kAFS: bad VL server IP address BUG: unable to handle page fault for address: fffffffffffffffa #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD e387067 P4D e387067 PUD e389067 PMD 0 Oops: Oops: 0002 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 6599 Comm: syz.0.16 Not tainted 6.16.0-rc4-syzkaller-g66701750d556 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 RIP: 0010:arch_atomic_fetch_add arch/x86/include/asm/atomic.h:93 [inline] RIP: 0010:raw_atomic_fetch_sub_release include/linux/atomic/atomic-arch-fallback.h:949 [inline] RIP: 0010:atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:401 [inline] RIP: 0010:__refcount_sub_and_test include/linux/refcount.h:389 [inline] RIP: 0010:__refcount_dec_and_test include/linux/refcount.h:432 [inline] RIP: 0010:refcount_dec_and_test include/linux/refcount.h:450 [inline] RIP: 0010:afs_put_vlserverlist+0x3a/0x220 fs/afs/vl_list.c:67 Code: 53 48 83 ec 18 e8 b6 45 2b fe 48 85 ed 74 43 e8 ac 45 2b fe 4c 8d 65 10 be 04 00 00 00 bb ff ff ff ff 4c 89 e7 e8 b6 30 91 fe 0f c1 5d 10 31 ff 89 de e8 c8 40 2b fe 85 db 7e 29 e8 7f 45 2b RSP: 0018:ffffc90003107ae0 EFLAGS: 00010246 RAX: 0000000000000001 RBX: 00000000ffffffff RCX: ffffffff8390478a RDX: fffffc0000000000 RSI: 0000000000000004 RDI: fffffffffffffffa RBP: ffffffffffffffea R08: 0000000000000001 R09: fffffbffffffffff R10: fffffffffffffffd R11: 0000000000000001 R12: fffffffffffffffa R13: ffffffffffffffea R14: ffff888028a5af00 R15: ffff8880748eb000 FS: 00007ff59e5b16c0(0000) GS:ffff88812475f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffffffffffffa CR3: 0000000036a26000 CR4: 00000000003526f0 Call Trace: afs_alloc_cell fs/afs/cell.c:218 [inline] afs_lookup_cell+0x12a5/0x1680 fs/afs/cell.c:264 afs_cell_init+0x17a/0x380 fs/afs/cell.c:386 afs_proc_rootcell_write+0x21f/0x290 fs/afs/proc.c:247 proc_simple_write+0x117/0x1b0 fs/proc/generic.c:825 pde_write fs/proc/inode.c:330 [inline] proc_reg_write+0x23d/0x330 fs/proc/inode.c:342 vfs_write+0x29d/0x1150 fs/read_write.c:684 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ff59d78d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ff59e5b1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007ff59d9a5fa0 RCX: 00007ff59d78d169 RDX: 000000000000009e RSI: 0000200000000200 RDI: 0000000000000003 RBP: 00007ff59d80e2a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007ff59d9a5fa0 R15: 00007ffe12c4e878 Modules linked in: CR2: fffffffffffffffa ---[ end trace 0000000000000000 ]--- RIP: 0010:arch_atomic_fetch_add arch/x86/include/asm/atomic.h:93 [inline] RIP: 0010:raw_atomic_fetch_sub_release include/linux/atomic/atomic-arch-fallback.h:949 [inline] RIP: 0010:atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:401 [inline] RIP: 0010:__refcount_sub_and_test include/linux/refcount.h:389 [inline] RIP: 0010:__refcount_dec_and_test include/linux/refcount.h:432 [inline] RIP: 0010:refcount_dec_and_test include/linux/refcount.h:450 [inline] RIP: 0010:afs_put_vlserverlist+0x3a/0x220 fs/afs/vl_list.c:67 Code: 53 48 83 ec 18 e8 b6 45 2b fe 48 85 ed 74 43 e8 ac 45 2b fe 4c 8d 65 10 be 04 00 00 00 bb ff ff ff ff 4c 89 e7 e8 b6 30 91 fe 0f c1 5d 10 31 ff 89 de e8 c8 40 2b fe 85 db 7e 29 e8 7f 45 2b RSP: 0018:ffffc90003107ae0 EFLAGS: 00010246 RAX: 0000000000000001 RBX: 00000000ffffffff RCX: ffffffff8390478a RDX: fffffc0000000000 RSI: 0000000000000004 RDI: fffffffffffffffa RBP: ffffffffffffffea R08: 0000000000000001 R09: fffffbffffffffff R10: fffffffffffffffd R11: 0000000000000001 R12: fffffffffffffffa R13: ffffffffffffffea R14: ffff888028a5af00 R15: ffff8880748eb000 FS: 00007ff59e5b16c0(0000) GS:ffff88812475f000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffffffffffffa CR3: 0000000036a26000 CR4: 00000000003526f0 ---------------- Code disassembly (best guess): 0: 53 push %rbx 1: 48 83 ec 18 sub $0x18,%rsp 5: e8 b6 45 2b fe call 0xfe2b45c0 a: 48 85 ed test %rbp,%rbp d: 74 43 je 0x52 f: e8 ac 45 2b fe call 0xfe2b45c0 14: 4c 8d 65 10 lea 0x10(%rbp),%r12 18: be 04 00 00 00 mov $0x4,%esi 1d: bb ff ff ff ff mov $0xffffffff,%ebx 22: 4c 89 e7 mov %r12,%rdi 25: e8 b6 30 91 fe call 0xfe9130e0 * 2a: f0 0f c1 5d 10 lock xadd %ebx,0x10(%rbp) <-- trapping instruction 2f: 31 ff xor %edi,%edi 31: 89 de mov %ebx,%esi 33: e8 c8 40 2b fe call 0xfe2b4100 38: 85 db test %ebx,%ebx 3a: 7e 29 jle 0x65 3c: e8 .byte 0xe8 3d: 7f 45 jg 0x84 3f: 2b .byte 0x2b