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);