Commit 423f1610 authored by KP Singh's avatar KP Singh Committed by Daniel Borkmann
Browse files

bpf: Augment the set of sleepable LSM hooks 



Update the set of sleepable hooks with the ones that do not trigger
a warning with might_fault() when exercised with the correct kernel
config options enabled, i.e.

	DEBUG_ATOMIC_SLEEP=y
	LOCKDEP=y
	PROVE_LOCKING=y

This means that a sleepable LSM eBPF program can be attached to these
LSM hooks. A new helper method bpf_lsm_is_sleepable_hook is added and
the set is maintained locally in bpf_lsm.c

Signed-off-by: default avatarKP Singh <kpsingh@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201113005930.541956-2-kpsingh@chromium.org
parent 904709f6

include/linux/bpf_lsm.h

+7 −0
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ extern struct lsm_blob_sizes bpf_lsm_blob_sizes; 
int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,

			const struct bpf_prog *prog);



bool bpf_lsm_is_sleepable_hook(u32 btf_id);



static inline struct bpf_storage_blob *bpf_inode(

	const struct inode *inode)

{
@@ -54,6 +56,11 @@ void bpf_task_storage_free(struct task_struct *task); 


#else /* !CONFIG_BPF_LSM */



static inline bool bpf_lsm_is_sleepable_hook(u32 btf_id)

{

	return false;

}



static inline int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,

				      const struct bpf_prog *prog)

{

kernel/bpf/bpf_lsm.c

+81 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/bpf_verifier.h>

#include <net/bpf_sk_storage.h>

#include <linux/bpf_local_storage.h>

#include <linux/btf_ids.h>



/* For every LSM hook that allows attachment of BPF programs, declare a nop

 * function where a BPF program can be attached.
@@ -72,6 +73,86 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) 
	}

}



/* The set of hooks which are called without pagefaults disabled and are allowed

 * to "sleep" and thus can be used for sleeable 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)

BTF_ID(func, bpf_lsm_inet_conn_established)

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_kernfs_init_security)

BTF_ID(func, bpf_lsm_key_free)

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)

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)

BTF_ID(func, bpf_lsm_syslog)

BTF_ID(func, bpf_lsm_task_alloc)

BTF_ID(func, bpf_lsm_task_getsecid)

BTF_ID(func, bpf_lsm_task_prctl)

BTF_ID(func, bpf_lsm_task_setscheduler)

BTF_ID(func, bpf_lsm_task_to_inode)

BTF_SET_END(sleepable_lsm_hooks)



bool bpf_lsm_is_sleepable_hook(u32 btf_id)

{

	return btf_id_set_contains(&sleepable_lsm_hooks, btf_id);

}



const struct bpf_prog_ops lsm_prog_ops = {

};

kernel/bpf/verifier.c

+1 −15
Original line number Diff line number Diff line
@@ -11562,20 +11562,6 @@ static int check_attach_modify_return(unsigned long addr, const char *func_name) 
	return -EINVAL;

}



/* non exhaustive list of sleepable bpf_lsm_*() functions */

BTF_SET_START(btf_sleepable_lsm_hooks)

#ifdef CONFIG_BPF_LSM

BTF_ID(func, bpf_lsm_bprm_committed_creds)

#else

BTF_ID_UNUSED

#endif

BTF_SET_END(btf_sleepable_lsm_hooks)



static int check_sleepable_lsm_hook(u32 btf_id)

{

	return btf_id_set_contains(&btf_sleepable_lsm_hooks, btf_id);

}



/* list of non-sleepable functions that are otherwise on

 * ALLOW_ERROR_INJECTION list

 */
@@ -11797,7 +11783,7 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, 
				/* LSM progs check that they are attached to bpf_lsm_*() funcs.

				 * Only some of them are sleepable.

				 */

				if (check_sleepable_lsm_hook(btf_id))

				if (bpf_lsm_is_sleepable_hook(btf_id))

					ret = 0;

				break;

			default:

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