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linux/kernel/bpf/bpf_lsm.c
Kui-Feng Lee 5416c9aea8 bpf: Fix the kernel crash caused by bpf_setsockopt(). 
The kernel crash was caused by a BPF program attached to the
"lsm_cgroup/socket_sock_rcv_skb" hook, which performed a call to
`bpf_setsockopt()` in order to set the TCP_NODELAY flag as an
example. Flags like TCP_NODELAY can prompt the kernel to flush a
socket's outgoing queue, and this hook
"lsm_cgroup/socket_sock_rcv_skb" is frequently triggered by
softirqs. The issue was that in certain circumstances, when
`tcp_write_xmit()` was called to flush the queue, it would also allow
BH (bottom-half) to run. This could lead to our program attempting to
flush the same socket recursively, which caused a `skbuff` to be
unlinked twice.

`security_sock_rcv_skb()` is triggered by `tcp_filter()`. This occurs
before the sock ownership is checked in `tcp_v4_rcv()`. Consequently,
if a bpf program runs on `security_sock_rcv_skb()` while under softirq
conditions, it may not possess the lock needed for `bpf_setsockopt()`,
thus presenting an issue.

The patch fixes this issue by ensuring that a BPF program attached to
the "lsm_cgroup/socket_sock_rcv_skb" hook is not allowed to call
`bpf_setsockopt()`.

The differences from v1 are
 - changing commit log to explain holding the lock of the sock,
 - emphasizing that TCP_NODELAY is not the only flag, and
 - adding the fixes tag.

v1: https://lore.kernel.org/bpf/20230125000244.1109228-1-kuifeng@meta.com/

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Fixes: 9113d7e48e ("bpf: expose bpf_{g,s}etsockopt to lsm cgroup")
Link: https://lore.kernel.org/r/20230127001732.4162630-1-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
2023-01-26 23:26:40 -08:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2020 Google LLC.
*/
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/binfmts.h>
#include <linux/lsm_hooks.h>
#include <linux/bpf_lsm.h>
#include <linux/kallsyms.h>
#include <linux/bpf_verifier.h>
#include <net/bpf_sk_storage.h>
#include <linux/bpf_local_storage.h>
#include <linux/btf_ids.h>
#include <linux/ima.h>
#include <linux/bpf-cgroup.h>
/* For every LSM hook that allows attachment of BPF programs, declare a nop
* function where a BPF program can be attached.
*/
#define LSM_HOOK(RET, DEFAULT, NAME, ...) \
noinline RET bpf_lsm_##NAME(__VA_ARGS__) \
{ \
return DEFAULT; \
}
#include <linux/lsm_hook_defs.h>
#undef LSM_HOOK
#define LSM_HOOK(RET, DEFAULT, NAME, ...) BTF_ID(func, bpf_lsm_##NAME)
BTF_SET_START(bpf_lsm_hooks)
#include <linux/lsm_hook_defs.h>
#undef LSM_HOOK
BTF_SET_END(bpf_lsm_hooks)
/* List of LSM hooks that should operate on 'current' cgroup regardless
* of function signature.
*/
BTF_SET_START(bpf_lsm_current_hooks)
/* operate on freshly allocated sk without any cgroup association */
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_sk_alloc_security)
BTF_ID(func, bpf_lsm_sk_free_security)
#endif
BTF_SET_END(bpf_lsm_current_hooks)
/* List of LSM hooks that trigger while the socket is properly locked.
*/
BTF_SET_START(bpf_lsm_locked_sockopt_hooks)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_sock_graft)
BTF_ID(func, bpf_lsm_inet_csk_clone)
BTF_ID(func, bpf_lsm_inet_conn_established)
#endif
BTF_SET_END(bpf_lsm_locked_sockopt_hooks)
/* List of LSM hooks that trigger while the socket is _not_ locked,
* but it's ok to call bpf_{g,s}etsockopt because the socket is still
* in the early init phase.
*/
BTF_SET_START(bpf_lsm_unlocked_sockopt_hooks)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_socket_post_create)
BTF_ID(func, bpf_lsm_socket_socketpair)
#endif
BTF_SET_END(bpf_lsm_unlocked_sockopt_hooks)
#ifdef CONFIG_CGROUP_BPF
void bpf_lsm_find_cgroup_shim(const struct bpf_prog *prog,
bpf_func_t *bpf_func)
{
const struct btf_param *args __maybe_unused;
if (btf_type_vlen(prog->aux->attach_func_proto) < 1 ||
btf_id_set_contains(&bpf_lsm_current_hooks,
prog->aux->attach_btf_id)) {
*bpf_func = __cgroup_bpf_run_lsm_current;
return;
}
#ifdef CONFIG_NET
args = btf_params(prog->aux->attach_func_proto);
if (args[0].type == btf_sock_ids[BTF_SOCK_TYPE_SOCKET])
*bpf_func = __cgroup_bpf_run_lsm_socket;
else if (args[0].type == btf_sock_ids[BTF_SOCK_TYPE_SOCK])
*bpf_func = __cgroup_bpf_run_lsm_sock;
else
#endif
*bpf_func = __cgroup_bpf_run_lsm_current;
}
#endif
int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
const struct bpf_prog *prog)
{
if (!prog->gpl_compatible) {
bpf_log(vlog,
"LSM programs must have a GPL compatible license\n");
return -EINVAL;
}
if (!btf_id_set_contains(&bpf_lsm_hooks, prog->aux->attach_btf_id)) {
bpf_log(vlog, "attach_btf_id %u points to wrong type name %s\n",
prog->aux->attach_btf_id, prog->aux->attach_func_name);
return -EINVAL;
}
return 0;
}
/* Mask for all the currently supported BPRM option flags */
#define BPF_F_BRPM_OPTS_MASK BPF_F_BPRM_SECUREEXEC
BPF_CALL_2(bpf_bprm_opts_set, struct linux_binprm *, bprm, u64, flags)
{
if (flags & ~BPF_F_BRPM_OPTS_MASK)
return -EINVAL;
bprm->secureexec = (flags & BPF_F_BPRM_SECUREEXEC);
return 0;
}
BTF_ID_LIST_SINGLE(bpf_bprm_opts_set_btf_ids, struct, linux_binprm)
static const struct bpf_func_proto bpf_bprm_opts_set_proto = {
.func = bpf_bprm_opts_set,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_BTF_ID,
.arg1_btf_id = &bpf_bprm_opts_set_btf_ids[0],
.arg2_type = ARG_ANYTHING,
};
BPF_CALL_3(bpf_ima_inode_hash, struct inode *, inode, void *, dst, u32, size)
{
return ima_inode_hash(inode, dst, size);
}
static bool bpf_ima_inode_hash_allowed(const struct bpf_prog *prog)
{
return bpf_lsm_is_sleepable_hook(prog->aux->attach_btf_id);
}
BTF_ID_LIST_SINGLE(bpf_ima_inode_hash_btf_ids, struct, inode)
static const struct bpf_func_proto bpf_ima_inode_hash_proto = {
.func = bpf_ima_inode_hash,
.gpl_only = false,
.might_sleep = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_BTF_ID,
.arg1_btf_id = &bpf_ima_inode_hash_btf_ids[0],
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE,
.allowed = bpf_ima_inode_hash_allowed,
};
BPF_CALL_3(bpf_ima_file_hash, struct file *, file, void *, dst, u32, size)
{
return ima_file_hash(file, dst, size);
}
BTF_ID_LIST_SINGLE(bpf_ima_file_hash_btf_ids, struct, file)
static const struct bpf_func_proto bpf_ima_file_hash_proto = {
.func = bpf_ima_file_hash,
.gpl_only = false,
.might_sleep = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_BTF_ID,
.arg1_btf_id = &bpf_ima_file_hash_btf_ids[0],
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE,
.allowed = bpf_ima_inode_hash_allowed,
};
BPF_CALL_1(bpf_get_attach_cookie, void *, ctx)
{
struct bpf_trace_run_ctx *run_ctx;
run_ctx = container_of(current->bpf_ctx, struct bpf_trace_run_ctx, run_ctx);
return run_ctx->bpf_cookie;
}
static const struct bpf_func_proto bpf_get_attach_cookie_proto = {
.func = bpf_get_attach_cookie,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
};
static const struct bpf_func_proto *
bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
const struct bpf_func_proto *func_proto;
if (prog->expected_attach_type == BPF_LSM_CGROUP) {
func_proto = cgroup_common_func_proto(func_id, prog);
if (func_proto)
return func_proto;
}
switch (func_id) {
case BPF_FUNC_inode_storage_get:
return &bpf_inode_storage_get_proto;
case BPF_FUNC_inode_storage_delete:
return &bpf_inode_storage_delete_proto;
#ifdef CONFIG_NET
case BPF_FUNC_sk_storage_get:
return &bpf_sk_storage_get_proto;
case BPF_FUNC_sk_storage_delete:
return &bpf_sk_storage_delete_proto;
#endif /* CONFIG_NET */
case BPF_FUNC_spin_lock:
return &bpf_spin_lock_proto;
case BPF_FUNC_spin_unlock:
return &bpf_spin_unlock_proto;
case BPF_FUNC_bprm_opts_set:
return &bpf_bprm_opts_set_proto;
case BPF_FUNC_ima_inode_hash:
return &bpf_ima_inode_hash_proto;
case BPF_FUNC_ima_file_hash:
return &bpf_ima_file_hash_proto;
case BPF_FUNC_get_attach_cookie:
return bpf_prog_has_trampoline(prog) ? &bpf_get_attach_cookie_proto : NULL;
#ifdef CONFIG_NET
case BPF_FUNC_setsockopt:
if (prog->expected_attach_type != BPF_LSM_CGROUP)
return NULL;
if (btf_id_set_contains(&bpf_lsm_locked_sockopt_hooks,
prog->aux->attach_btf_id))
return &bpf_sk_setsockopt_proto;
if (btf_id_set_contains(&bpf_lsm_unlocked_sockopt_hooks,
prog->aux->attach_btf_id))
return &bpf_unlocked_sk_setsockopt_proto;
return NULL;
case BPF_FUNC_getsockopt:
if (prog->expected_attach_type != BPF_LSM_CGROUP)
return NULL;
if (btf_id_set_contains(&bpf_lsm_locked_sockopt_hooks,
prog->aux->attach_btf_id))
return &bpf_sk_getsockopt_proto;
if (btf_id_set_contains(&bpf_lsm_unlocked_sockopt_hooks,
prog->aux->attach_btf_id))
return &bpf_unlocked_sk_getsockopt_proto;
return NULL;
#endif
default:
return tracing_prog_func_proto(func_id, prog);
}
}
/* The set of hooks which are called without pagefaults disabled and are allowed
* to "sleep" and thus can be used for sleepable BPF programs.
*/
BTF_SET_START(sleepable_lsm_hooks)
BTF_ID(func, bpf_lsm_bpf)
BTF_ID(func, bpf_lsm_bpf_map)
BTF_ID(func, bpf_lsm_bpf_map_alloc_security)
BTF_ID(func, bpf_lsm_bpf_map_free_security)
BTF_ID(func, bpf_lsm_bpf_prog)
BTF_ID(func, bpf_lsm_bprm_check_security)
BTF_ID(func, bpf_lsm_bprm_committed_creds)
BTF_ID(func, bpf_lsm_bprm_committing_creds)
BTF_ID(func, bpf_lsm_bprm_creds_for_exec)
BTF_ID(func, bpf_lsm_bprm_creds_from_file)
BTF_ID(func, bpf_lsm_capget)
BTF_ID(func, bpf_lsm_capset)
BTF_ID(func, bpf_lsm_cred_prepare)
BTF_ID(func, bpf_lsm_file_ioctl)
BTF_ID(func, bpf_lsm_file_lock)
BTF_ID(func, bpf_lsm_file_open)
BTF_ID(func, bpf_lsm_file_receive)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_inet_conn_established)
#endif /* CONFIG_SECURITY_NETWORK */
BTF_ID(func, bpf_lsm_inode_create)
BTF_ID(func, bpf_lsm_inode_free_security)
BTF_ID(func, bpf_lsm_inode_getattr)
BTF_ID(func, bpf_lsm_inode_getxattr)
BTF_ID(func, bpf_lsm_inode_mknod)
BTF_ID(func, bpf_lsm_inode_need_killpriv)
BTF_ID(func, bpf_lsm_inode_post_setxattr)
BTF_ID(func, bpf_lsm_inode_readlink)
BTF_ID(func, bpf_lsm_inode_rename)
BTF_ID(func, bpf_lsm_inode_rmdir)
BTF_ID(func, bpf_lsm_inode_setattr)
BTF_ID(func, bpf_lsm_inode_setxattr)
BTF_ID(func, bpf_lsm_inode_symlink)
BTF_ID(func, bpf_lsm_inode_unlink)
BTF_ID(func, bpf_lsm_kernel_module_request)
BTF_ID(func, bpf_lsm_kernel_read_file)
BTF_ID(func, bpf_lsm_kernfs_init_security)
#ifdef CONFIG_KEYS
BTF_ID(func, bpf_lsm_key_free)
#endif /* CONFIG_KEYS */
BTF_ID(func, bpf_lsm_mmap_file)
BTF_ID(func, bpf_lsm_netlink_send)
BTF_ID(func, bpf_lsm_path_notify)
BTF_ID(func, bpf_lsm_release_secctx)
BTF_ID(func, bpf_lsm_sb_alloc_security)
BTF_ID(func, bpf_lsm_sb_eat_lsm_opts)
BTF_ID(func, bpf_lsm_sb_kern_mount)
BTF_ID(func, bpf_lsm_sb_mount)
BTF_ID(func, bpf_lsm_sb_remount)
BTF_ID(func, bpf_lsm_sb_set_mnt_opts)
BTF_ID(func, bpf_lsm_sb_show_options)
BTF_ID(func, bpf_lsm_sb_statfs)
BTF_ID(func, bpf_lsm_sb_umount)
BTF_ID(func, bpf_lsm_settime)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_socket_accept)
BTF_ID(func, bpf_lsm_socket_bind)
BTF_ID(func, bpf_lsm_socket_connect)
BTF_ID(func, bpf_lsm_socket_create)
BTF_ID(func, bpf_lsm_socket_getpeername)
BTF_ID(func, bpf_lsm_socket_getpeersec_dgram)
BTF_ID(func, bpf_lsm_socket_getsockname)
BTF_ID(func, bpf_lsm_socket_getsockopt)
BTF_ID(func, bpf_lsm_socket_listen)
BTF_ID(func, bpf_lsm_socket_post_create)
BTF_ID(func, bpf_lsm_socket_recvmsg)
BTF_ID(func, bpf_lsm_socket_sendmsg)
BTF_ID(func, bpf_lsm_socket_shutdown)
BTF_ID(func, bpf_lsm_socket_socketpair)
#endif /* CONFIG_SECURITY_NETWORK */
BTF_ID(func, bpf_lsm_syslog)
BTF_ID(func, bpf_lsm_task_alloc)
BTF_ID(func, bpf_lsm_current_getsecid_subj)
BTF_ID(func, bpf_lsm_task_getsecid_obj)
BTF_ID(func, bpf_lsm_task_prctl)
BTF_ID(func, bpf_lsm_task_setscheduler)
BTF_ID(func, bpf_lsm_task_to_inode)
BTF_ID(func, bpf_lsm_userns_create)
BTF_SET_END(sleepable_lsm_hooks)
BTF_SET_START(untrusted_lsm_hooks)
BTF_ID(func, bpf_lsm_bpf_map_free_security)
BTF_ID(func, bpf_lsm_bpf_prog_alloc_security)
BTF_ID(func, bpf_lsm_bpf_prog_free_security)
BTF_ID(func, bpf_lsm_file_alloc_security)
BTF_ID(func, bpf_lsm_file_free_security)
#ifdef CONFIG_SECURITY_NETWORK
BTF_ID(func, bpf_lsm_sk_alloc_security)
BTF_ID(func, bpf_lsm_sk_free_security)
#endif /* CONFIG_SECURITY_NETWORK */
BTF_ID(func, bpf_lsm_task_free)
BTF_SET_END(untrusted_lsm_hooks)
bool bpf_lsm_is_sleepable_hook(u32 btf_id)
{
return btf_id_set_contains(&sleepable_lsm_hooks, btf_id);
}
bool bpf_lsm_is_trusted(const struct bpf_prog *prog)
{
return !btf_id_set_contains(&untrusted_lsm_hooks, prog->aux->attach_btf_id);
}
const struct bpf_prog_ops lsm_prog_ops = {
};
const struct bpf_verifier_ops lsm_verifier_ops = {
.get_func_proto = bpf_lsm_func_proto,
.is_valid_access = btf_ctx_access,
};
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