Commit 1a17e5b5 authored by Kees Cook's avatar Kees Cook
Browse files

LoadPin: Ignore the "contents" argument of the LSM hooks 



LoadPin only enforces the read-only origin of kernel file reads. Whether
or not it was a partial read isn't important. Remove the overly
conservative checks so that things like partial firmware reads will
succeed (i.e. reading a firmware header).

Fixes: 2039bda1 ("LSM: Add "contents" flag to kernel_read_file hook")
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-security-module@vger.kernel.org
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarSerge Hallyn <serge@hallyn.com>
Tested-by: default avatarPing-Ke Shih <pkshih@realtek.com>
Link: https://lore.kernel.org/r/20221209195453.never.494-kees@kernel.org
parent d272e01f

security/loadpin/loadpin.c

+18 −12
Original line number Diff line number Diff line
@@ -122,21 +122,11 @@ static void loadpin_sb_free_security(struct super_block *mnt_sb) 
	}

}



static int loadpin_read_file(struct file *file, enum kernel_read_file_id id,

			     bool contents)

static int loadpin_check(struct file *file, enum kernel_read_file_id id)

{

	struct super_block *load_root;

	const char *origin = kernel_read_file_id_str(id);



	/*

	 * If we will not know that we'll be seeing the full contents

	 * then we cannot trust a load will be complete and unchanged

	 * off disk. Treat all contents=false hooks as if there were

	 * no associated file struct.

	 */

	if (!contents)

		file = NULL;



	/* If the file id is excluded, ignore the pinning. */

	if ((unsigned int)id < ARRAY_SIZE(ignore_read_file_id) &&

	    ignore_read_file_id[id]) {
@@ -192,9 +182,25 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id, 
	return 0;

}



static int loadpin_read_file(struct file *file, enum kernel_read_file_id id,

			     bool contents)

{

	/*

	 * LoadPin only cares about the _origin_ of a file, not its

	 * contents, so we can ignore the "are full contents available"

	 * argument here.

	 */

	return loadpin_check(file, id);

}



static int loadpin_load_data(enum kernel_load_data_id id, bool contents)

{

	return loadpin_read_file(NULL, (enum kernel_read_file_id) id, contents);

	/*

	 * LoadPin only cares about the _origin_ of a file, not its

	 * contents, so a NULL file is passed, and we can ignore the

	 * state of "contents".

	 */

	return loadpin_check(NULL, (enum kernel_read_file_id) id);

}



static struct security_hook_list loadpin_hooks[] __lsm_ro_after_init = {