Many file systems that implement the show_options hook fail to correctly
escape their output which could lead to unescaped characters (e.g. new
lines) leaking into /proc/mounts and /proc/[pid]/mountinfo files. This
could lead to confusion, spoofed entries (resulting in things like
systemd issuing false d-bus "mount" notifications), and who knows what
else. This looks like it would only be the root user stepping on
themselves, but it's possible weird things could happen in containers or
in other situations with delegated mount privileges.
Here's an example using overlay with setuid fusermount trusting the
contents of /proc/mounts (via the /etc/mtab symlink). Imagine the use
of "sudo" is something more sneaky:
$ BASE="ovl"
$ MNT="$BASE/mnt"
$ LOW="$BASE/lower"
$ UP="$BASE/upper"
$ WORK="$BASE/work/ 0 0
none /proc fuse.pwn user_id=1000"
$ mkdir -p "$LOW" "$UP" "$WORK"
$ sudo mount -t overlay -o "lowerdir=$LOW,upperdir=$UP,workdir=$WORK" none /mnt
$ cat /proc/mounts
none /root/ovl/mnt overlay rw,relatime,lowerdir=ovl/lower,upperdir=ovl/upper,workdir=ovl/work/ 0 0
none /proc fuse.pwn user_id=1000 0 0
$ fusermount -u /proc
$ cat /proc/mounts
cat: /proc/mounts: No such file or directory
This fixes the problem by adding new seq_show_option and
seq_show_option_n helpers, and updating the vulnerable show_option
handlers to use them as needed. Some, like SELinux, need to be open
coded due to unusual existing escape mechanisms.
[akpm@linux-foundation.org: add lost chunk, per Kees]
[keescook@chromium.org: seq_show_option should be using const parameters]
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Jan Kara <jack@suse.com>
Acked-by: Paul Moore <paul@paul-moore.com>
Cc: J. R. Okajima <hooanon05g@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
when opening a directory we want the overlayfs inode, not one from
the topmost layer.
Reported-By: Andrey Jr. Melnikov <temnota.am@gmail.com>
Tested-By: Andrey Jr. Melnikov <temnota.am@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull more vfs updates from Al Viro:
"Assorted VFS fixes and related cleanups (IMO the most interesting in
that part are f_path-related things and Eric's descriptor-related
stuff). UFS regression fixes (it got broken last cycle). 9P fixes.
fs-cache series, DAX patches, Jan's file_remove_suid() work"
[ I'd say this is much more than "fixes and related cleanups". The
file_table locking rule change by Eric Dumazet is a rather big and
fundamental update even if the patch isn't huge. - Linus ]
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (49 commits)
9p: cope with bogus responses from server in p9_client_{read,write}
p9_client_write(): avoid double p9_free_req()
9p: forgetting to cancel request on interrupted zero-copy RPC
dax: bdev_direct_access() may sleep
block: Add support for DAX reads/writes to block devices
dax: Use copy_from_iter_nocache
dax: Add block size note to documentation
fs/file.c: __fget() and dup2() atomicity rules
fs/file.c: don't acquire files->file_lock in fd_install()
fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation
vfs: avoid creation of inode number 0 in get_next_ino
namei: make set_root_rcu() return void
make simple_positive() public
ufs: use dir_pages instead of ufs_dir_pages()
pagemap.h: move dir_pages() over there
remove the pointless include of lglock.h
fs: cleanup slight list_entry abuse
xfs: Correctly lock inode when removing suid and file capabilities
fs: Call security_ops->inode_killpriv on truncate
fs: Provide function telling whether file_remove_privs() will do anything
...
Pull overlayfs updates from Miklos Szeredi:
"This relaxes the requirements on the lower layer filesystem: now ones
that implement .d_revalidate, such as NFS, can be used.
Upper layer filesystems still has the "no .d_revalidate" requirement.
Also a bad interaction with jffs2 locking has been fixed"
* 'overlayfs-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: lookup whiteouts outside iterate_dir()
ovl: allow distributed fs as lower layer
ovl: don't traverse automount points
Pull vfs updates from Al Viro:
"In this pile: pathname resolution rewrite.
- recursion in link_path_walk() is gone.
- nesting limits on symlinks are gone (the only limit remaining is
that the total amount of symlinks is no more than 40, no matter how
nested).
- "fast" (inline) symlinks are handled without leaving rcuwalk mode.
- stack footprint (independent of the nesting) is below kilobyte now,
about on par with what it used to be with one level of nested
symlinks and ~2.8 times lower than it used to be in the worst case.
- struct nameidata is entirely private to fs/namei.c now (not even
opaque pointers are being passed around).
- ->follow_link() and ->put_link() calling conventions had been
changed; all in-tree filesystems converted, out-of-tree should be
able to follow reasonably easily.
For out-of-tree conversions, see Documentation/filesystems/porting
for details (and in-tree filesystems for examples of conversion).
That has sat in -next since mid-May, seems to survive all testing
without regressions and merges clean with v4.1"
* 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (131 commits)
turn user_{path_at,path,lpath,path_dir}() into static inlines
namei: move saved_nd pointer into struct nameidata
inline user_path_create()
inline user_path_parent()
namei: trim do_last() arguments
namei: stash dfd and name into nameidata
namei: fold path_cleanup() into terminate_walk()
namei: saner calling conventions for filename_parentat()
namei: saner calling conventions for filename_create()
namei: shift nameidata down into filename_parentat()
namei: make filename_lookup() reject ERR_PTR() passed as name
namei: shift nameidata inside filename_lookup()
namei: move putname() call into filename_lookup()
namei: pass the struct path to store the result down into path_lookupat()
namei: uninline set_root{,_rcu}()
namei: be careful with mountpoint crossings in follow_dotdot_rcu()
Documentation: remove outdated information from automount-support.txt
get rid of assorted nameidata-related debris
lustre: kill unused helper
lustre: kill unused macro (LOOKUP_CONTINUE)
...
If jffs2 can deadlock on overlayfs readdir because it takes the same lock
on ->iterate() as in ->lookup().
Fix by moving whiteout checking outside iterate_dir(). Optimized by
collecting potential whiteouts (DT_CHR) in a temporary list and if
non-empty iterating throug these and checking for a 0/0 chardev.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Fixes: 49c21e1cac ("ovl: check whiteout while reading directory")
Reported-by: Roman Yeryomin <leroi.lists@gmail.com>
Allow filesystems with .d_revalidate as lower layer(s), but not as upper
layer.
For local filesystems the rule was that modifications on the layers
directly while being part of the overlay results in undefined behavior.
This can easily be extended to distributed filesystems: we assume the tree
used as lower layer is static, which means ->d_revalidate() should always
return "1". If that is not the case, return -ESTALE, don't try to work
around the modification.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
NFS and other distributed filesystems may place automount points in the
tree. Previoulsy overlayfs refused to mount such filesystems types (based
on the existence of the .d_automount callback), even if the actual export
didn't have any automount points.
It cannot be determined in advance whether the filesystem has automount
points or not. The solution is to allow fs with .d_automount but refuse to
traverse any automount points encountered.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Make file->f_path always point to the overlay dentry so that the path in
/proc/pid/fd is correct and to ensure that label-based LSMs have access to the
overlay as well as the underlay (path-based LSMs probably don't need it).
Using my union testsuite to set things up, before the patch I see:
[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
...
lr-x------. 1 root root 64 Jun 5 14:38 5 -> /a/foo107
[root@andromeda union-testsuite]# stat /mnt/a/foo107
...
Device: 23h/35d Inode: 13381 Links: 1
...
[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
...
Device: 23h/35d Inode: 13381 Links: 1
...
After the patch:
[root@andromeda union-testsuite]# bash 5</mnt/a/foo107
[root@andromeda union-testsuite]# ls -l /proc/$$/fd/
...
lr-x------. 1 root root 64 Jun 5 14:22 5 -> /mnt/a/foo107
[root@andromeda union-testsuite]# stat /mnt/a/foo107
...
Device: 23h/35d Inode: 40346 Links: 1
...
[root@andromeda union-testsuite]# stat -L /proc/$$/fd/5
...
Device: 23h/35d Inode: 40346 Links: 1
...
Note the change in where /proc/$$/fd/5 points to in the ls command. It was
pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107
(which is correct).
The inode accessed, however, is the lower layer. The union layer is on device
25h/37d and the upper layer on 24h/36d.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Call ovl_drop_write() earlier in ovl_dentry_open() before we call vfs_open()
as we've done the copy up for which we needed the freeze-write lock by that
point.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
OpenWRT folks reported that overlayfs fails to mount if upper fs is full,
because workdir can't be created. Wordir creation can fail for various
other reasons too.
There's no reason that the mount itself should fail, overlayfs can work
fine without a workdir, as long as the overlay isn't modified.
So mount it read-only and don't allow remounting read-write.
Add a couple of WARN_ON()s for the impossible case of workdir being used
despite being read-only.
Reported-by: Bastian Bittorf <bittorf@bluebottle.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: <stable@vger.kernel.org> # v3.18+
When removing an opaque directory we can't just call rmdir() to check for
emptiness, because the directory will need to be replaced with a whiteout.
The replacement is done with RENAME_EXCHANGE, which doesn't check
emptiness.
Solution is just to check emptiness by reading the directory. In the
future we could add a new rename flag to check for emptiness even for
RENAME_EXCHANGE to optimize this case.
Reported-by: Vincent Batts <vbatts@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Jordi Pujol Palomer <jordipujolp@gmail.com>
Fixes: 263b4a0fee ("ovl: dont replace opaque dir")
Cc: <stable@vger.kernel.org> # v4.0+
a) instead of storing the symlink body (via nd_set_link()) and returning
an opaque pointer later passed to ->put_link(), ->follow_link() _stores_
that opaque pointer (into void * passed by address by caller) and returns
the symlink body. Returning ERR_PTR() on error, NULL on jump (procfs magic
symlinks) and pointer to symlink body for normal symlinks. Stored pointer
is ignored in all cases except the last one.
Storing NULL for opaque pointer (or not storing it at all) means no call
of ->put_link().
b) the body used to be passed to ->put_link() implicitly (via nameidata).
Now only the opaque pointer is. In the cases when we used the symlink body
to free stuff, ->follow_link() now should store it as opaque pointer in addition
to returning it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
ovl_follow_link current calls ->put_link on an error path.
However ->put_link is about to change in a way that it will be
impossible to call it from ovl_follow_link.
So rearrange the code to avoid the need for that error path.
Specifically: move the kmalloc() call before the ->follow_link()
call to the subordinate filesystem.
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
After importing multi-lower layer support, users could mount a r/o
partition as the left most lowerdir instead of using it as upperdir.
And a r/o upperdir may cause an error like
overlayfs: failed to create directory ./workdir/work
during mount.
This patch check the *s_flags* of upper fs and return an error if
it is a r/o partition. The checking of *upper_mnt->mnt_sb->s_flags*
can be removed now.
This patch also remove
/* FIXME: workdir is not needed for a R/O mount */
from ovl_fill_super() because:
1) for upper fs r/o case
Setting a r/o partition as upper is prevented, no need to care about
workdir in this case.
2) for "mount overlay -o ro" with a r/w upper fs case
Users could remount overlayfs to r/w in this case, so workdir should
not be omitted.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Recently multi-lower layer mount support allow upperdir and workdir
to be omitted, then cause overlayfs can be mount with only one
lowerdir directory. This action make no sense and have potential risk.
This patch check the total number of lower directories to prevent
mounting overlayfs with only one directory.
Also, an error message is added to indicate lower directories exceed
OVL_MAX_STACK limit.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Overlayfs should print an error message if an incorrect mount option
is caught like other filesystems.
After this patch, improper option input could be clearly known.
Reported-by: Fabian Sturm <fabian.sturm@aduu.de>
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Convert the following where appropriate:
(1) S_ISLNK(dentry->d_inode) to d_is_symlink(dentry).
(2) S_ISREG(dentry->d_inode) to d_is_reg(dentry).
(3) S_ISDIR(dentry->d_inode) to d_is_dir(dentry). This is actually more
complicated than it appears as some calls should be converted to
d_can_lookup() instead. The difference is whether the directory in
question is a real dir with a ->lookup op or whether it's a fake dir with
a ->d_automount op.
In some circumstances, we can subsume checks for dentry->d_inode not being
NULL into this, provided we the code isn't in a filesystem that expects
d_inode to be NULL if the dirent really *is* negative (ie. if we're going to
use d_inode() rather than d_backing_inode() to get the inode pointer).
Note that the dentry type field may be set to something other than
DCACHE_MISS_TYPE when d_inode is NULL in the case of unionmount, where the VFS
manages the fall-through from a negative dentry to a lower layer. In such a
case, the dentry type of the negative union dentry is set to the same as the
type of the lower dentry.
However, if you know d_inode is not NULL at the call site, then you can use
the d_is_xxx() functions even in a filesystem.
There is one further complication: a 0,0 chardev dentry may be labelled
DCACHE_WHITEOUT_TYPE rather than DCACHE_SPECIAL_TYPE. Strictly, this was
intended for special directory entry types that don't have attached inodes.
The following perl+coccinelle script was used:
use strict;
my @callers;
open($fd, 'git grep -l \'S_IS[A-Z].*->d_inode\' |') ||
die "Can't grep for S_ISDIR and co. callers";
@callers = <$fd>;
close($fd);
unless (@callers) {
print "No matches\n";
exit(0);
}
my @cocci = (
'@@',
'expression E;',
'@@',
'',
'- S_ISLNK(E->d_inode->i_mode)',
'+ d_is_symlink(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISDIR(E->d_inode->i_mode)',
'+ d_is_dir(E)',
'',
'@@',
'expression E;',
'@@',
'',
'- S_ISREG(E->d_inode->i_mode)',
'+ d_is_reg(E)' );
my $coccifile = "tmp.sp.cocci";
open($fd, ">$coccifile") || die $coccifile;
print($fd "$_\n") || die $coccifile foreach (@cocci);
close($fd);
foreach my $file (@callers) {
chomp $file;
print "Processing ", $file, "\n";
system("spatch", "--sp-file", $coccifile, $file, "--in-place", "--no-show-diff") == 0 ||
die "spatch failed";
}
[AV: overlayfs parts skipped]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Since the ovl_dir_cache is stable during a directory reading, the cursor
of struct ovl_dir_file don't need to be an independent entry in the list
of a merged directory.
This patch changes *cursor* to a pointer which points to the entry in the
ovl_dir_cache. After this, we don't need to check *is_cursor* either.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Overlayfs should be mounted read-only when upper-fs is read-only or nonexistent.
But now it can be remounted read-write and this can cause kernel panic.
So we should prevent read-write remount when the above situation happens.
Signed-off-by: Seunghun Lee <waydi1@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Current multi-layer support overlayfs has a regression in
.lookup(). If there is a directory in upperdir and a regular
file has same name in lowerdir in a merged directory, lower
file is hidden and upper directory is set to opaque in former
case. But it is changed in present code.
In lowerdir lookup path, if a found inode is not directory,
the type checking of previous inode is missing. This inode
will be copied to the lowerstack of ovl_entry directly.
That will lead to several wrong conditions, for example,
the reading of the directory in upperdir may return an error
like:
ls: reading directory .: Not a directory
This patch makes the lowerdir lookup path check the opaque
for non-directory file too.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
The function ovl_fill_super() in recently multi-layer support
version will incorrectly return 0 at error handling path and
then cause kernel panic.
This failure can be reproduced by mounting a overlayfs with
upperdir and workdir in different mounts.
And also, If the memory allocation of *lower_mnt* fail, this
function may return an zero either.
This patch fix this problem by setting *err* to proper error
number before jumping to error handling path.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This patch adds two macros:
OVL_XATTR_PRE_NAME and OVL_XATTR_PRE_LEN
to present ovl_xattr name prefix and its length. Also, a
new macro OVL_XATTR_OPAQUE is introduced to replace old
*ovl_opaque_xattr*.
Fix the length of "trusted.overlay." to *16*.
Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Allow "lowerdir=" option to contain multiple lower directories separated by
a colon (e.g. "lowerdir=/bin:/usr/bin"). Colon characters in filenames can
be escaped with a backslash.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Make "upperdir=" mount option optional. If "upperdir=" is not given, then
the "workdir=" option is also optional (and ignored if given).
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Move allocation of root entry above to where it's needed.
Move initializations related to upperdir and workdir near each other.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
"Suppose you have in one of the lower layers a filesystem with
->lookup()-enforced upper limit on name length. Pretty much every local fs
has one, but... they are not all equal. 255 characters is the common upper
limit, but e.g. jffs2 stops at 254, minixfs upper limit is somewhere from
14 to 60, depending upon version, etc. You are doing a lookup for
something that is present in upper layer, but happens to be too long for
one of the lower layers. Too bad - ENAMETOOLONG for you..."
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Not checking whiteouts on lowest layer was an optimization (there's nothing
to white out there), but it could result in inconsitent behavior when a
layer previously used as upper/middle is later used as lowest.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
If multiple lower layers exist, merge them as well in readdir according to
the same rules as merging upper with lower. I.e. take whiteouts and opaque
directories into account on all but the lowers layer.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Add helper to iterate through all the layers, starting from the upper layer
(if exists) and continuing down through the lower layers.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Add multiple lower layers to 'struct ovl_fs' and 'struct ovl_entry'.
ovl_entry will have an array of paths, instead of just the dentry. This
allows a compact array containing just the layers which exist at current
point in the tree (which is expected to be a small number for the majority
of dentries).
The number of layers is not limited by this infrastructure.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
When removing an empty opaque directory, then it makes no sense to replace
it with an exact replica of itself before removal.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Don't make a separate pass for checking whiteouts, since we can do it while
reading the upper directory.
This will make it easier to handle multiple layers.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Check against !OVL_PATH_LOWER instead of OVL_PATH_MERGE. For a copied up
directory the two are currently equivalent.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Pass dentry into ovl_dir_read_merged() insted of upperpath and lowerpath.
This cleans up callers and paves the way for multi-layer directory reads.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Xattr operations can race with copy up. This does not matter as long as
we consistently fiter out "trunsted.overlay.opaque" attribute on upper
directories.
Previously we checked parent against OVL_PATH_MERGE. This is too general,
and prone to race with copy-up. I.e. we found the parent to be on the
lower layer but ovl_dentry_real() would return the copied-up dentry,
possibly with the "opaque" attribute.
So instead use ovl_path_real() and decide to filter the attributes based on
the actual type of the dentry we'll use.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
ovl_remove_and_whiteout() needs to check if upper dentry exists or not
after having locked upper parent directory.
Previously we used a "type" value computed before locking the upper parent
directory, which is susceptible to racing with copy-up.
There's a similar check in ovl_check_empty_and_clear(). This one is not
actually racy, since copy-up doesn't change the "emptyness" property of a
directory. Add a comment to this effect, and check the existence of upper
dentry locally to make the code cleaner.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Some distributions carry an "old" format of overlayfs while mainline has a
"new" format.
The distros will possibly want to keep the old overlayfs alongside the new
for compatibility reasons.
To make it possible to differentiate the two versions change the name of
the new one from "overlayfs" to "overlay".
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reported-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Andy Whitcroft <apw@canonical.com>
ovl_cache_put() can be called from ovl_dir_reset() if the cache needs to be
rebuilt. We did list_del() on the cursor, which results in an Oops on the
poisoned pointer in ovl_seek_cursor().
Reported-by: Jordi Pujol Palomer <jordipujolp@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Jordi Pujol Palomer <jordipujolp@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Kees Cook