CVE-2024-35886

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

ipv6: Fix infinite recursion in fib6_dump_done().

syzkaller reported infinite recursive calls of fib6_dump_done() during

netlink socket destruction. [1]

From the log, syzkaller sent an AF_UNSPEC RTM_GETROUTE message, and then

the response was generated. The following recvmmsg() resumed the dump

for IPv6, but the first call of inet6_dump_fib() failed at kzalloc() due

to the fault injection. [0]

12:01:34 executing program 3:

r0 = socket$nl_route(0x10, 0x3, 0x0)

sendmsg$nl_route(r0, ... snip ...)

recvmmsg(r0, ... snip ...) (fail_nth: 8)

Here, fib6_dump_done() was set to nlk_sk(sk)->cb.done, and the next call

of inet6_dump_fib() set it to nlk_sk(sk)->cb.args[3]. syzkaller stopped

receiving the response halfway through, and finally netlink_sock_destruct()

called nlk_sk(sk)->cb.done().

fib6_dump_done() calls fib6_dump_end() and nlk_sk(sk)->cb.done() if it

is still not NULL. fib6_dump_end() rewrites nlk_sk(sk)->cb.done() by

nlk_sk(sk)->cb.args[3], but it has the same function, not NULL, calling

itself recursively and hitting the stack guard page.

To avoid the issue, let's set the destructor after kzalloc().

[0]:

FAULT_INJECTION: forcing a failure.

name failslab, interval 1, probability 0, space 0, times 0

CPU: 1 PID: 432110 Comm: syz-executor.3 Not tainted 6.8.0-12821-g537c2e91d354-dirty #11

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Call Trace:

<TASK>

dump_stack_lvl (lib/dump_stack.c:117)

should_fail_ex (lib/fault-inject.c:52 lib/fault-inject.c:153)

should_failslab (mm/slub.c:3733)

kmalloc_trace (mm/slub.c:3748 mm/slub.c:3827 mm/slub.c:3992)

inet6_dump_fib (./include/linux/slab.h:628 ./include/linux/slab.h:749 net/ipv6/ip6_fib.c:662)

rtnl_dump_all (net/core/rtnetlink.c:4029)

netlink_dump (net/netlink/af_netlink.c:2269)

netlink_recvmsg (net/netlink/af_netlink.c:1988)

____sys_recvmsg (net/socket.c:1046 net/socket.c:2801)

___sys_recvmsg (net/socket.c:2846)

do_recvmmsg (net/socket.c:2943)

__x64_sys_recvmmsg (net/socket.c:3041 net/socket.c:3034 net/socket.c:3034)

[1]:

BUG: TASK stack guard page was hit at 00000000f2fa9af1 (stack is 00000000b7912430..000000009a436beb)

stack guard page: 0000 [#1] PREEMPT SMP KASAN

CPU: 1 PID: 223719 Comm: kworker/1:3 Not tainted 6.8.0-12821-g537c2e91d354-dirty #11

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Workqueue: events netlink_sock_destruct_work

RIP: 0010:fib6_dump_done (net/ipv6/ip6_fib.c:570)

Code: 3c 24 e8 f3 e9 51 fd e9 28 fd ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 41 57 41 56 41 55 41 54 55 48 89 fd <53> 48 8d 5d 60 e8 b6 4d 07 fd 48 89 da 48 b8 00 00 00 00 00 fc ff

RSP: 0018:ffffc9000d980000 EFLAGS: 00010293

RAX: 0000000000000000 RBX: ffffffff84405990 RCX: ffffffff844059d3

RDX: ffff8881028e0000 RSI: ffffffff84405ac2 RDI: ffff88810c02f358

RBP: ffff88810c02f358 R08: 0000000000000007 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000224 R12: 0000000000000000

R13: ffff888007c82c78 R14: ffff888007c82c68 R15: ffff888007c82c68

FS: 0000000000000000(0000) GS:ffff88811b100000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: ffffc9000d97fff8 CR3: 0000000102309002 CR4: 0000000000770ef0

PKRU: 55555554

Call Trace:

<#DF>

</#DF>

<TASK>

fib6_dump_done (net/ipv6/ip6_fib.c:572 (discriminator 1))

fib6_dump_done (net/ipv6/ip6_fib.c:572 (discriminator 1))

...

fib6_dump_done (net/ipv6/ip6_fib.c:572 (discriminator 1))

fib6_dump_done (net/ipv6/ip6_fib.c:572 (discriminator 1))

netlink_sock_destruct (net/netlink/af_netlink.c:401)

__sk_destruct (net/core/sock.c:2177 (discriminator 2))

sk_destruct (net/core/sock.c:2224)

__sk_free (net/core/sock.c:2235)

sk_free (net/core/sock.c:2246)

process_one_work (kernel/workqueue.c:3259)

worker_thread (kernel/workqueue.c:3329 kernel/workqueue.

---truncated---