Hi, We found a bug in Linux 6.10. It is probably a null pointer reference bug. The reason is probably that before line 123 of fs/proc/proc_sysctl.c(entry = &head->ctl_table[ctl_node - head->node];), there is no null pointer check for `head`. The bug report is as follow: Bug report: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 PID: 8491 Comm: kworker/0:5 Not tainted 6.10.0 #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Workqueue: events free_ipc RIP: 0010:find_entry fs/proc/proc_sysctl.c:123 [inline] RIP: 0010:put_links+0x19e/0x4f0 fs/proc/proc_sysctl.c:1472 Code: 0f 84 33 02 00 00 49 8d 5f 18 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 bc 94 c6 ff 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 a3 94 c6 ff 48 8b 2b 48 89 5c 24 RSP: 0018:ffffc9000bf87980 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888026909e00 RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000 RBP: 000000000000000b R08: ffffffff822dc888 R09: ffffffff822dc93a R10: 0000000000000002 R11: ffff888026909e00 R12: ffffffff8d9d70d0 R13: dffffc0000000000 R14: ffffffff8ba0d080 R15: ffff888018108058 FS: 0000000000000000(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f4e64ba9930 CR3: 0000000020a88000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> drop_sysctl_table+0xed/0x4f0 fs/proc/proc_sysctl.c:1494 unregister_sysctl_table+0x3d/0x60 fs/proc/proc_sysctl.c:1520 retire_ipc_sysctls+0x5a/0x80 ipc/ipc_sysctl.c:310 free_ipc_ns ipc/namespace.c:158 [inline] free_ipc+0x139/0x280 ipc/namespace.c:179 process_one_work kernel/workqueue.c:3248 [inline] process_scheduled_works+0x977/0x1410 kernel/workqueue.c:3329 worker_thread+0xaa0/0x1020 kernel/workqueue.c:3409 kthread+0x2eb/0x380 kernel/kthread.c:389 ret_from_fork+0x49/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:find_entry fs/proc/proc_sysctl.c:123 [inline] RIP: 0010:put_links+0x19e/0x4f0 fs/proc/proc_sysctl.c:1472 Code: 0f 84 33 02 00 00 49 8d 5f 18 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 bc 94 c6 ff 48 8b 1b 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 a3 94 c6 ff 48 8b 2b 48 89 5c 24 RSP: 0018:ffffc9000bf87980 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888026909e00 RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000000 RBP: 000000000000000b R08: ffffffff822dc888 R09: ffffffff822dc93a R10: 0000000000000002 R11: ffff888026909e00 R12: ffffffff8d9d70d0 R13: dffffc0000000000 R14: ffffffff8ba0d080 R15: ffff888018108058 FS: 0000000000000000(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f4e64ba9930 CR3: 0000000020a88000 CR4: 0000000000350ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 ---------------- Code disassembly (best guess): 0: 0f 84 33 02 00 00 je 0x239 6: 49 8d 5f 18 lea 0x18(%r15),%rbx a: 48 89 d8 mov %rbx,%rax d: 48 c1 e8 03 shr $0x3,%rax 11: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) 16: 74 08 je 0x20 18: 48 89 df mov %rbx,%rdi 1b: e8 bc 94 c6 ff call 0xffc694dc 20: 48 8b 1b mov (%rbx),%rbx 23: 48 89 d8 mov %rbx,%rax 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction 2f: 74 08 je 0x39 31: 48 89 df mov %rbx,%rdi 34: e8 a3 94 c6 ff call 0xffc694dc 39: 48 8b 2b mov (%rbx),%rbp 3c: 48 rex.W 3d: 89 .byte 0x89 3e: 5c pop %rsp 3f: 24 .byte 0x24 -- Yours sincerely, Xingyu
