CVE-2024-44987

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

ipv6: prevent UAF in ip6_send_skb()

syzbot reported an UAF in ip6_send_skb() [1]

After ip6_local_out() has returned, we no longer can safely

dereference rt, unless we hold rcu_read_lock().

A similar issue has been fixed in commit

a688caa34beb ("ipv6: take rcu lock in rawv6_send_hdrinc()")

Another potential issue in ip6_finish_output2() is handled in a

separate patch.

[1]

BUG: KASAN: slab-use-after-free in ip6_send_skb+0x18d/0x230 net/ipv6/ip6_output.c:1964

Read of size 8 at addr ffff88806dde4858 by task syz.1.380/6530

CPU: 1 UID: 0 PID: 6530 Comm: syz.1.380 Not tainted 6.11.0-rc3-syzkaller-00306-gdf6cbc62cc9b #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024

Call Trace:

<TASK>

__dump_stack lib/dump_stack.c:93 [inline]

dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119

print_address_description mm/kasan/report.c:377 [inline]

print_report+0x169/0x550 mm/kasan/report.c:488

kasan_report+0x143/0x180 mm/kasan/report.c:601

ip6_send_skb+0x18d/0x230 net/ipv6/ip6_output.c:1964

rawv6_push_pending_frames+0x75c/0x9e0 net/ipv6/raw.c:588

rawv6_sendmsg+0x19c7/0x23c0 net/ipv6/raw.c:926

sock_sendmsg_nosec net/socket.c:730 [inline]

__sock_sendmsg+0x1a6/0x270 net/socket.c:745

sock_write_iter+0x2dd/0x400 net/socket.c:1160

do_iter_readv_writev+0x60a/0x890

vfs_writev+0x37c/0xbb0 fs/read_write.c:971

do_writev+0x1b1/0x350 fs/read_write.c:1018

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x77/0x7f

RIP: 0033:0x7f936bf79e79

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:00007f936cd7f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014

RAX: ffffffffffffffda RBX: 00007f936c115f80 RCX: 00007f936bf79e79

RDX: 0000000000000001 RSI: 0000000020000040 RDI: 0000000000000004

RBP: 00007f936bfe7916 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 0000000000000000 R14: 00007f936c115f80 R15: 00007fff2860a7a8

</TASK>

Allocated by task 6530:

kasan_save_stack mm/kasan/common.c:47 [inline]

kasan_save_track+0x3f/0x80 mm/kasan/common.c:68

unpoison_slab_object mm/kasan/common.c:312 [inline]

__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338

kasan_slab_alloc include/linux/kasan.h:201 [inline]

slab_post_alloc_hook mm/slub.c:3988 [inline]

slab_alloc_node mm/slub.c:4037 [inline]

kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4044

dst_alloc+0x12b/0x190 net/core/dst.c:89

ip6_blackhole_route+0x59/0x340 net/ipv6/route.c:2670

make_blackhole net/xfrm/xfrm_policy.c:3120 [inline]

xfrm_lookup_route+0xd1/0x1c0 net/xfrm/xfrm_policy.c:3313

ip6_dst_lookup_flow+0x13e/0x180 net/ipv6/ip6_output.c:1257

rawv6_sendmsg+0x1283/0x23c0 net/ipv6/raw.c:898

sock_sendmsg_nosec net/socket.c:730 [inline]

__sock_sendmsg+0x1a6/0x270 net/socket.c:745

____sys_sendmsg+0x525/0x7d0 net/socket.c:2597

___sys_sendmsg net/socket.c:2651 [inline]

__sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680

do_syscall_x64 arch/x86/entry/common.c:52 [inline]

do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83

entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 45:

kasan_save_stack mm/kasan/common.c:47 [inline]

kasan_save_track+0x3f/0x80 mm/kasan/common.c:68

kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579

poison_slab_object+0xe0/0x150 mm/kasan/common.c:240

__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256

kasan_slab_free include/linux/kasan.h:184 [inline]

slab_free_hook mm/slub.c:2252 [inline]

slab_free mm/slub.c:4473 [inline]

kmem_cache_free+0x145/0x350 mm/slub.c:4548

dst_destroy+0x2ac/0x460 net/core/dst.c:124

rcu_do_batch kernel/rcu/tree.c:2569 [inline]

rcu_core+0xafd/0x1830 kernel/rcu/tree.

---truncated---