEAD commit:    c746c3b51698 Merge tag 'for-6.18-tag' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=149b5a7c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f49b7d923ce867a
dashboard link: https://syzkaller.appspot.com/bug?extid=997752115a851cb0cf36
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17ee792f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=163955cd980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/fa3fbcfdac58/non_bootable_disk-c746c3b5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/85796940f78d/vmlinux-c746c3b5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1d82d6550867/Image-c746c3b5.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+997752115a851cb0cf36@...kaller.appspotmail.com

==================================================================
BUG: KASAN: invalid-access in __memcpy+0xc/0x54 arch/arm64/lib/memcpy.S:250
Write at addr f0ff800083d6d268 by task syz.2.17/3596
Pointer tag: [f0], memory tag: [fe]

CPU: 1 UID: 0 PID: 3596 Comm: syz.2.17 Not tainted syzkaller #0 PREEMPT 
Hardware name: linux,dummy-virt (DT)
Call trace:
 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x78/0x90 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x108/0x61c mm/kasan/report.c:482
 kasan_report+0x88/0xac mm/kasan/report.c:595
 report_tag_fault arch/arm64/mm/fault.c:326 [inline]
 do_tag_recovery arch/arm64/mm/fault.c:338 [inline]
 __do_kernel_fault+0x170/0x1c8 arch/arm64/mm/fault.c:380
 do_bad_area+0x68/0x78 arch/arm64/mm/fault.c:480
 do_tag_check_fault+0x34/0x44 arch/arm64/mm/fault.c:853
 do_mem_abort+0x44/0x94 arch/arm64/mm/fault.c:929
 el1_abort+0x44/0x68 arch/arm64/kernel/entry-common.c:325
 el1h_64_sync_handler+0x50/0xac arch/arm64/kernel/entry-common.c:459
 el1h_64_sync+0x6c/0x70 arch/arm64/kernel/entry.S:591
 __memcpy+0xc/0x54 arch/arm64/lib/memcpy.S:250 (P)
 do_misc_fixups+0x174/0x1aac kernel/bpf/verifier.c:22553
 bpf_check+0x1348/0x2a24 kernel/bpf/verifier.c:24686
 bpf_prog_load+0x63c/0xcd4 kernel/bpf/syscall.c:3062
 __sys_bpf+0x2e0/0x1a88 kernel/bpf/syscall.c:6134
 __do_sys_bpf kernel/bpf/syscall.c:6244 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6242 [inline]
 __arm64_sys_bpf+0x24/0x34 kernel/bpf/syscall.c:6242
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
 el0_svc+0x34/0x10c arch/arm64/kernel/entry-common.c:744
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:763
 el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:596

The buggy address belongs to a 1-page vmalloc region starting at 0xf0ff800083d6d000 allocated at bpf_check+0x8c/0x2a24 kernel/bpf/verifier.c:24529
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x544b2
flags: 0x1fffc0000000000(node=0|zone=0|lastcpupid=0x7ff|kasantag=0xf)
raw: 01fffc0000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff800083d6d000: f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0
 ffff800083d6d100: f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 f0 fe fe fe fe
>ffff800083d6d200: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
                                     ^
 ffff800083d6d300: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff800083d6d400: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.