Commit d47748e5 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

ovl: automatically enable redirect_dir on metacopy=on 



Current behavior is to automatically disable metacopy if redirect_dir is
not enabled and proceed with the mount.

If "metacopy=on" mount option was given, then this behavior can confuse the
user: no mount failure, yet metacopy is disabled.

This patch makes metacopy=on imply redirect_dir=on.

The converse is also true: turning off full redirect with redirect_dir=
{off|follow|nofollow} will disable metacopy.

If both metacopy=on and redirect_dir={off|follow|nofollow} is specified,
then mount will fail, since there's no way to correctly resolve the
conflict.

Reported-by: default avatarDaniel Walsh <dwalsh@redhat.com>
Fixes: d5791044 ("ovl: Provide a mount option metacopy=on/off...")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 5e127580

Documentation/filesystems/overlayfs.txt

+6 −0
Original line number Diff line number Diff line
@@ -286,6 +286,12 @@ pointed by REDIRECT. This should not be possible on local system as setting 
"trusted." xattrs will require CAP_SYS_ADMIN. But it should be possible

for untrusted layers like from a pen drive.



Note: redirect_dir={off|nofollow|follow(*)} conflicts with metacopy=on, and

results in an error.



(*) redirect_dir=follow only conflicts with metacopy=on if upperdir=... is

given.



Sharing and copying layers

--------------------------

fs/overlayfs/super.c

+29 −7
Original line number Diff line number Diff line
@@ -472,6 +472,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
{

	char *p;

	int err;

	bool metacopy_opt = false, redirect_opt = false;



	config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);

	if (!config->redirect_mode)
@@ -516,6 +517,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
			config->redirect_mode = match_strdup(&args[0]);

			if (!config->redirect_mode)

				return -ENOMEM;

			redirect_opt = true;

			break;



		case OPT_INDEX_ON:
@@ -548,6 +550,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 


		case OPT_METACOPY_ON:

			config->metacopy = true;

			metacopy_opt = true;

			break;



		case OPT_METACOPY_OFF:
@@ -572,13 +575,32 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
	if (err)

		return err;



	/* metacopy feature with upper requires redirect_dir=on */

	if (config->upperdir && config->metacopy && !config->redirect_dir) {

		pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=on\", falling back to metacopy=off.\n");

		config->metacopy = false;

	} else if (config->metacopy && !config->redirect_follow) {

		pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=follow\" on non-upper mount, falling back to metacopy=off.\n");

	/*

	 * This is to make the logic below simpler.  It doesn't make any other

	 * difference, since config->redirect_dir is only used for upper.

	 */

	if (!config->upperdir && config->redirect_follow)

		config->redirect_dir = true;



	/* Resolve metacopy -> redirect_dir dependency */

	if (config->metacopy && !config->redirect_dir) {

		if (metacopy_opt && redirect_opt) {

			pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",

			       config->redirect_mode);

			return -EINVAL;

		}

		if (redirect_opt) {

			/*

			 * There was an explicit redirect_dir=... that resulted

			 * in this conflict.

			 */

			pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",

				config->redirect_mode);

			config->metacopy = false;

		} else {

			/* Automatically enable redirect otherwise. */

			config->redirect_follow = config->redirect_dir = true;

		}

	}



	return 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE