On 6/3/26 14:32, Vasileios Almpanis wrote:
In legacy mount callpaths, userspace might pass mount options as
flags. These flags escape our checks in ve_devmnt_process allowing
devices to be mounted inside containers with options not specified in
...
+/*
+ * For legacy mount(2), MS_* mount flags are folded into fc->sb_flags and are
+ * not present in the monolithic data string. Build a page with user data
+ * followed by those flags for ve_devmnt checks in vfs_parse_monolithic_sep.
+ *
+ * Returns @data when nothing needs to be added, a new page otherwise, or
+ * ERR_PTR() on failure. The caller must free_page() when the result != @data.
+ */
+void *legacy_merge_mount_data(struct fs_context *fc, void *data)
+{
+ struct ve_struct *ve = get_exec_env();
+ size_t off = 0;
+ char *page;
+ int err;
+
+ if (ve_is_super(ve))
+ return data;
+
+ if (!fc->fs_type || !(fc->fs_type->fs_flags & FS_REQUIRES_DEV))
+ return data;
+
+ /*
+ * Filesystems with binary mount data (e.g. btrfs) bypass option
+ * string parsing entirely, so our checks cannot apply here.
+ */
+ if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
+ return data;
+
+ page = (char *)__get_free_page(GFP_KERNEL);
+ if (!page)
+ return ERR_PTR(-ENOMEM);
+
+ if (data && *(char *)data) {
+ ssize_t ret = strscpy(page, data, PAGE_SIZE);
+
+ if (ret < 0) {
+ err = -E2BIG;
+ goto err_free;
+ }
+ off = ret;
+ }
+
+ err = vfs_format_sb_flags(fc, page, PAGE_SIZE, &off);
+ if (err)
+ goto err_free;
+
+ if (!off) {
Let's drop this check. It happens only when data is empty and no flags provided.
And it doesn't add any value - we just free page a little bit earlier.
Everything else looks good.
+ free_page((unsigned long)page);
+ return data;
+ }
+
+ return page;
+
+err_free:
+ free_page((unsigned long)page);
+ return ERR_PTR(err);
+}
...
--
Best regards, Riabchun Vladimir
Linux Kernel Developer, Virtuozzo
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