From bead55ef775f6e25a8d286c0d47030580f577bec Mon Sep 17 00:00:00 2001 From: hujianyang Date: Thu, 15 Jan 2015 13:17:36 +0800 Subject: [PATCH 1/3] ovl: print error message for invalid mount options Overlayfs should print an error message if an incorrect mount option is caught like other filesystems. After this patch, improper option input could be clearly known. Reported-by: Fabian Sturm Signed-off-by: hujianyang Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index b90952f528b1..ab3c8cb8e52d 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -615,6 +615,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) break; default: + pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p); return -EINVAL; } } From 6be4506e34cf6075a1307b646e0a6c46c1c9010d Mon Sep 17 00:00:00 2001 From: hujianyang Date: Thu, 15 Jan 2015 13:19:21 +0800 Subject: [PATCH 2/3] ovl: check lowerdir amount for non-upper mount Recently multi-lower layer mount support allow upperdir and workdir to be omitted, then cause overlayfs can be mount with only one lowerdir directory. This action make no sense and have potential risk. This patch check the total number of lower directories to prevent mounting overlayfs with only one directory. Also, an error message is added to indicate lower directories exceed OVL_MAX_STACK limit. Signed-off-by: hujianyang Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index ab3c8cb8e52d..edbb3ebcdaad 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -870,8 +870,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) err = -EINVAL; stacklen = ovl_split_lowerdirs(lowertmp); - if (stacklen > OVL_MAX_STACK) + if (stacklen > OVL_MAX_STACK) { + pr_err("overlayfs: too many lower directries, limit is %d\n", + OVL_MAX_STACK); goto out_free_lowertmp; + } else if (!ufs->config.upperdir && stacklen == 1) { + pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); + goto out_free_lowertmp; + } stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL); if (!stack) From 71cbad7e694ee81233b3be3a38b81c3d5872cc6f Mon Sep 17 00:00:00 2001 From: hujianyang Date: Thu, 15 Jan 2015 13:20:57 +0800 Subject: [PATCH 3/3] ovl: upper fs should not be R/O After importing multi-lower layer support, users could mount a r/o partition as the left most lowerdir instead of using it as upperdir. And a r/o upperdir may cause an error like overlayfs: failed to create directory ./workdir/work during mount. This patch check the *s_flags* of upper fs and return an error if it is a r/o partition. The checking of *upper_mnt->mnt_sb->s_flags* can be removed now. This patch also remove /* FIXME: workdir is not needed for a R/O mount */ from ovl_fill_super() because: 1) for upper fs r/o case Setting a r/o partition as upper is prevented, no need to care about workdir in this case. 2) for "mount overlay -o ro" with a r/w upper fs case Users could remount overlayfs to r/w in this case, so workdir should not be omitted. Signed-off-by: hujianyang Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index edbb3ebcdaad..5f0d1993e6e3 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -529,8 +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 || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))) + if (!(*flags & MS_RDONLY) && !ufs->upper_mnt) return -EROFS; return 0; @@ -619,6 +618,15 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) return -EINVAL; } } + + /* Workdir is useless in non-upper mount */ + if (!config->upperdir && config->workdir) { + pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n", + config->workdir); + kfree(config->workdir); + config->workdir = NULL; + } + return 0; } @@ -838,7 +846,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) sb->s_stack_depth = 0; if (ufs->config.upperdir) { - /* FIXME: workdir is not needed for a R/O mount */ if (!ufs->config.workdir) { pr_err("overlayfs: missing 'workdir'\n"); goto out_free_config; @@ -848,6 +855,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) if (err) goto out_free_config; + /* Upper fs should not be r/o */ + if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) { + pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n"); + err = -EINVAL; + goto out_put_upperpath; + } + err = ovl_mount_dir(ufs->config.workdir, &workpath); if (err) goto out_put_upperpath; @@ -939,8 +953,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) ufs->numlower++; } - /* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */ - if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)) + /* If the upper fs is nonexistent, we mark overlayfs r/o too */ + if (!ufs->upper_mnt) sb->s_flags |= MS_RDONLY; sb->s_d_op = &ovl_dentry_operations;