linux-kernel - Re: [PATCH net v3] net: do not leave a dangling sk pointer, when socket creation fails

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Date: Mon, 17 Jun 2024 14:15:04 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <ignat@...udflare.com>
CC: <davem@...emloft.net>, <dsahern@...nel.org>, <edumazet@...gle.com>,
	<kernel-team@...udflare.com>, <kuba@...nel.org>, <kuniyu@...zon.com>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>, <revest@...omium.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH net v3] net: do not leave a dangling sk pointer, when socket creation fails

From: Ignat Korchagin <ignat@...udflare.com>
Date: Mon, 17 Jun 2024 22:02:05 +0100
> 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().
> 
> Fixes: c5dbb89fc2ac ("bpf: Expose bpf_get_socket_cookie to tracing programs")
> Suggested-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> Signed-off-by: Ignat Korchagin <ignat@...udflare.com>
> Cc: stable@...r.kernel.org
> Link: https://lore.kernel.org/netdev/20240613194047.36478-1-kuniyu@amazon.com/T/

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Thanks!


P.S. next time, please make sure 24h pass before reposting for netdev.

  See: Documentation/process/maintainer-netdev.rst