4.19-stable review patch. If anyone has any objections, please let me know.
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From: Miklos Szeredi mszeredi@redhat.com
commit d47748e5ae5af6572e520cc9767bbe70c22ea498 upstream.
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: d5791044d2e5 ("ovl: Provide a mount option metacopy=on/off...") Cc: stable@vger.kernel.org # v4.19 Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- Documentation/filesystems/overlayfs.txt | 6 +++++ fs/overlayfs/super.c | 36 +++++++++++++++++++++++++------- 2 files changed, 35 insertions(+), 7 deletions(-)
--- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -286,6 +286,12 @@ pointed by REDIRECT. This should not be "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 --------------------------
--- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -472,6 +472,7 @@ static int ovl_parse_opt(char *opt, stru { 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, stru 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, stru
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, stru 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;