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ovl: automatically enable redirect_dir on metacopy=on

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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: Daniel Walsh <dwalsh@redhat.com>
Fixes: d5791044d2 ("ovl: Provide a mount option metacopy=on/off...")
Cc: <stable@vger.kernel.org> # v4.19
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2018-11-01 21:31:39 +01:00
parent 5e12758086
commit d47748e5ae
2 changed files with 35 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/filesystems/overlayfs.txt
View File

@ -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
--------------------------

36
fs/overlayfs/super.c
View File

@ -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");
config->metacopy = false;
/*
* 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;