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Thu, 12 Nov 2026 22:10:48 -0800 (PST) Date: Thu, 12 Nov 2026 22:10:48 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af6a9e8.fe96acdb.12252b.0000.GAE@google.com> Subject: [syzbot] [kernfs?] BUG: unable to handle kernel paging request in kernfs_unlink_sibling From: syzbot To: driver-core@lists.linux.dev, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tj@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 58c1eb84e977 arm64: sdei: Preserve the interrupted context.. 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=10ee7f8d580000 kernel config: https://syzkaller.appspot.com/x/.config?x=a58b6b4d667e7a61 dashboard link: https://syzkaller.appspot.com/bug?extid=02ab1258b7fa66eb1f7f compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 userspace arch: arm64 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17119f8d580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b1ec47537e12/disk-58c1eb84.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/3bca0c2b1169/vmlinux-58c1eb84.xz kernel image: https://storage.googleapis.com/syzbot-assets/0a7c49594d5a/Image-58c1eb84.gz.xz AI-generated root cause summary: The crash manifests during network namespace teardown (cleanup_net -> rdma_dev_exit_net -> ib_free_port_attrs -> destroy_gid_attrs -> kernfs_unlink_sibling -> rb_erase) when ____rb_erase_color encounters a NULL sibling pointer and dereferences address 0x0 (detected by KASAN at shadow address dfff800000000000). In a valid red-black tree, ____rb_erase_color is only entered after deleting a black node, so the sibling subtree must contain at least one black node and sibling can never be NULL; furthermore, all kernfs directory operations are strictly protected by root->kernfs_rwsem. This rbtree corruption is induced externally: userspace mmaps the PCI BAR0 MMIO window exposed via sysfs (/sys/bus/pci/devices/.../resource0 in drivers/pci/pci-sysfs.c) and writes arbitrary data into device MMIO space, reprogramming hardware DMA queues and causing device DMA to overwrite kernel memory structures. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=02ab1258b7fa66eb1f7f IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+02ab1258b7fa66eb1f7f@syzkaller.appspotmail.com Unable to handle kernel paging request at virtual address dfff800000000000 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0 [dfff800000000000] address between user and kernel address ranges Internal error: Oops: 0000000096000005 [#1] SMP Modules linked in: CPU: 1 UID: 0 PID: 1195 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 Workqueue: netns cleanup_net pstate: 63400005 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : ____rb_erase_color lib/rbtree.c:354 [inline] pc : rb_erase+0x4e4/0xba0 lib/rbtree.c:445 lr : kernfs_unlink_sibling+0x190/0x218 fs/kernfs/dir.c:449 sp : ffff800094d775f0 x29: ffff800094d77600 x28: ffff0000d985c408 x27: ffff0000d985c410 x26: 1fffe0001b30b882 x25: dfff800000000000 x24: ffff0000c6b58ca0 x23: 0000000000000000 x22: 0000000000000000 x21: ffff0000d98545e0 x20: ffff0000d985c400 x19: 0000000000000000 x18: 1fffe000359d3e28 x17: 0000000000000003 x16: ffff8000898b7000 x15: 0000000000000000 x14: 0000000000287419 x13: 0000000000000001 x12: 0000000000000003 x11: 0000000000000000 x10: 0000000000000001 x9 : 0000000000000000 x8 : 0000000000000000 x7 : ffff800080f6a0dc x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff80008046e414 x2 : 0000000000000001 x1 : ffff0000c6b58ca0 x0 : ffff0000d98545e0 Call trace: ____rb_erase_color lib/rbtree.c:354 [inline] (P) rb_erase+0x4e4/0xba0 lib/rbtree.c:445 (P) kernfs_unlink_sibling+0x190/0x218 fs/kernfs/dir.c:449 __kernfs_remove+0x36c/0x748 fs/kernfs/dir.c:1584 kernfs_remove_by_name_ns+0x70/0xd0 fs/kernfs/dir.c:1796 kernfs_remove_by_name include/linux/kernfs.h:644 [inline] remove_files+0x90/0x184 fs/sysfs/group.c:28 sysfs_remove_group+0x98/0x160 fs/sysfs/group.c:328 sysfs_remove_groups+0x5c/0xb4 fs/sysfs/group.c:352 destroy_gid_attrs drivers/infiniband/core/sysfs.c:1143 [inline] ib_free_port_attrs+0xa8/0x340 drivers/infiniband/core/sysfs.c:1367 remove_one_compat_dev+0x54/0x7c drivers/infiniband/core/device.c:1035 rdma_dev_exit_net+0x188/0x388 drivers/infiniband/core/device.c:1173 ops_exit_list net/core/net_namespace.c:200 [inline] ops_undo_list+0x3cc/0x81c net/core/net_namespace.c:253 cleanup_net+0x474/0x6c4 net/core/net_namespace.c:708 process_one_work kernel/workqueue.c:3495 [inline] process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3578 worker_thread+0x798/0xbd0 kernel/workqueue.c:3659 kthread+0x304/0x3d4 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 Code: 91004280 968b3531 f9400376 d343fed7 (38796ae8) ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess): 0: 91004280 add x0, x20, #0x10 4: 968b3531 bl 0xfffffffffa2cd4c8 8: f9400376 ldr x22, [x27] c: d343fed7 lsr x23, x22, #3 * 10: 38796ae8 ldrb w8, [x23, x25] <-- trapping instruction --- 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 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