kernel.git/fs/overlayfs/params.c, branch linux-6.10.y

ovl: fail if trusted xattrs are needed but caller lacks permission

2024-10-10T10:00:47Z

commit 6c4a5f96450415735c31ed70ff354f0ee5cbf67b upstream. Some overlayfs features require permission to read/write trusted.* xattrs. These include redirect_dir, verity, metacopy, and data-only layers. This patch adds additional validations at mount time to stop overlays from mounting in certain cases where the resulting mount would not function according to the user's expectations because they lack permission to access trusted.* xattrs (for example, not global root.) Similar checks in ovl_make_workdir() that disable features instead of failing are still relevant and used in cases where the resulting mount can still work "reasonably well." Generally, if the feature was enabled through kernel config or module option, any mount that worked before will still work the same; this applies to redirect_dir and metacopy. The user must explicitly request these features in order to generate a mount failure. Verity and data-only layers on the other hand must be explictly requested and have no "reasonable" disabled or degraded alternative, so mounts attempting either always fail. "lower data-only dirs require metacopy support" moved down in case userxattr is set, which disables metacopy. Cc: stable@vger.kernel.org # v6.6+ Signed-off-by: Mike Baynton Signed-off-by: Amir Goldstein Signed-off-by: Greg Kroah-Hartman

fs_parser: move fsparam_string_empty() helper into header

2024-03-26T08:01:18Z

Since both ext4 and overlayfs define the same macro to specify string parameters that may allow empty values, define it in an header file so that this helper can be shared. Signed-off-by: Luis Henriques (SUSE) Link: https://lore.kernel.org/r/20240312104757.27333-1-luis.henriques@linux.dev Signed-off-by: Christian Brauner

ovl: Always reject mounting over case-insensitive directories

2024-02-27T21:55:34Z

overlayfs relies on the filesystem setting DCACHE_OP_HASH or DCACHE_OP_COMPARE to reject mounting over case-insensitive directories. Since commit bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops"), we set ->d_op through a hook in ->d_lookup, which means the root dentry won't have them, causing the mount to accidentally succeed. In v6.7-rc7, the following sequence will succeed to mount, but any dentry other than the root dentry will be a "weird" dentry to ovl and fail with EREMOTE. mkfs.ext4 -O casefold lower.img mount -O loop lower.img lower mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work ovl /mnt Mounting on a subdirectory fails, as expected, because DCACHE_OP_HASH and DCACHE_OP_COMPARE are properly set by ->lookup. Fix by explicitly rejecting superblocks that allow case-insensitive dentries. Yes, this will be solved when we move d_op configuration back to ->s_d_op. Yet, we better have an explicit fix to avoid messing up again. While there, re-sort the entries to have more descriptive error messages first. Fixes: bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops") Acked-by: Amir Goldstein Reviewed-by: Eric Biggers Link: https://lore.kernel.org/r/20240221171412.10710-2-krisman@suse.de Signed-off-by: Gabriel Krisman Bertazi

ovl: remove redundant ofs->indexdir member

2023-11-20T07:49:09Z

When the index feature is disabled, ofs->indexdir is NULL. When the index feature is enabled, ofs->indexdir has the same value as ofs->workdir and takes an extra reference. This makes the code harder to understand when it is not always clear that ofs->indexdir in one function is the same dentry as ofs->workdir in another function. Remove this redundancy, by referencing ofs->workdir directly in index helpers and by using the ovl_indexdir() accessor in generic code. Signed-off-by: Amir Goldstein

ovl: fix memory leak in ovl_parse_param()

2023-11-14T06:09:36Z

On failure to parse parameters in ovl_parse_param_lowerdir(), it is necessary to update ctx->nr with the correct nr before using ovl_reset_lowerdirs() to release l->name. Reported-and-tested-by: syzbot+26eedf3631650972f17c@syzkaller.appspotmail.com Fixes: c835110b588a ("ovl: remove unused code in lowerdir param parsing") Co-authored-by: Edward Adam Davis Signed-off-by: Amir Goldstein

ovl: add support for appending lowerdirs one by one

2023-10-30T22:13:02Z

Add new mount options lowerdir+ and datadir+ that can be used to add layers to lower layers stack one by one. Unlike the legacy lowerdir mount option, special characters (i.e. colons and cammas) are not unescaped with these new mount options. The new mount options can be repeated to compose a large stack of lower layers, but they may not be mixed with the lagacy lowerdir mount option, because for displaying lower layers in mountinfo, we do not want to mix escaped with unescaped lower layers path syntax. Similar to data-only layer rules with the lowerdir mount option, the datadir+ option must follow at least one lowerdir+ option and the lowerdir+ option must not follow the datadir+ option. If the legacy lowerdir mount option follows lowerdir+ and datadir+ mount options, it overrides them. Sepcifically, calling: fsconfig(FSCONFIG_SET_STRING, "lowerdir", "", 0); can be used to reset previously setup lower layers. Suggested-by: Miklos Szeredi Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/ Signed-off-by: Amir Goldstein

ovl: refactor layer parsing helpers

2023-10-30T22:13:02Z

In preparation for new mount options to add lowerdirs one by one, generalize ovl_parse_param_upperdir() into helper ovl_parse_layer() that will be used for parsing a single lower layers. Suggested-by: Miklos Szeredi Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/ Signed-off-by: Amir Goldstein

ovl: store and show the user provided lowerdir mount option

2023-10-30T22:13:02Z

We are about to add new mount options for adding lowerdir one by one, but those mount options will not support escaping. For the existing case, where lowerdir mount option is provided as a colon separated list, store the user provided (possibly escaped) string and display it as is when showing the lowerdir mount option. Signed-off-by: Amir Goldstein

ovl: remove unused code in lowerdir param parsing

2023-10-30T22:13:02Z

Commit beae836e9c61 ("ovl: temporarily disable appending lowedirs") removed the ability to append lowerdirs with syntax lowerdir=":". Remove leftover code and comments that are irrelevant with lowerdir append mode disabled. Signed-off-by: Amir Goldstein

ovl: temporarily disable appending lowedirs

2023-10-14T19:42:45Z

Kernel v6.5 converted overlayfs to new mount api. As an added bonus, it also added a feature to allow appending lowerdirs using lowerdir=:/lower2,lowerdir=::/data3 syntax. This new syntax has raised some concerns regarding escaping of colons. We decided to try and disable this syntax, which hasn't been in the wild for so long and introduce it again in 6.7 using explicit mount options lowerdir+=/lower2,datadir+=/data3. Suggested-by: Miklos Szeredi Link: https://lore.kernel.org/r/CAJfpegsr3A4YgF2YBevWa6n3=AcP7hNndG6EPMu3ncvV-AM71A@mail.gmail.com/ Fixes: b36a5780cb44 ("ovl: modify layer parameter parsing") Signed-off-by: Amir Goldstein