CVE-2024-26852: net/ipv6: avoid possible UAF in ip6_route_mpath_notify()

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

net/ipv6: avoid possible UAF in ip6routempathnotify()

syzbot found another use-after-free in ip6routempathnotify() [1]

Commit f7225172f25a ("net/ipv6: prevent use after free in ip6routempathnotify") was not able to fix the root cause.

We need to defer the fib6inforelease() calls after ip6routempathnotify(), in the cleanup phase.

[1] BUG: KASAN: slab-use-after-free in rt6fillnode+0x1460/0x1ac0 Read of size 4 at addr ffff88809a07fc64 by task syz-executor.2/23037

CPU: 0 PID: 23037 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-01035-gea7f3cfaa588 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024 Call Trace: <TASK> dumpstack lib/dumpstack.c:88 [inline] dumpstacklvl+0x1e7/0x2e0 lib/dumpstack.c:106 printaddressdescription mm/kasan/report.c:377 [inline] printreport+0x167/0x540 mm/kasan/report.c:488 kasanreport+0x142/0x180 mm/kasan/report.c:601 rt6fillnode+0x1460/0x1ac0 inet6rtnotify+0x13b/0x290 net/ipv6/route.c:6184 ip6routempathnotify net/ipv6/route.c:5198 [inline] ip6routemultipathadd net/ipv6/route.c:5404 [inline] inet6rtmnewroute+0x1d0f/0x2300 net/ipv6/route.c:5517 rtnetlinkrcvmsg+0x885/0x1040 net/core/rtnetlink.c:6597 netlinkrcvskb+0x1e3/0x430 net/netlink/afnetlink.c:2543 netlinkunicastkernel net/netlink/afnetlink.c:1341 [inline] netlinkunicast+0x7ea/0x980 net/netlink/afnetlink.c:1367 netlinksendmsg+0xa3b/0xd70 net/netlink/afnetlink.c:1908 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x221/0x270 net/socket.c:745 syssendmsg+0x525/0x7d0 net/socket.c:2584 syssendmsg net/socket.c:2638 [inline] syssendmsg+0x2b0/0x3a0 net/socket.c:2667 dosyscall64+0xf9/0x240 entrySYSCALL64afterhwframe+0x6f/0x77 RIP: 0033:0x7f73dd87dda9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f73de6550c8 EFLAGS: 00000246 ORIGRAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f73dd9ac050 RCX: 00007f73dd87dda9 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005 RBP: 00007f73dd8ca47a R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000006e R14: 00007f73dd9ac050 R15: 00007ffdbdeb7858 </TASK>

Allocated by task 23037: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3f/0x80 mm/kasan/common.c:68 poisonkmallocredzone mm/kasan/common.c:372 [inline] kasankmalloc+0x98/0xb0 mm/kasan/common.c:389 kasankmalloc include/linux/kasan.h:211 [inline] dokmallocnode mm/slub.c:3981 [inline] kmalloc+0x22e/0x490 mm/slub.c:3994 kmalloc include/linux/slab.h:594 [inline] kzalloc include/linux/slab.h:711 [inline] fib6infoalloc+0x2e/0xf0 net/ipv6/ip6fib.c:155 ip6routeinfocreate+0x445/0x12b0 net/ipv6/route.c:3758 ip6routemultipathadd net/ipv6/route.c:5298 [inline] inet6rtmnewroute+0x744/0x2300 net/ipv6/route.c:5517 rtnetlinkrcvmsg+0x885/0x1040 net/core/rtnetlink.c:6597 netlinkrcvskb+0x1e3/0x430 net/netlink/afnetlink.c:2543 netlinkunicastkernel net/netlink/afnetlink.c:1341 [inline] netlinkunicast+0x7ea/0x980 net/netlink/afnetlink.c:1367 netlinksendmsg+0xa3b/0xd70 net/netlink/afnetlink.c:1908 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x221/0x270 net/socket.c:745 syssendmsg+0x525/0x7d0 net/socket.c:2584 syssendmsg net/socket.c:2638 [inline] syssendmsg+0x2b0/0x3a0 net/socket.c:2667 dosyscall64+0xf9/0x240 entrySYSCALL64afterhwframe+0x6f/0x77

Freed by task 16: kasansavestack mm/kasan/common.c:47 [inline] kasansavetrack+0x3f/0x80 mm/kasan/common.c:68 kasansavefreeinfo+0x4e/0x60 mm/kasan/generic.c:640 poisonslabobject+0xa6/0xe0 m ---truncated---

— NVD

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

net/ipv6: avoid possible UAF in ip6routempathnotify()

The Linux kernel CVE team has assigned CVE-2024-26852 to this issue.

Upstream advisory: https://lore.kernel.org/linux-cve-announce/2024041723-CVE-2024-26852-0057@gregkh/T

— Red Hat