bpf-lsm: Make bpf_lsm_kernel_read_file() as sleepable

Make bpf_lsm_kernel_read_file() as sleepable, so that bpf_ima_inode_hash()
or bpf_ima_file_hash() can be called inside the implementation of this
hook.
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220302111404.193900-8-roberto.sassu@huawei.com

kernel/bpf/bpf_lsm.c

@@ -187,6 +187,7 @@ 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