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Message-ID: <20240617203050.84843-1-kuniyu@amazon.com>
Date: Mon, 17 Jun 2024 13:30:50 -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 v2] net: do not leave a dangling sk pointer, when socket creation fails
From: Ignat Korchagin <ignat@...udflare.com>
Date: Mon, 17 Jun 2024 20:59:34 +0100
> A KASAN enabled kernel will log something like below (decoded and stripped):
> [ 78.328507][ T299] ==================================================================
> [ 78.329018][ T299] 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)
> [ 78.329366][ T299] Read of size 8 at addr ffff888007110dd8 by task traceroute/299
> [ 78.329366][ T299]
> [ 78.329366][ T299] CPU: 2 PID: 299 Comm: traceroute Tainted: G E 6.10.0-rc2+ #2
> [ 78.329366][ T299] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> [ 78.329366][ T299] Call Trace:
> [ 78.329366][ T299] <TASK>
> [ 78.329366][ T299] dump_stack_lvl (lib/dump_stack.c:117 (discriminator 1))
> [ 78.329366][ T299] print_report (mm/kasan/report.c:378 mm/kasan/report.c:488)
> [ 78.329366][ T299] ? __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)
> [ 78.329366][ T299] kasan_report (mm/kasan/report.c:603)
> [ 78.329366][ T299] ? __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)
> [ 78.329366][ T299] kasan_check_range (mm/kasan/generic.c:183 mm/kasan/generic.c:189)
> [ 78.329366][ T299] __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)
> [ 78.329366][ T299] 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)
> [ 78.329366][ T299] bpf_prog_875642cf11f1d139___sock_release+0x6e/0x8e
> [ 78.329366][ T299] bpf_trampoline_6442506592+0x47/0xaf
> [ 78.329366][ T299] __sock_release (net/socket.c:652)
> [ 78.329366][ T299] __sock_create (net/socket.c:1601)
> ...
> [ 78.329366][ T299] Allocated by task 299 on cpu 2 at 78.328492s:
> [ 78.329366][ T299] kasan_save_stack (mm/kasan/common.c:48)
> [ 78.329366][ T299] kasan_save_track (mm/kasan/common.c:68)
> [ 78.329366][ T299] __kasan_slab_alloc (mm/kasan/common.c:312 mm/kasan/common.c:338)
> [ 78.329366][ T299] kmem_cache_alloc_noprof (mm/slub.c:3941 mm/slub.c:4000 mm/slub.c:4007)
> [ 78.329366][ T299] sk_prot_alloc (net/core/sock.c:2075)
> [ 78.329366][ T299] sk_alloc (net/core/sock.c:2134)
> [ 78.329366][ T299] inet_create (net/ipv4/af_inet.c:327 net/ipv4/af_inet.c:252)
> [ 78.329366][ T299] __sock_create (net/socket.c:1572)
> [ 78.329366][ T299] __sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)
> [ 78.329366][ T299] __x64_sys_socket (net/socket.c:1718)
> [ 78.329366][ T299] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
> [ 78.329366][ T299] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
> [ 78.329366][ T299]
> [ 78.329366][ T299] Freed by task 299 on cpu 2 at 78.328502s:
> [ 78.329366][ T299] kasan_save_stack (mm/kasan/common.c:48)
> [ 78.329366][ T299] kasan_save_track (mm/kasan/common.c:68)
> [ 78.329366][ T299] kasan_save_free_info (mm/kasan/generic.c:582)
> [ 78.329366][ T299] poison_slab_object (mm/kasan/common.c:242)
> [ 78.329366][ T299] __kasan_slab_free (mm/kasan/common.c:256)
> [ 78.329366][ T299] kmem_cache_free (mm/slub.c:4437 mm/slub.c:4511)
> [ 78.329366][ T299] __sk_destruct (net/core/sock.c:2117 net/core/sock.c:2208)
> [ 78.329366][ T299] inet_create (net/ipv4/af_inet.c:397 net/ipv4/af_inet.c:252)
> [ 78.329366][ T299] __sock_create (net/socket.c:1572)
> [ 78.329366][ T299] __sys_socket (net/socket.c:1660 net/socket.c:1644 net/socket.c:1706)
> [ 78.329366][ T299] __x64_sys_socket (net/socket.c:1718)
> [ 78.329366][ T299] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
> [ 78.329366][ T299] 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.
>
> 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/
> ---
> Changes in v2:
> * moved the NULL-ing of the socket reference to sk_common_release() (as
> suggested by Kuniyuki Iwashima)
> * trimmed down the KASAN report in the commit message to show only relevant
> info
It seems the most important repro was lost. I'd like to keep that
in the commit message so that we can easily understand the Fixes:
tag and how the issue happens.
While at it, could you remove the timestamp and thread id in KASAN
splat ?
>
> net/core/sock.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 8629f9aecf91..575af557c46b 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -3742,6 +3742,17 @@ void sk_common_release(struct sock *sk)
>
> sk->sk_prot->unhash(sk);
>
> + /*
> + * struct net_proto_family create functions like inet_create() or
nit: This should be netdev style:
/* struct net_proto_family ...
* ...
*/
See: Documentation/process/maintainer-netdev.rst
But I think the comment is not needed here if the commit message has
* KASAN splat
* How the problem happens
* run bpf_get_socket_cookie() in __sock_release()
* What the problem is
* UAF happens if pf->create() fails after calling sock_init_data()
, we can just git-blame the change below.
Thanks!
> + * inet6_create() have an error path, which call this function. This sk
> + * may have already been associated with a struct socket, so ensure to
> + * clear this reference not to leave a dangling pointer in the
> + * struct socket instance.
> + */
> +
> + if (sk->sk_socket)
> + sk->sk_socket->sk = NULL;
> +
> /*
> * In this point socket cannot receive new packets, but it is possible
> * that some packets are in flight because some CPU runs receiver and
> --
> 2.39.2
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