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Tue, 27 Oct 2026 05:08:55 -0700 (PDT) Date: Tue, 27 Oct 2026 05:08:55 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ae09457.f0fe5aea.79aa1.008c.GAE@google.com> Subject: [syzbot] [nvme?] kernel BUG in nvmet_fc_remove_port From: syzbot To: hch@lst.de, justin.tee@broadcom.com, kch@nvidia.com, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, nareshgottumukkala83@gmail.com, paul.ely@broadcom.com, sagi@grimberg.me, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 6b4b543fa187 Merge tag 'parisc-for-7.4-rc1' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16ce8f0d580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b4c032ed87e6e91c dashboard link: https://syzkaller.appspot.com/bug?extid=df0058a8d0bdce7c4059 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17db5e35580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1413f195580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-6b4b543f.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/003ef0d7eda6/vmlinux-6b4b543f.xz kernel image: https://storage.googleapis.com/syzbot-assets/022618083bf9/bzImage-6b4b543f.xz AI-generated root cause summary: In the NVMe target subsystem, port attribute store handlers in drivers/nvme/target/configfs.c (such as nvmet_addr_trtype_store) do not acquire nvmet_config_sem and only check port->enabled. Because port->enabled is not set to true until after ops->add_port() finishes in nvmet_enable_port(), a concurrent write to addr_trtype can race and switch port->disc_addr.trtype (e.g., from TCP to FC). When disabling the port, nvmet_disable_port() in drivers/nvme/target/core.c indexes nvmet_transports using port->disc_addr.trtype instead of using port->tr_ops, causing type confusion on port->priv (treating struct nvmet_tcp_port as struct nvmet_fc_port_entry) and resulting in memory corruption, refcount underflow, and use-after-free. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=df0058a8d0bdce7c4059 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+df0058a8d0bdce7c4059@syzkaller.appspotmail.com nvmet_tcp: enabling port 1 (127.0.0.1:4420) refcount_t: underflow; use-after-free. ------------[ cut here ]------------ kernel BUG at lib/refcount.c:37! Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 6113 Comm: syz.0.43 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:refcount_warn_saturate+0xd7/0x110 lib/refcount.c:37 Code: 67 48 0f b9 3a e8 b9 e8 d6 fc 5b 5d e9 c2 d6 b5 06 77 19 83 fd 02 74 3e e8 a6 e8 d6 fc 48 c7 c7 c0 08 81 8c e8 ba 43 eb fb 90 <0f> 0b e8 92 e8 d6 fc 48 8d 3d 6b 27 3d 0d 67 48 0f b9 3a e8 81 e8 RSP: 0018:ffffc900039d7c00 EFLAGS: 00010086 RAX: 0000000000000026 RBX: ffff8880549e4678 RCX: 0000000000000000 RDX: 0000000000000026 RSI: ffffffff81ebe399 RDI: fffff5200073af71 RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff9200073af85 R13: 0000000000000000 R14: 0000000000000000 R15: ffff8880549e4678 FS: 0000555566238500(0000) GS:ffff8880d449e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8d01471220 CR3: 000000002d14f000 CR4: 0000000000352ef0 Call Trace: __refcount_sub_and_test include/linux/refcount.h:400 [inline] __refcount_dec_and_test include/linux/refcount.h:432 [inline] refcount_dec_and_test include/linux/refcount.h:450 [inline] kref_put include/linux/kref.h:64 [inline] nvmet_fc_tgtport_put drivers/nvme/target/fc.c:1464 [inline] nvmet_fc_portentry_unbind drivers/nvme/target/fc.c:1278 [inline] nvmet_fc_remove_port+0x4c2/0x5f0 drivers/nvme/target/fc.c:2930 nvmet_disable_port+0x13c/0x200 drivers/nvme/target/core.c:400 nvmet_port_subsys_drop_link+0x26b/0x310 drivers/nvme/target/configfs.c:1189 configfs_unlink+0x3cc/0x800 fs/configfs/symlink.c:258 vfs_unlink+0x2f0/0xbd0 fs/namei.c:5661 filename_unlinkat+0x408/0x730 fs/namei.c:5731 __do_sys_unlinkat fs/namei.c:5760 [inline] __se_sys_unlinkat fs/namei.c:5752 [inline] __x64_sys_unlinkat+0xc0/0x130 fs/namei.c:5752 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f8d0159f559 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:00007ffef6d7e878 EFLAGS: 00000246 ORIG_RAX: 0000000000000107 RAX: ffffffffffffffda RBX: 00007f8d01825fa0 RCX: 00007f8d0159f559 RDX: 0000000000000000 RSI: 0000200000000780 RDI: ffffffffffffff9c RBP: 00007f8d01636b20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f8d01825fac R14: 00007f8d01825fa0 R15: 00007f8d01825fa0 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:refcount_warn_saturate+0xd7/0x110 lib/refcount.c:37 Code: 67 48 0f b9 3a e8 b9 e8 d6 fc 5b 5d e9 c2 d6 b5 06 77 19 83 fd 02 74 3e e8 a6 e8 d6 fc 48 c7 c7 c0 08 81 8c e8 ba 43 eb fb 90 <0f> 0b e8 92 e8 d6 fc 48 8d 3d 6b 27 3d 0d 67 48 0f b9 3a e8 81 e8 RSP: 0018:ffffc900039d7c00 EFLAGS: 00010086 RAX: 0000000000000026 RBX: ffff8880549e4678 RCX: 0000000000000000 RDX: 0000000000000026 RSI: ffffffff81ebe399 RDI: fffff5200073af71 RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff9200073af85 R13: 0000000000000000 R14: 0000000000000000 R15: ffff8880549e4678 FS: 0000555566238500(0000) GS:ffff8880d449e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f8d01471220 CR3: 000000002d14f000 CR4: 0000000000352ef0 --- 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@googlegroups.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