runtime tested on ar71xx with kernel 3.18.11
this paritially fixes #19564
Signed-off-by: Bastian Bittorf <bitt...@bluebottle.com>
---
...unt-read-only-if-workdir-can-t-be-created.patch | 114 ++++++++++++++++++++
1 file changed, 114 insertions(+)
create mode 100644
target/linux/ar71xx/patches-3.18/910-overlayfs-mount-read-only-if-workdir-can-t-be-created.patch
diff --git
a/target/linux/ar71xx/patches-3.18/910-overlayfs-mount-read-only-if-workdir-can-t-be-created.patch
b/target/linux/ar71xx/patches-3.18/910-overlayfs-mount-read-only-if-workdir-can-t-be-created.patch
new file mode 100644
index 0000000..e563398
--- /dev/null
+++
b/target/linux/ar71xx/patches-3.18/910-overlayfs-mount-read-only-if-workdir-can-t-be-created.patch
@@ -0,0 +1,114 @@
+From cc6f67bcafcb6bbbb2d1be1603dcd95125a52800 Mon Sep 17 00:00:00 2001
+From: Miklos Szeredi <mszer...@suse.cz>
+Date: Tue, 19 May 2015 14:30:12 +0200
+Subject: [PATCH] ovl: mount read-only if workdir can't be created
+
+OpenWRT folks reported that overlayfs fails to mount if upper fs is full,
+because workdir can't be created. Wordir creation can fail for various
+other reasons too.
+
+There's no reason that the mount itself should fail, overlayfs can work
+fine without a workdir, as long as the overlay isn't modified.
+
+So mount it read-only and don't allow remounting read-write.
+
+Add a couple of WARN_ON()s for the impossible case of workdir being used
+despite being read-only.
+
+Reported-by: Bastian Bittorf <bitt...@bluebottle.com>
+Signed-off-by: Miklos Szeredi <mszer...@suse.cz>
+Cc: <sta...@vger.kernel.org> # v3.18+
+Signed-off-by: Bastian Bittorf <bitt...@bluebottle.com>
+
+---
+ fs/overlayfs/copy_up.c | 3 +++
+ fs/overlayfs/dir.c | 9 +++++++++
+ fs/overlayfs/super.c | 10 +++++-----
+ 3 files changed, 17 insertions(+), 5 deletions(-)
+
+diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
+index 24f6404..84d693d 100644
+--- a/fs/overlayfs/copy_up.c
++++ b/fs/overlayfs/copy_up.c
+@@ -299,6 +299,9 @@ int ovl_copy_up_one(struct dentry *parent, struct dentry
*dentry,
+ struct cred *override_cred;
+ char *link = NULL;
+
++ if (WARN_ON(!workdir))
++ return -EROFS;
++
+ ovl_path_upper(parent, &parentpath);
+ upperdir = parentpath.dentry;
+
+diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
+index 2578a0c..692ceda 100644
+--- a/fs/overlayfs/dir.c
++++ b/fs/overlayfs/dir.c
+@@ -222,6 +222,9 @@ static struct dentry *ovl_clear_empty(struct dentry
*dentry,
+ struct kstat stat;
+ int err;
+
++ if (WARN_ON(!workdir))
++ return ERR_PTR(-EROFS);
++
+ err = ovl_lock_rename_workdir(workdir, upperdir);
+ if (err)
+ goto out;
+@@ -322,6 +325,9 @@ static int ovl_create_over_whiteout(struct dentry *dentry,
struct inode *inode,
+ struct dentry *newdentry;
+ int err;
+
++ if (WARN_ON(!workdir))
++ return -EROFS;
++
+ err = ovl_lock_rename_workdir(workdir, upperdir);
+ if (err)
+ goto out;
+@@ -506,6 +512,9 @@ static int ovl_remove_and_whiteout(struct dentry *dentry,
bool is_dir)
+ struct dentry *opaquedir = NULL;
+ int err;
+
++ if (WARN_ON(!workdir))
++ return -EROFS;
++
+ if (is_dir) {
+ if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
+ opaquedir = ovl_check_empty_and_clear(dentry);
+diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
+index 5f0d199..bf8537c 100644
+--- a/fs/overlayfs/super.c
++++ b/fs/overlayfs/super.c
+@@ -529,7 +529,7 @@ static int ovl_remount(struct super_block *sb, int *flags,
char *data)
+ {
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+- if (!(*flags & MS_RDONLY) && !ufs->upper_mnt)
++ if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
+ return -EROFS;
+
+ return 0;
+@@ -925,9 +925,10 @@ static int ovl_fill_super(struct super_block *sb, void
*data, int silent)
+ ufs->workdir = ovl_workdir_create(ufs->upper_mnt,
workpath.dentry);
+ err = PTR_ERR(ufs->workdir);
+ if (IS_ERR(ufs->workdir)) {
+- pr_err("overlayfs: failed to create directory %s/%s\n",
+- ufs->config.workdir, OVL_WORKDIR_NAME);
+- goto out_put_upper_mnt;
++ pr_warn("overlayfs: failed to create directory %s/%s
(errno: %i); mounting read-only\n",
++ ufs->config.workdir, OVL_WORKDIR_NAME, -err);
++ sb->s_flags |= MS_RDONLY;
++ ufs->workdir = NULL;
+ }
+ }
+
+@@ -997,7 +998,6 @@ out_put_lower_mnt:
+ kfree(ufs->lower_mnt);
+ out_put_workdir:
+ dput(ufs->workdir);
+-out_put_upper_mnt:
+ mntput(ufs->upper_mnt);
+ out_put_lowerpath:
+ for (i = 0; i < numlower; i++)
+--
+1.7.10.4
+
--
1.7.10.4
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