CVE-2024-40954 net: do not leave a dangling sk pointer, when socket creation fails
A use-after-free in the Linux kernel network stack allows attackers with BPF probe access to cause crashes or potentially execute code.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-40954?
CVE-2024-40954 is a high-severity use after free vulnerability in Linux kernel, published on 12 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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().
Weakness: CWE-416
Which versions are affected by CVE-2024-40954?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-40954?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-40954 being exploited?
There is no known exploitation of CVE-2024-40954 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-40954, DEBIAN-CVE-2024-40954, GHSA-68p8-jjxw-w2v4, ROOT-OS-UBUNTU-2204-CVE-2024-40954, ROOT-OS-UBUNTU-2404-CVE-2024-40954, UBUNTU-CVE-2024-40954.