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Message-ID: <6982985a.a00a0220.37c87e.0018.GAE@google.com> Date: Tue, 03 Feb 2026 16:52:42 -0800 From: syzbot <syzbot+5a0f1995634f7c1dadbf@...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, netdev@...r.kernel.org, sdf@...ichev.me, song@...nel.org, syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev Subject: [syzbot] [bpf?] WARNING: refcount bug in __add_used_btf Hello, syzbot found the following issue on: HEAD commit: 6b95cc562de2 ftrace: Fix direct_functions leak in update_f.. git tree: bpf-next console output: https://syzkaller.appspot.com/x/log.txt?x=11a5fbfa580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b5a1ee0109784fc2 dashboard link: https://syzkaller.appspot.com/bug?extid=5a0f1995634f7c1dadbf compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1035fc5a580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12a1625a580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/e902619c9a45/disk-6b95cc56.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c8a15c0caf9a/vmlinux-6b95cc56.xz kernel image: https://storage.googleapis.com/syzbot-assets/3e7c64a9dbaf/bzImage-6b95cc56.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+5a0f1995634f7c1dadbf@...kaller.appspotmail.com ------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: syz.1.44/6186 Modules linked in: CPU: 0 UID: 0 PID: 6186 Comm: syz.1.44 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25 Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 2b 5b 23 fd 48 8d 3d 04 7d 58 0b 67 48 0f b9 3a eb 4a e8 18 5b 23 fd 48 8d 3d 01 7d 58 0b <67> 48 0f b9 3a eb 37 e8 05 5b 23 fd 48 8d 3d fe 7c 58 0b 67 48 0f RSP: 0018:ffffc90003337380 EFLAGS: 00010293 RAX: ffffffff84a11b58 RBX: 0000000000000002 RCX: ffff88802f648000 RDX: 0000000000000000 RSI: ffffffff8ece7f00 RDI: ffffffff8ff99860 RBP: 0000000000000000 R08: ffff88802f648000 R09: 0000000000000005 R10: 0000000000000004 R11: 0000000000000000 R12: ffff8880762d8854 R13: 1ffff9200078f60c R14: ffff888079bc6258 R15: ffff888079bc6200 FS: 00007fb9d62266c0(0000) GS:ffff8881256f8000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb9d53e8600 CR3: 00000000329a6000 CR4: 00000000003526f0 Call Trace: <TASK> __add_used_btf+0x152/0x2e0 kernel/bpf/verifier.c:21107 check_pseudo_btf_id+0x764/0xbb0 kernel/bpf/verifier.c:21238 resolve_pseudo_ldimm64+0x3f4/0xc90 kernel/bpf/verifier.c:21489 bpf_check+0x1d82/0x1ce00 kernel/bpf/verifier.c:25715 bpf_prog_load+0x1484/0x1ae0 kernel/bpf/syscall.c:3081 __sys_bpf+0x618/0x950 kernel/bpf/syscall.c:6218 __do_sys_bpf kernel/bpf/syscall.c:6331 [inline] __se_sys_bpf kernel/bpf/syscall.c:6329 [inline] __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6329 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb9d539aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fb9d6226028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 00007fb9d5615fa0 RCX: 00007fb9d539aeb9 RDX: 0000000000000094 RSI: 0000200000000180 RDI: 0000000000000005 RBP: 00007fb9d5408c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fb9d5616038 R14: 00007fb9d5615fa0 R15: 00007ffda6487988 </TASK> ---------------- Code disassembly (best guess): 0: eb 66 jmp 0x68 2: 85 db test %ebx,%ebx 4: 74 3e je 0x44 6: 83 fb 01 cmp $0x1,%ebx 9: 75 4c jne 0x57 b: e8 2b 5b 23 fd call 0xfd235b3b 10: 48 8d 3d 04 7d 58 0b lea 0xb587d04(%rip),%rdi # 0xb587d1b 17: 67 48 0f b9 3a ud1 (%edx),%rdi 1c: eb 4a jmp 0x68 1e: e8 18 5b 23 fd call 0xfd235b3b 23: 48 8d 3d 01 7d 58 0b lea 0xb587d01(%rip),%rdi # 0xb587d2b * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: eb 37 jmp 0x68 31: e8 05 5b 23 fd call 0xfd235b3b 36: 48 8d 3d fe 7c 58 0b lea 0xb587cfe(%rip),%rdi # 0xb587d3b 3d: 67 addr32 3e: 48 rex.W 3f: 0f .byte 0xf --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@...glegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title 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. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
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