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 the allowed field. Introduce helpers that take these flags and already existing tables of flag -> string representation to construct a comma separated value string from them, and append them to userspace provided data. Then pass this string to parse_monolithic_mount_data enforcing the same checks symmetrically in both mount and fsconfig syscalls.
In the remount path, run legacy_merge_mount_data() before ve_devmnt_process() so container device mount policy sees MS_* flags from the legacy mount(2) API, not only the user-supplied option string. Keep ve_prepare_mount_options() for legacy parsers that do not use generic_parse_monolithic(). https://virtuozzo.atlassian.net/browse/VSTOR-132330 Signed-off-by: Vasileios Almpanis <[email protected]> Feature: ve: ve generic structures --- Changes since v2: - Remove legacy_merge_mount_data guard in fs/internal.h. All helpers don't use anything that would break build and just unchanged pointer will be returned. - Add __vfs_format_flags helper and use it in vfs_format_sb_flags - Fix inconsistent error code: replace -ENOSPC with -E2BIG for the buffer-too-small case Changes since v1: - Replace open-coded flag loops with append_entry() helper (pointer- advancing style) that unifies the comma-insert-copy pattern across all three call sites - Rework legacy_merge_mount_data() to allocate the page upfront, write user data first then append sb flags via vfs_format_sb_flags(); this eliminates the intermediate flags_buf[128], the total size calculation, and the +1/+2 arithmetic - Fix inconsistent error code: replace -EINVAL with -ENOSPC for the buffer-too-small case - Add comment on FS_BINARY_MOUNTDATA explaining why those filesystems are skipped - Add blank line before return in legacy_merge_mount_data() - Remove excess blank line after parse_monolithic_mount_data() in do_remount() fs/fs_context.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++ fs/internal.h | 1 + fs/namespace.c | 32 +++++++++++--- 3 files changed, 137 insertions(+), 7 deletions(-) diff --git a/fs/fs_context.c b/fs/fs_context.c index 76f34f3d468e..353d1eea77d0 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -81,6 +81,117 @@ static int vfs_parse_sb_flag(struct fs_context *fc, const char *key) return -ENOPARAM; } +/* + * Emit, into @buff at *@off, the comma-separated names of every entry in @p + * whose bit is set in @flags. Advances *@off past the written text. + * Returns 0 on success or -E2BIG if the buffer is too small. + */ +static int __vfs_format_flags(const struct constant_table *p, unsigned int flags, + char *buff, size_t size, size_t *off) +{ + for (; p->name; p++) { + ssize_t ret; + + if (!(flags & p->value)) + continue; + + if (*off) { + if (*off + 1 >= size) + return -E2BIG; + buff[(*off)++] = ','; + } + + ret = strscpy(buff + *off, p->name, size - *off); + if (ret < 0) + return -E2BIG; + *off += ret; + } + return 0; +} + +/* + * Append fc's sb flags as comma-separated option names into @buff, advancing + * *@off. Matches vfs_parse_sb_flag() / common_{set,clear}_sb_flag tables. + */ +static int vfs_format_sb_flags(struct fs_context *fc, char *buff, size_t size, + size_t *off) +{ + int ret; + + /* Positive names (ro, sync, ...) for bits that are on. */ + ret = __vfs_format_flags(common_set_sb_flag, fc->sb_flags, + buff, size, off); + if (ret) + return ret; + + /* + * Negative names (rw, async, ...) only for bits being turned off: in + * the mask but off in the value. __vfs_format_flags() emits when + * (arg & bit), so the emit set is "mask & ~flags". + */ + return __vfs_format_flags(common_clear_sb_flag, + fc->sb_flags_mask & ~fc->sb_flags, + buff, size, off); +} + +/* + * 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) { + free_page((unsigned long)page); + return data; + } + + return page; + +err_free: + free_page((unsigned long)page); + return ERR_PTR(err); +} + /** * vfs_parse_fs_param_source - Handle setting "source" via parameter * @fc: The filesystem context to modify diff --git a/fs/internal.h b/fs/internal.h index 0064345cb9d0..147130cab046 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -46,6 +46,7 @@ extern void __init chrdev_init(void); */ extern const struct fs_context_operations legacy_fs_context_ops; extern int parse_monolithic_mount_data(struct fs_context *, void *); +extern void *legacy_merge_mount_data(struct fs_context *fc, void *data); extern void vfs_clean_context(struct fs_context *fc); extern int finish_clean_context(struct fs_context *fc); diff --git a/fs/namespace.c b/fs/namespace.c index acd4507e1247..d4a419a0bca9 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3295,6 +3295,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, struct super_block *sb = path->mnt->mnt_sb; struct mount *mnt = real_mount(path->mnt); struct fs_context *fc; + void *mnt_data = NULL; if (!check_mnt(mnt)) return -EINVAL; @@ -3315,13 +3316,17 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, */ fc->oldapi = true; - err = ve_prepare_mount_options(fc, data); - if (err) { - put_fs_context(fc); - return err; + mnt_data = legacy_merge_mount_data(fc, data); + if (IS_ERR(mnt_data)) { + err = PTR_ERR(mnt_data); + goto err; } - err = parse_monolithic_mount_data(fc, data); + err = ve_prepare_mount_options(fc, mnt_data); + if (err) + goto free_mnt_data; + + err = parse_monolithic_mount_data(fc, mnt_data); if (!err) { down_write(&sb->s_umount); err = -EPERM; @@ -3338,6 +3343,10 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, mnt_warn_timestamp_expiry(path, &mnt->mnt); +free_mnt_data: + if (mnt_data != data) + free_page((unsigned long)mnt_data); +err: put_fs_context(fc); return err; } @@ -3774,8 +3783,17 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags, subtype, strlen(subtype)); if (!err && name) err = vfs_parse_fs_string(fc, "source", name, strlen(name)); - if (!err) - err = parse_monolithic_mount_data(fc, data); + if (!err) { + void *mnt_data = legacy_merge_mount_data(fc, data); + + if (IS_ERR(mnt_data)) { + err = PTR_ERR(mnt_data); + } else { + err = parse_monolithic_mount_data(fc, mnt_data); + if (mnt_data != data) + free_page((unsigned long)mnt_data); + } + } if (!err && !mount_capable(fc)) err = -EPERM; if (!err) -- 2.43.0 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
