CVE-2024-56646 — ipv6: avoid possible NULL deref in modify_prefix_route()

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

ipv6: avoid possible NULL deref in modify_prefix_route()

syzbot found a NULL deref [1] in modify_prefix_route(), caused by one fib6_info without a fib6_table pointer set.

This can happen for net->ipv6.fib6_null_entry

[1] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] CPU: 1 UID: 0 PID: 5837 Comm: syz-executor888 Not tainted 6.12.0-syzkaller-09567-g7eef7e306d3c #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 RIP: 0010:__lock_acquire+0xe4/0x3c40 kernel/locking/lockdep.c:5089 Code: 08 84 d2 0f 85 15 14 00 00 44 8b 0d ca 98 f5 0e 45 85 c9 0f 84 b4 0e 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 96 2c 00 00 49 8b 04 24 48 3d a0 07 7f 93 0f 84 RSP: 0018:ffffc900035d7268 EFLAGS: 00010006 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000006 RSI: 1ffff920006bae5f RDI: 0000000000000030 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 R10: ffffffff90608e17 R11: 0000000000000001 R12: 0000000000000030 R13: ffff888036334880 R14: 0000000000000000 R15: 0000000000000000 FS: 0000555579e90380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc59cc4278 CR3: 0000000072b54000 CR4: 00000000…

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CVE-2024-56646 — ipv6: avoid possible NULL deref in modify_prefix_route()