bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/fs/ext2/xattr_trusted.c b/fs/ext2/xattr_trusted.c
new file mode 100644
index 000000000..995f93122
--- /dev/null
+++ b/fs/ext2/xattr_trusted.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext2/xattr_trusted.c
+ * Handler for trusted extended attributes.
+ *
+ * Copyright (C) 2003 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
+ */
+
+#include "ext2.h"
+#include "xattr.h"
+
+static bool
+ext2_xattr_trusted_list(struct dentry *dentry)
+{
+	return capable(CAP_SYS_ADMIN);
+}
+
+static int
+ext2_xattr_trusted_get(const struct xattr_handler *handler,
+		       struct dentry *unused, struct inode *inode,
+		       const char *name, void *buffer, size_t size)
+{
+	return ext2_xattr_get(inode, EXT2_XATTR_INDEX_TRUSTED, name,
+			      buffer, size);
+}
+
+static int
+ext2_xattr_trusted_set(const struct xattr_handler *handler,
+		       struct mnt_idmap *idmap,
+		       struct dentry *unused, struct inode *inode,
+		       const char *name, const void *value,
+		       size_t size, int flags)
+{
+	return ext2_xattr_set(inode, EXT2_XATTR_INDEX_TRUSTED, name,
+			      value, size, flags);
+}
+
+const struct xattr_handler ext2_xattr_trusted_handler = {
+	.prefix	= XATTR_TRUSTED_PREFIX,
+	.list	= ext2_xattr_trusted_list,
+	.get	= ext2_xattr_trusted_get,
+	.set	= ext2_xattr_trusted_set,
+};