[PATCH 6.6 091/638] ovl: refactor layer parsing helpers

Sasha Levin
2024-03-24T23:02:47Z

From: Amir Goldstein <amir73il@gmail.com>

[ Upstream commit 819829f0319a759e8a6ccb7e4f1113f3f9f07aa3 ]

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 <miklos@szeredi.hu>
Link: https://lore.kernel.org/r/CAJfpegt7VC94KkRtb1dfHG8+4OzwPBLYqhtc8=QFUxpFJE+=RQ@mail.gmail.com/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Stable-dep-of: 2824083db76c ("ovl: Always reject mounting over case-insensitive directories")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/overlayfs/params.c | 121 +++++++++++++++++++++++-------------------
1 file changed, 67 insertions(+), 54 deletions(-)

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index 0bf754a69e919..88725982b6dd3 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -43,7 +43,7 @@ module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
MODULE_PARM_DESC(metacopy,
"Default to on or off for the metadata only copy up feature");

-enum {
+enum ovl_opt {
Opt_lowerdir,
Opt_upperdir,
Opt_workdir,
@@ -238,19 +238,8 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
pr_err("failed to resolve '%s': %i\n", name, err);
goto out;
}
- err = -EINVAL;
- if (ovl_dentry_weird(path->dentry)) {
- pr_err("filesystem on '%s' not supported\n", name);
- goto out_put;
- }
- if (!d_is_dir(path->dentry)) {
- pr_err("'%s' not a directory\n", name);
- goto out_put;
- }
return 0;

-out_put:
- path_put_init(path);
out:
return err;
}
@@ -268,7 +257,7 @@ static void ovl_unescape(char *s)
}
}

-static int ovl_mount_dir(const char *name, struct path *path, bool upper)
+static int ovl_mount_dir(const char *name, struct path *path)
{
int err = -ENOMEM;
char *tmp = kstrdup(name, GFP_KERNEL);
@@ -276,60 +265,82 @@ static int ovl_mount_dir(const char *name, struct path *path, bool upper)
if (tmp) {
ovl_unescape(tmp);
err = ovl_mount_dir_noesc(tmp, path);
-
- if (!err && upper && path->dentry->d_flags & DCACHE_OP_REAL) {
- pr_err("filesystem on '%s' not supported as upperdir\n",
- tmp);
- path_put_init(path);
- err = -EINVAL;
- }
kfree(tmp);
}
return err;
}

-static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
- bool workdir)
+static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
+ enum ovl_opt layer, const char *name, bool upper)
{
- int err;
- struct ovl_fs *ofs = fc->s_fs_info;
- struct ovl_config *config = &ofs->config;
- struct ovl_fs_context *ctx = fc->fs_private;
- struct path path;
- char *dup;
+ if (ovl_dentry_weird(path->dentry))
+ return invalfc(fc, "filesystem on %s not supported", name);

- err = ovl_mount_dir(name, &path, true);
- if (err)
- return err;
+ if (!d_is_dir(path->dentry))
+ return invalfc(fc, "%s is not a directory", name);

/*
* Check whether upper path is read-only here to report failures
* early. Don't forget to recheck when the superblock is created
* as the mount attributes could change.
*/
- if (__mnt_is_readonly(path.mnt)) {
- path_put(&path);
- return -EINVAL;
+ if (upper) {
+ if (path->dentry->d_flags & DCACHE_OP_REAL)
+ return invalfc(fc, "filesystem on %s not supported as upperdir", name);
+ if (__mnt_is_readonly(path->mnt))
+ return invalfc(fc, "filesystem on %s is read-only", name);
}
+ return 0;
+}

- dup = kstrdup(name, GFP_KERNEL);
- if (!dup) {
- path_put(&path);
- return -ENOMEM;
- }
+static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
+ struct path *path, char **pname)
+{
+ struct ovl_fs *ofs = fc->s_fs_info;
+ struct ovl_config *config = &ofs->config;
+ struct ovl_fs_context *ctx = fc->fs_private;

- if (workdir) {
- kfree(config->workdir);
- config->workdir = dup;
- path_put(&ctx->work);
- ctx->work = path;
- } else {
- kfree(config->upperdir);
- config->upperdir = dup;
- path_put(&ctx->upper);
- ctx->upper = path;
+ switch (layer) {
+ case Opt_workdir:
+ swap(config->workdir, *pname);
+ swap(ctx->work, *path);
+ break;
+ case Opt_upperdir:
+ swap(config->upperdir, *pname);
+ swap(ctx->upper, *path);
+ break;
+ default:
+ WARN_ON(1);
}
- return 0;
+}
+
+static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
+ enum ovl_opt layer)
+{
+ char *name = kstrdup(param->string, GFP_KERNEL);
+ bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
+ struct path path;
+ int err;
+
+ if (!name)
+ return -ENOMEM;
+
+ err = ovl_mount_dir(name, &path);
+ if (err)
+ goto out_free;
+
+ err = ovl_mount_dir_check(fc, &path, layer, name, upper);
+ if (err)
+ goto out_put;
+
+ /* Store the user provided path string in ctx to show in mountinfo */
+ ovl_add_layer(fc, layer, &path, &name);
+
+out_put:
+ path_put(&path);
+out_free:
+ kfree(name);
+ return err;
}

static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
@@ -417,7 +428,11 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
for (nr = 0; nr < nr_lower; nr++, l++) {
memset(l, 0, sizeof(*l));

- err = ovl_mount_dir(iter, &l->path, false);
+ err = ovl_mount_dir(iter, &l->path);
+ if (err)
+ goto out_put;
+
+ err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
if (err)
goto out_put;

@@ -505,10 +520,8 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
err = ovl_parse_param_lowerdir(param->string, fc);
break;
case Opt_upperdir:
- fallthrough;
case Opt_workdir:
- err = ovl_parse_param_upperdir(param->string, fc,
- (Opt_workdir == opt));
+ err = ovl_parse_layer(fc, param, opt);
break;
case Opt_default_permissions:
config->default_permissions = true;
--
2.43.0