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Eric W. Biederman 7f78e03513 fs: Limit sys_mount to only request filesystem modules. ... Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>		12 years ago
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Kconfig	f2fs: resolve build failures	12 years ago
Makefile	f2fs: update Kconfig and Makefile	12 years ago
acl.c	f2fs: avoid null dereference in f2fs_acl_from_disk	12 years ago
acl.h	f2fs: adjust kernel coding style	12 years ago
checkpoint.c	f2fs: clarify and enhance the f2fs_gc flow	12 years ago
data.c	f2fs: support swapfile	12 years ago
debug.c	f2fs: add device name in debugfs	12 years ago
dir.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	12 years ago
f2fs.h	Merge branch 'f2fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into dev	12 years ago
file.c	more file_inode() open-coded instances	12 years ago
gc.c	f2fs: fix calculation of max. gc cost in the SSR case	12 years ago
gc.h	f2fs: clarify and enhance the f2fs_gc flow	12 years ago
hash.c	f2fs: unify string length declarations and usage	12 years ago
inode.c	f2fs: avoid balanc_fs during evict_inode	12 years ago
namei.c	f2fs: unify string length declarations and usage	12 years ago
node.c	f2fs: avoid build warning	12 years ago
node.h	f2fs: adjust kernel coding style	12 years ago
recovery.c	Merge branch 'f2fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into dev	12 years ago
segment.c	f2fs: clarify and enhance the f2fs_gc flow	12 years ago
segment.h	f2fs: clarify and enhance the f2fs_gc flow	12 years ago
super.c	fs: Limit sys_mount to only request filesystem modules.	12 years ago
xattr.c	f2fs: add f2fs_balance_fs in several interfaces	12 years ago
xattr.h	f2fs: adjust kernel coding style	12 years ago