[PATCH v5 bpf-next 4/5] bpf: Add a bpf_getxattr kfunc
From: KP Singh <kpsingh@kernel.org>
Date: 2022-06-28 16:30:20
Also in:
bpf, linux-fsdevel
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [security & lsm] (security audit and enforcement using bpf), bpf [tracing], the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, KP Singh, Matt Bobrowski, Song Liu, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
LSMs like SELinux store security state in xattrs. bpf_getxattr enables BPF LSM to implement similar functionality. In combination with bpf_local_storage, xattrs can be used to develop more complex security policies. This kfunc wraps around __vfs_getxattr which can sleep and is, therefore, limited to sleepable programs using the newly added sleepable_set for kfuncs. Signed-off-by: KP Singh <kpsingh@kernel.org> --- kernel/trace/bpf_trace.c | 42 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 4be976cf7d63..87496d57b099 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c@@ -20,6 +20,7 @@ #include <linux/fprobe.h> #include <linux/bsearch.h> #include <linux/sort.h> +#include <linux/xattr.h> #include <net/bpf_sk_storage.h>
@@ -1181,6 +1182,47 @@ static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = { .arg1_type = ARG_PTR_TO_CTX, }; +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "kfuncs that are used in tracing/LSM BPF programs"); + +ssize_t bpf_getxattr(struct dentry *dentry, struct inode *inode, + const char *name, void *value, int value__sz) +{ + return __vfs_getxattr(dentry, inode, name, value, value__sz); +} + +__diag_pop(); + +BTF_SET_START(bpf_trace_kfunc_ids) +BTF_ID(func, bpf_getxattr) +BTF_SET_END(bpf_trace_kfunc_ids) + +BTF_SET_START(bpf_trace_sleepable_kfunc_ids) +BTF_ID(func, bpf_getxattr) +BTF_SET_END(bpf_trace_sleepable_kfunc_ids) + +static const struct btf_kfunc_id_set bpf_trace_kfunc_set = { + .owner = THIS_MODULE, + .check_set = &bpf_trace_kfunc_ids, + .sleepable_set = &bpf_trace_sleepable_kfunc_ids, +}; + +static int __init bpf_trace_kfunc_init(void) +{ + int ret; + + ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, + &bpf_trace_kfunc_set); + if (!ret) + return ret; + + return register_btf_kfunc_id_set(BPF_PROG_TYPE_LSM, + &bpf_trace_kfunc_set); + +} +late_initcall(bpf_trace_kfunc_init); + static const struct bpf_func_proto * bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) {
--
2.37.0.rc0.161.g10f37bed90-goog