CVE-2024-40954

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

net: do not leave a dangling sk pointer, when socket creation fails

It is possible to trigger a use-after-free by:

* attaching an fentry probe to __sock_release() and the probe calling the

bpf_get_socket_cookie() helper

* running traceroute -I 1.1.1.1 on a freshly booted VM

A KASAN enabled kernel will log something like below (decoded and stripped):

==================================================================

BUG: KASAN: slab-use-after-free in __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)

Read of size 8 at addr ffff888007110dd8 by task traceroute/299

CPU: 2 PID: 299 Comm: traceroute Tainted: G E 6.10.0-rc2+ #2

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014

Call Trace:

<TASK>

dump_stack_lvl (lib/dump_stack.c:117 (discriminator 1))

print_report (mm/kasan/report.c:378 mm/kasan/report.c:488)

? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)

kasan_report (mm/kasan/report.c:603)

? __sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)

kasan_check_range (mm/kasan/generic.c:183 mm/kasan/generic.c:189)

__sock_gen_cookie (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-instrumented.h:1611 net/core/sock_diag.c:29)

bpf_get_socket_ptr_cookie (./arch/x86/include/asm/preempt.h:94 ./include/linux/sock_diag.h:42 net/core/filter.c:5094 net/core/filter.c:5092)

bpf_prog_875642cf11f1d139___sock_release+0x6e/0x8e

bpf_trampoline_6442506592+0x47/0xaf

__sock_release (net/socket.c:652)

__sock_create (net/socket.c:1601)

...

Allocated by task 299 on cpu 2 at 78.328492s:

kasan_save_stack (mm/kasan/common.c:48)

kasan_save_track (mm/kasan/common.c:68)

__kasan_slab_alloc (mm/kasan/common.c:312 mm/kasan/common.c:338)

kmem_cache_alloc_noprof (mm/slub.c:3941 mm/slub.c:4000 mm/slub.c:4007)

sk_prot_alloc (net/core/sock.c:2075)

sk_alloc (net/core/sock.c:2134)

inet_create (net/ipv4/af_inet.c:327 net/ipv4/af_inet.c:252)

__sock_create (net/socket.c:1572)

__sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)

__x64_sys_socket (net/socket.c:1718)

do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Freed by task 299 on cpu 2 at 78.328502s:

kasan_save_stack (mm/kasan/common.c:48)

kasan_save_track (mm/kasan/common.c:68)

kasan_save_free_info (mm/kasan/generic.c:582)

poison_slab_object (mm/kasan/common.c:242)

__kasan_slab_free (mm/kasan/common.c:256)

kmem_cache_free (mm/slub.c:4437 mm/slub.c:4511)

__sk_destruct (net/core/sock.c:2117 net/core/sock.c:2208)

inet_create (net/ipv4/af_inet.c:397 net/ipv4/af_inet.c:252)

__sock_create (net/socket.c:1572)

__sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)

__x64_sys_socket (net/socket.c:1718)

do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)

entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Fix this by clearing the struct socket reference in sk_common_release() to cover

all protocol families create functions, which may already attached the

reference to the sk object with sock_init_data().