Workdir creation fails in latest kernel.
Fix by allowing EOPNOTSUPP as a valid return value from
vfs_removexattr(XATTR_NAME_POSIX_ACL_*). Upper filesystem may not support
ACL and still be perfectly able to support overlayfs.
Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: c11b9fdd6a ("ovl: remove posix_acl_default from workdir")
Cc: <stable@vger.kernel.org>
Now that overlayfs has xattr handlers for iop->{set,remove}xattr, use
those same handlers for iop->getxattr as well.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Setting POSIX acl may also modify the file mode, so need to copy that up to
the overlay inode.
Reported-by: Eryu Guan <eguan@redhat.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Commit d837a49bd5 ("ovl: fix POSIX ACL setting") switches from
iop->setxattr from ovl_setxattr to generic_setxattr, so switch from
ovl_removexattr to generic_removexattr as well. As far as permission
checking goes, the same rules should apply in either case.
While doing that, rename ovl_setxattr to ovl_xattr_set to indicate that
this is not an iop->setxattr implementation and remove the unused inode
argument.
Move ovl_other_xattr_set above ovl_own_xattr_set so that they match the
order of handlers in ovl_xattr_handlers.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Use an ordinary #ifdef to conditionally include the POSIX ACL handlers
in ovl_xattr_handlers, like the other filesystems do. Flag the code
that is now only used conditionally with __maybe_unused.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Trivial fix to spelling mistake in pr_err message.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
When mounting overlayfs it needs a clean "work" directory under the
supplied workdir.
Previously the mount code removed this directory if it already existed and
created a new one. If the removal failed (e.g. directory was not empty)
then it fell back to a read-only mount not using the workdir.
While this has never been reported, it is possible to get a non-empty
"work" dir from a previous mount of overlayfs in case of crash in the
middle of an operation using the work directory.
In this case the left over state should be discarded and the overlay
filesystem will be consistent, guaranteed by the atomicity of operations on
moving to/from the workdir to the upper layer.
This patch implements cleaning out any files left in workdir. It is
implemented using real recursion for simplicity, but the depth is limited
to 2, because the worst case is that of a directory containing whiteouts
under "work".
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Clear out posix acl xattrs on workdir and also reset the mode after
creation so that an inherited sgid bit is cleared.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
This does not work and does not make sense. So instead of fixing it
(probably not hard) just disallow.
Reported-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
Setting POSIX ACL needs special handling:
1) Some permission checks are done by ->setxattr() which now uses mounter's
creds ("ovl: do operations on underlying file system in mounter's
context"). These permission checks need to be done with current cred as
well.
2) Setting ACL can fail for various reasons. We do not need to copy up in
these cases.
In the mean time switch to using generic_setxattr.
[Arnd Bergmann] Fix link error without POSIX ACL. posix_acl_from_xattr()
doesn't have a 'static inline' implementation when CONFIG_FS_POSIX_ACL is
disabled, and I could not come up with an obvious way to do it.
This instead avoids the link error by defining two sets of ACL operations
and letting the compiler drop one of the two at compile time depending
on CONFIG_FS_POSIX_ACL. This avoids all references to the ACL code,
also leading to smaller code.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Inode attributes are copied up to overlay inode (uid, gid, mode, atime,
mtime, ctime) so generic code using these fields works correcty. If a hard
link is created in overlayfs separate inodes are allocated for each link.
If chmod/chown/etc. is performed on one of the links then the inode
belonging to the other ones won't be updated.
This patch attempts to fix this by sharing inodes for hard links.
Use inode hash (with real inode pointer as a key) to make sure overlay
inodes are shared for hard links on upper. Hard links on lower are still
split (which is not user observable until the copy-up happens, see
Documentation/filesystems/overlayfs.txt under "Non-standard behavior").
The inode is only inserted in the hash if it is non-directoy and upper.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
To get from overlay inode to real inode we currently use 'struct
ovl_entry', which has lifetime connected to overlay dentry. This is okay,
since each overlay dentry had a new overlay inode allocated.
Following patch will break that assumption, so need to leave out ovl_entry.
This patch stores the real inode directly in i_private, with the lowest bit
used to indicate whether the inode is upper or lower.
Lifetime rules remain, using ovl_inode_real() must only be done while
caller holds ref on overlay dentry (and hence on real dentry), or within
RCU protected regions.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fix atime update logic in overlayfs.
This patch adds an i_op->update_time() handler to overlayfs inodes. This
forwards atime updates to the upper layer only. No atime updates are done
on lower layers.
Remove implicit atime updates to underlying files and directories with
O_NOATIME. Remove explicit atime update in ovl_readlink().
Clear atime related mnt flags from cloned upper mount. This means atime
updates are controlled purely by overlayfs mount options.
Reported-by: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The fact that we always do permission checking on the overlay inode and
clear MAY_WRITE for checking access to the lower inode allows cruft to be
removed from ovl_permission().
1) "default_permissions" option effectively did generic_permission() on the
overlay inode with i_mode, i_uid and i_gid updated from underlying
filesystem. This is what we do by default now. It did the update using
vfs_getattr() but that's only needed if the underlying filesystem can
change (which is not allowed). We may later introduce a "paranoia_mode"
that verifies that mode/uid/gid are not changed.
2) splitting out the IS_RDONLY() check from inode_permission() also becomes
unnecessary once we remove the MAY_WRITE from the lower inode check.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Now we are planning to do DAC permission checks on overlay inode
itself. And to make it work, we will need to make sure we can get acls from
underlying inode. So define ->get_acl() for overlay inodes and this in turn
calls into underlying filesystem to get acls, if any.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The hash salting changes meant that we can no longer reuse the hash in the
overlay dentry to look up the underlying dentry.
Instead of lookup_hash(), use lookup_one_len_unlocked() and swith to
mounter's creds (like we do for all other operations later in the series).
Now the lookup_hash() export introduced in 4.6 by 3c9fe8cdff ("vfs: add
lookup_hash() helper") is unused and can possibly be removed; its
usefulness negated by the hash salting and the idea that mounter's creds
should be used on operations on underlying filesystems.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 8387ff2577 ("vfs: make the string hashes salt the hash")
overlay needs underlying fs to support d_type. Recently I put in a
patch in to detect this condition and started failing mount if
underlying fs did not support d_type.
But this breaks existing configurations over kernel upgrade. Those who
are running docker (partially broken configuration) with xfs not
supporting d_type, are surprised that after kernel upgrade docker does
not run anymore.
https://github.com/docker/docker/issues/22937#issuecomment-229881315
So instead of erroring out, detect broken configuration and warn
about it. This should allow existing docker setups to continue
working after kernel upgrade.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 45aebeaf4f ("ovl: Ensure upper filesystem supports d_type")
Cc: <stable@vger.kernel.org> 4.6
The two methods essentially do the same: find the real dentry/inode
belonging to an overlay dentry. The difference is in the usage:
vfs_open() uses ->d_select_inode() and expects the function to perform
copy-up if necessary based on the open flags argument.
file_dentry() uses ->d_real() passing in the overlay dentry as well as the
underlying inode.
vfs_rename() uses ->d_select_inode() but passes zero flags. ->d_real()
with a zero inode would have worked just as well here.
This patch merges the functionality of ->d_select_inode() into ->d_real()
by adding an 'open_flags' argument to the latter.
[Al Viro] Make the signature of d_real() match that of ->d_real() again.
And constify the inode argument, while we are at it.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Pull overlayfs update from Miklos Szeredi:
"The meat of this is a change to use the mounter's credentials for
operations that require elevated privileges (such as whiteout
creation). This fixes behavior under user namespaces as well as being
a nice cleanup"
* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: Do d_type check only if work dir creation was successful
ovl: update documentation
ovl: override creds with the ones from the superblock mounter
d_type check requires successful creation of workdir as iterates
through work dir and expects work dir to be present in it. If that's
not the case, this check will always return d_type not supported even
if underlying filesystem might be supporting it.
So don't do this check if work dir creation failed in previous step.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
In user namespace the whiteout creation fails with -EPERM because the
current process isn't capable(CAP_SYS_ADMIN) when setting xattr.
A simple reproducer:
$ mkdir upper lower work merged lower/dir
$ sudo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merged
$ unshare -m -p -f -U -r bash
Now as root in the user namespace:
\# touch merged/dir/{1,2,3} # this will force a copy up of lower/dir
\# rm -fR merged/*
This ends up failing with -EPERM after the files in dir has been
correctly deleted:
unlinkat(4, "2", 0) = 0
unlinkat(4, "1", 0) = 0
unlinkat(4, "3", 0) = 0
close(4) = 0
unlinkat(AT_FDCWD, "merged/dir", AT_REMOVEDIR) = -1 EPERM (Operation not
permitted)
Interestingly, if you don't place files in merged/dir you can remove it,
meaning if upper/dir does not exist, creating the char device file works
properly in that same location.
This patch uses ovl_sb_creator_cred() to get the cred struct from the
superblock mounter and override the old cred with these new ones so that
the whiteout creation is possible because overlay is wrong in assuming that
the creds it will get with prepare_creds will be in the initial user
namespace. The old cap_raise game is removed in favor of just overriding
the old cred struct.
This patch also drops from ovl_copy_up_one() the following two lines:
override_cred->fsuid = stat->uid;
override_cred->fsgid = stat->gid;
This is because the correct uid and gid are taken directly with the stat
struct and correctly set with ovl_set_attr().
Signed-off-by: Antonio Murdaca <runcom@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Backmerge to resolve a conflict in ovl_lookup_real();
"ovl_lookup_real(): use lookup_one_len_unlocked()" instead,
but it was too late in the cycle to rebase.
Generally permission checking is not necessary when overlayfs looks up a
dentry on one of the underlying layers, since search permission on base
directory was already checked in ovl_permission().
More specifically using lookup_one_len() causes a problem when the lower
directory lacks search permission for a specific user while the upper
directory does have search permission. Since lookups are cached, this
causes inconsistency in behavior: success depends on who did the first
lookup.
So instead use lookup_hash() which doesn't do the permission check.
Reported-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This series fixes bugs in nfs and ext4 due to 4bacc9c923 ("overlayfs:
Make f_path always point to the overlay and f_inode to the underlay").
Regular files opened on overlayfs will result in the file being opened on
the underlying filesystem, while f_path points to the overlayfs
mount/dentry.
This confuses filesystems which get the dentry from struct file and assume
it's theirs.
Add a new helper, file_dentry() [*], to get the filesystem's own dentry
from the file. This checks file->f_path.dentry->d_flags against
DCACHE_OP_REAL, and returns file->f_path.dentry if DCACHE_OP_REAL is not
set (this is the common, non-overlayfs case).
In the uncommon case it will call into overlayfs's ->d_real() to get the
underlying dentry, matching file_inode(file).
The reason we need to check against the inode is that if the file is copied
up while being open, d_real() would return the upper dentry, while the open
file comes from the lower dentry.
[*] If possible, it's better simply to use file_inode() instead.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Tested-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: <stable@vger.kernel.org> # v4.2
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Daniel Axtens <dja@axtens.net>
In some instances xfs has been created with ftype=0 and there if a file
on lower fs is removed, overlay leaves a whiteout in upper fs but that
whiteout does not get filtered out and is visible to overlayfs users.
And reason it does not get filtered out because upper filesystem does
not report file type of whiteout as DT_CHR during iterate_dir().
So it seems to be a requirement that upper filesystem support d_type for
overlayfs to work properly. Do this check during mount and fail if d_type
is not supported.
Suggested-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This patch hides error about missing lowerdir if MS_SILENT is set.
We use mount(NULL, "/", "overlay", MS_SILENT, NULL) for testing support of
overlayfs: syscall returns -ENODEV if it's not supported. Otherwise kernel
automatically loads module and returns -EINVAL because lowerdir is missing.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
After rename file dentry still holds reference to lower dentry from
previous location. This doesn't matter for data access because data comes
from upper dentry. But this stale lower dentry taints dentry at new
location and turns it into non-pure upper. Such file leaves visible
whiteout entry after remove in directory which shouldn't have whiteouts at
all.
Overlayfs already tracks pureness of file location in oe->opaque. This
patch just uses that for detecting actual path type.
Comment from Vivek Goyal's patch:
Here are the details of the problem. Do following.
$ mkdir upper lower work merged upper/dir/
$ touch lower/test
$ sudo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=
work merged
$ mv merged/test merged/dir/
$ rm merged/dir/test
$ ls -l merged/dir/
/usr/bin/ls: cannot access merged/dir/test: No such file or directory
total 0
c????????? ? ? ? ? ? test
Basic problem seems to be that once a file has been unlinked, a whiteout
has been left behind which was not needed and hence it becomes visible.
Whiteout is visible because parent dir is of not type MERGE, hence
od->is_real is set during ovl_dir_open(). And that means ovl_iterate()
passes on iterate handling directly to underlying fs. Underlying fs does
not know/filter whiteouts so it becomes visible to user.
Why did we leave a whiteout to begin with when we should not have.
ovl_do_remove() checks for OVL_TYPE_PURE_UPPER() and does not leave
whiteout if file is pure upper. In this case file is not found to be pure
upper hence whiteout is left.
So why file was not PURE_UPPER in this case? I think because dentry is
still carrying some leftover state which was valid before rename. For
example, od->numlower was set to 1 as it was a lower file. After rename,
this state is not valid anymore as there is no such file in lower.
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Reported-by: Viktor Stanchev <me@viktorstanchev.com>
Suggested-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=109611
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>
This adds missing .d_select_inode into alternative dentry_operations.
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Fixes: 7c03b5d45b ("ovl: allow distributed fs as lower layer")
Fixes: 4bacc9c923 ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Reviewed-by: Nikolay Borisov <kernel@kyup.com>
Tested-by: Nikolay Borisov <kernel@kyup.com>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org> # 4.2+
parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).
Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge third patch-bomb from Andrew Morton:
"I'm pretty much done for -rc1 now:
- the rest of MM, basically
- lib/ updates
- checkpatch, epoll, hfs, fatfs, ptrace, coredump, exit
- cpu_mask simplifications
- kexec, rapidio, MAINTAINERS etc, etc.
- more dma-mapping cleanups/simplifications from hch"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (109 commits)
MAINTAINERS: add/fix git URLs for various subsystems
mm: memcontrol: add "sock" to cgroup2 memory.stat
mm: memcontrol: basic memory statistics in cgroup2 memory controller
mm: memcontrol: do not uncharge old page in page cache replacement
Documentation: cgroup: add memory.swap.{current,max} description
mm: free swap cache aggressively if memcg swap is full
mm: vmscan: do not scan anon pages if memcg swap limit is hit
swap.h: move memcg related stuff to the end of the file
mm: memcontrol: replace mem_cgroup_lruvec_online with mem_cgroup_online
mm: vmscan: pass memcg to get_scan_count()
mm: memcontrol: charge swap to cgroup2
mm: memcontrol: clean up alloc, online, offline, free functions
mm: memcontrol: flatten struct cg_proto
mm: memcontrol: rein in the CONFIG space madness
net: drop tcp_memcontrol.c
mm: memcontrol: introduce CONFIG_MEMCG_LEGACY_KMEM
mm: memcontrol: allow to disable kmem accounting for cgroup2
mm: memcontrol: account "kmem" consumers in cgroup2 memory controller
mm: memcontrol: move kmem accounting code to CONFIG_MEMCG
mm: memcontrol: separate kmem code from legacy tcp accounting code
...
Pull overlayfs updates from Miklos Szeredi:
"This contains several bug fixes and a new mount option
'default_permissions' that allows read-only exported NFS
filesystems to be used as lower layer"
* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: check dentry positiveness in ovl_cleanup_whiteouts()
ovl: setattr: check permissions before copy-up
ovl: root: copy attr
ovl: move super block magic number to magic.h
ovl: use a minimal buffer in ovl_copy_xattr
ovl: allow zero size xattr
ovl: default permissions
i386 allmodconfig:
In file included from fs/overlayfs/super.c:10:0:
fs/overlayfs/super.c: In function 'ovl_fill_super':
include/linux/fs.h:898:36: error: 'PAGE_CACHE_SIZE' undeclared (first use in this function)
#define MAX_LFS_FILESIZE (((loff_t)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1)
^
fs/overlayfs/super.c:939:19: note: in expansion of macro 'MAX_LFS_FILESIZE'
sb->s_maxbytes = MAX_LFS_FILESIZE;
^
include/linux/fs.h:898:36: note: each undeclared identifier is reported only once for each function it appears in
#define MAX_LFS_FILESIZE (((loff_t)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1)
^
fs/overlayfs/super.c:939:19: note: in expansion of macro 'MAX_LFS_FILESIZE'
sb->s_maxbytes = MAX_LFS_FILESIZE;
^
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Without this copy-up of a file can be forced, even without actually being
allowed to do anything on the file.
[Arnd Bergmann] include <linux/pagemap.h> for PAGE_CACHE_SIZE (used by
MAX_LFS_FILESIZE definition).
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>
We copy i_uid and i_gid of underlying inode into overlayfs inode. Except
for the root inode.
Fix this omission.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>
The overlayfs file system is not recognized by programs
like tail because the magic number is not in standard header location.
Move it so that the value will propagate on for the GNU library
and utilities. Needs to go in the fstatfs manual page as well.
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Pull overlayfs bug fixes from Miklos Szeredi:
"This contains fixes for bugs that appeared in earlier kernels (all are
marked for -stable)"
* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: free lower_mnt array in ovl_put_super
ovl: free stack of paths in ovl_fill_super
ovl: fix open in stacked overlay
ovl: fix dentry reference leak
ovl: use O_LARGEFILE in ovl_copy_up()
Add mount option "default_permissions" to alter the way permissions are
calculated.
Without this option and prior to this patch permissions were calculated by
underlying lower or upper filesystem.
With this option the permissions are calculated by overlayfs based on the
file owner, group and mode bits.
This has significance for example when a read-only exported NFS filesystem
is used as a lower layer. In this case the underlying NFS filesystem will
reply with EROFS, in which case all we know is that the filesystem is
read-only. But that's not what we are interested in, we are interested in
whether the access would be allowed if the filesystem wasn't read-only; the
server doesn't tell us that, and would need updating at various levels,
which doesn't seem practicable.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
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>
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
...
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>
