In the Linux kernel, the following vulnerability has been resolved: ipv6: avoid possible NULL deref in rt6uncachedlistflushdev() Blamed commit accidentally removed a check for rt->rt6iidev being NULL, as spotted by syzbot: 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: 1 UID: 0 PID: 10998 Comm: syz-executor Not tainted 6.11.0-rc6-syzkaller-00208-g625403177711 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 RIP: 0010:rt6uncachedlistflushdev net/ipv6/route.c:177 [inline] RIP: 0010:rt6disableip+0x33e/0x7e0 net/ipv6/route.c:4914 Code: 41 80 3c 04 00 74 0a e8 90 d0 9b f7 48 8b 7c 24 08 48 8b 07 48 89 44 24 10 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 64 d0 9b f7 48 8b 44 24 18 49 39 06 RSP: 0018:ffffc900047374e0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 1ffff1100fdf8f33 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88807efc78c0 RBP: ffffc900047375d0 R08: 0000000000000003 R09: fffff520008e6e8c R10: dffffc0000000000 R11: fffff520008e6e8c R12: 1ffff1100fdf8f18 R13: ffff88807efc7998 R14: 0000000000000000 R15: ffff88807efc7930 FS: 0000000000000000(0000) GS:ffff8880b8900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020002a80 CR3: 0000000022f62000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> addrconfifdown+0x15d/0x1bd0 net/ipv6/addrconf.c:3856 addrconfnotify+0x3cb/0x1020 notifiercallchain+0x19f/0x3e0 kernel/notifier.c:93 callnetdevicenotifiersextack net/core/dev.c:2032 [inline] callnetdevicenotifiers net/core/dev.c:2046 [inline] unregisternetdevicemanynotify+0xd81/0x1c40 net/core/dev.c:11352 unregisternetdevicemany net/core/dev.c:11414 [inline] unregisternetdevicequeue+0x303/0x370 net/core/dev.c:11289 unregisternetdevice include/linux/netdevice.h:3129 [inline] _tundetach+0x6b9/0x1600 drivers/net/tun.c:685 tundetach drivers/net/tun.c:701 [inline] tunchrclose+0x108/0x1b0 drivers/net/tun.c:3510 _fput+0x24a/0x8a0 fs/filetable.c:422 taskworkrun+0x24f/0x310 kernel/taskwork.c:228 exittaskwork include/linux/taskwork.h:40 [inline] doexit+0xa2f/0x27f0 kernel/exit.c:882 dogroupexit+0x207/0x2c0 kernel/exit.c:1031 _dosysexitgroup kernel/exit.c:1042 [inline] _sesysexitgroup kernel/exit.c:1040 [inline] _x64sysexitgroup+0x3f/0x40 kernel/exit.c:1040 x64syscall+0x2634/0x2640 arch/x86/include/generated/asm/syscalls64.h:232 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xf3/0x230 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f RIP: 0033:0x7f1acc77def9 Code: Unable to access opcode bytes at 0x7f1acc77decf. RSP: 002b:00007ffeb26fa738 EFLAGS: 00000246 ORIGRAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1acc77def9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043 RBP: 00007f1acc7dd508 R08: 00007ffeb26f84d7 R09: 0000000000000003 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000003 R14: 00000000ffffffff R15: 00007ffeb26fa8e0 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:rt6uncachedlistflushdev net/ipv6/route.c:177 [inline] RIP: 0010:rt6disableip+0x33e/0x7e0 net/ipv6/route.c:4914 Code: 41 80 3c 04 00 74 0a e8 90 d0 9b f7 48 8b 7c 24 08 48 8b 07 48 89 44 24 10 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 64 d0 9b f7 48 8b 44 24 18 49 39 06 RSP: 0018:ffffc900047374e0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 1ffff1100fdf8f33 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88807efc78c0 R ---truncated---