Re: [PATCH net,v4] net/smc: prevent NULL pointer dereference in txopt_get

D. Wythe
2024-08-14T13:11:50Z

On 8/14/24 6:49 PM, Jeongjun Park wrote:
> Since smc_inet6_prot does not initialize ipv6_pinfo_offset, inet6_create()
> copies an incorrect address value, sk + 0 (offset), to inet_sk(sk)->pinet6.
>
> In addition, since inet_sk(sk)->pinet6 and smc_sk(sk)->clcsock practically
> point to the same address, when smc_create_clcsk() stores the newly
> created clcsock in smc_sk(sk)->clcsock, inet_sk(sk)->pinet6 is corrupted
> into clcsock. This causes NULL pointer dereference and various other
> memory corruptions.
>
> To solve this, we need to add smc6_sock structure, initialize
> .ipv6_pinfo_offset, and modify smc_sock structure.
>
> [ 278.629552][T28696] ==================================================================
> [ 278.631367][T28696] BUG: KASAN: null-ptr-deref in txopt_get+0x102/0x430
> [ 278.632724][T28696] Read of size 4 at addr 0000000000000200 by task syz.0.2965/28696
> [ 278.634802][T28696]
> [ 278.635236][T28696] CPU: 0 UID: 0 PID: 28696 Comm: syz.0.2965 Not tainted 6.11.0-rc2 #3
> [ 278.637458][T28696] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> [ 278.639426][T28696] Call Trace:
> [ 278.639833][T28696] <TASK>
> [ 278.640190][T28696] dump_stack_lvl+0x116/0x1b0
> [ 278.640844][T28696] ? txopt_get+0x102/0x430
> [ 278.641620][T28696] kasan_report+0xbd/0xf0
> [ 278.642440][T28696] ? txopt_get+0x102/0x430
> [ 278.643291][T28696] kasan_check_range+0xf4/0x1a0
> [ 278.644163][T28696] txopt_get+0x102/0x430
> [ 278.644940][T28696] ? __pfx_txopt_get+0x10/0x10
> [ 278.645877][T28696] ? selinux_netlbl_socket_setsockopt+0x1d0/0x420
> [ 278.646972][T28696] calipso_sock_getattr+0xc6/0x3e0
> [ 278.647630][T28696] calipso_sock_getattr+0x4b/0x80
> [ 278.648349][T28696] netlbl_sock_getattr+0x63/0xc0
> [ 278.649318][T28696] selinux_netlbl_socket_setsockopt+0x1db/0x420
> [ 278.650471][T28696] ? __pfx_selinux_netlbl_socket_setsockopt+0x10/0x10
> [ 278.652217][T28696] ? find_held_lock+0x2d/0x120
> [ 278.652231][T28696] selinux_socket_setsockopt+0x66/0x90
> [ 278.652247][T28696] security_socket_setsockopt+0x57/0xb0
> [ 278.652278][T28696] do_sock_setsockopt+0xf2/0x480
> [ 278.652289][T28696] ? __pfx_do_sock_setsockopt+0x10/0x10
> [ 278.652298][T28696] ? __fget_files+0x24b/0x4a0
> [ 278.652308][T28696] ? __fget_light+0x177/0x210
> [ 278.652316][T28696] __sys_setsockopt+0x1a6/0x270
> [ 278.652328][T28696] ? __pfx___sys_setsockopt+0x10/0x10
> [ 278.661787][T28696] ? xfd_validate_state+0x5d/0x180
> [ 278.662821][T28696] __x64_sys_setsockopt+0xbd/0x160
> [ 278.663719][T28696] ? lockdep_hardirqs_on+0x7c/0x110
> [ 278.664690][T28696] do_syscall_64+0xcb/0x250
> [ 278.665507][T28696] entry_SYSCALL_64_after_hwframe+0x77/0x7f
> [ 278.666618][T28696] RIP: 0033:0x7fe87ed9712d
> [ 278.667236][T28696] Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8
> ff ff ff f7 d8 64 89 01 48
> [ 278.670801][T28696] RSP: 002b:00007fe87faa4fa8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> [ 278.671832][T28696] RAX: ffffffffffffffda RBX: 00007fe87ef35f80 RCX: 00007fe87ed9712d
> [ 278.672806][T28696] RDX: 0000000000000036 RSI: 0000000000000029 RDI: 0000000000000003
> [ 278.674263][T28696] RBP: 00007fe87ee1bd8a R08: 0000000000000018 R09: 0000000000000000
> [ 278.675967][T28696] R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000000000
> [ 278.677953][T28696] R13: 000000000000000b R14: 00007fe87ef35f80 R15: 00007fe87fa85000
> [ 278.679321][T28696] </TASK>
> [ 278.679917][T28696] ==================================================================
>
> Fixes: d25a92ccae6b ("net/smc: Introduce IPPROTO_SMC")
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---
> net/smc/smc.h | 5 ++++-
> net/smc/smc_inet.c | 8 +++++++-
> 2 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/net/smc/smc.h b/net/smc/smc.h
> index 34b781e463c4..0d67a02a6ab1 100644
> --- a/net/smc/smc.h
> +++ b/net/smc/smc.h
> @@ -283,7 +283,10 @@ struct smc_connection {
> };
>
> struct smc_sock { /* smc sock container */
> - struct sock sk;
> + union {
> + struct sock sk;
> + struct inet_sock inet;
> + };
> struct socket *clcsock; /* internal tcp socket */
> void (*clcsk_state_change)(struct sock *sk);
> /* original stat_change fct. */
> diff --git a/net/smc/smc_inet.c b/net/smc/smc_inet.c
> index bece346dd8e9..9e5eff8f5226 100644
> --- a/net/smc/smc_inet.c
> +++ b/net/smc/smc_inet.c
> @@ -60,6 +60,11 @@ static struct inet_protosw smc_inet_protosw = {
> };
>
> #if IS_ENABLED(CONFIG_IPV6)
> +struct smc6_sock {
> + struct smc_sock smc;
> + struct ipv6_pinfo inet6;
> +};
> +
> static struct proto smc_inet6_prot = {
> .name = "INET6_SMC",
> .owner = THIS_MODULE,
> @@ -67,9 +72,10 @@ static struct proto smc_inet6_prot = {
> .hash = smc_hash_sk,
> .unhash = smc_unhash_sk,
> .release_cb = smc_release_cb,
> - .obj_size = sizeof(struct smc_sock),
> + .obj_size = sizeof(struct smc6_sock),
> .h.smc_hash = &smc_v6_hashinfo,
> .slab_flags = SLAB_TYPESAFE_BY_RCU,
> + .ipv6_pinfo_offset = offsetof(struct smc6_sock, inet6),
> };
>
> static const struct proto_ops smc_inet6_stream_ops = {
> --

Hi Jeongjun,

Thanks for you efforts, it makes sense to me now. But I still need some
time to test it
entirely before adding a r-by.

I will appreciate for your patience.

Thanks,
D. Wythe