bpf: Move bpf_get_file_xattr to fs/bpf_fs_kfuncs.c

We are putting all fs kfuncs in fs/bpf_fs_kfuncs.c. Move existing
bpf_get_file_xattr to it.

Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240806230904.71194-2-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c
index 1e6e08667758..b13d00f7ad2b 100644
--- a/fs/bpf_fs_kfuncs.c
+++ b/fs/bpf_fs_kfuncs.c
@@ -8,6 +8,7 @@
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/mm.h>
+#include <linux/xattr.h>
 
 __bpf_kfunc_start_defs();
 
@@ -92,6 +93,42 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz)
 	return len;
 }
 
+/**
+ * bpf_get_file_xattr - get xattr of a file
+ * @file: file to get xattr from
+ * @name__str: name of the xattr
+ * @value_p: output buffer of the xattr value
+ *
+ * Get xattr *name__str* of *file* and store the output in *value_ptr*.
+ *
+ * For security reasons, only *name__str* with prefix "user." is allowed.
+ *
+ * Return: 0 on success, a negative value on error.
+ */
+__bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str,
+				   struct bpf_dynptr *value_p)
+{
+	struct bpf_dynptr_kern *value_ptr = (struct bpf_dynptr_kern *)value_p;
+	struct dentry *dentry;
+	u32 value_len;
+	void *value;
+	int ret;
+
+	if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
+		return -EPERM;
+
+	value_len = __bpf_dynptr_size(value_ptr);
+	value = __bpf_dynptr_data_rw(value_ptr, value_len);
+	if (!value)
+		return -EINVAL;
+
+	dentry = file_dentry(file);
+	ret = inode_permission(&nop_mnt_idmap, dentry->d_inode, MAY_READ);
+	if (ret)
+		return ret;
+	return __vfs_getxattr(dentry, dentry->d_inode, name__str, value, value_len);
+}
+
 __bpf_kfunc_end_defs();
 
 BTF_KFUNCS_START(bpf_fs_kfunc_set_ids)
@@ -99,6 +136,7 @@ BTF_ID_FLAGS(func, bpf_get_task_exe_file,
 	     KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_put_file, KF_RELEASE)
 BTF_ID_FLAGS(func, bpf_path_d_path, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEEPABLE | KF_TRUSTED_ARGS)
 BTF_KFUNCS_END(bpf_fs_kfunc_set_ids)
 
 static int bpf_fs_kfuncs_filter(const struct bpf_prog *prog, u32 kfunc_id)