Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something. And in such cases we end up
with excessive mntput().
Cc: stable@vger.kernel.org # since 2.6.39
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make pathwalk use d_is_reg() rather than S_ISREG() to determine whether to
honour O_TRUNC. Since this occurs after complete_walk(), the dentry type
field cannot change and the inode pointer cannot change as we hold a ref on
the dentry, so this should be safe.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Where we have:
if (!dentry->d_inode || d_is_negative(dentry)) {
type constructions in pathwalk we should be able to eliminate the check of
d_inode and rely solely on the result of d_is_negative() or d_is_positive().
What we do have to take care to do is to read d_inode after calling a
d_is_xxx() typecheck function to get the barriering right.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
just make const char iname[] the last member and compare name->name with
name->iname instead of checking name->separate
We need to make sure that out-of-line name doesn't end up allocated adjacent
to struct filename refering to it; fortunately, it's easy to achieve - just
allocate that struct filename with one byte in ->iname[], so that ->iname[0]
will be inside the same object and thus have an address different from that
of out-of-line name [spotted by Boqun Feng <boqun.feng@gmail.com>]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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>
In order to ensure that filenames are not released before the audit
subsystem is done with the strings there are a number of hacks built
into the fs and audit subsystems around getname() and putname(). To
say these hacks are "ugly" would be kind.
This patch removes the filename hackery in favor of a more
conventional reference count based approach. The diffstat below tells
most of the story; lots of audit/fs specific code is replaced with a
traditional reference count based approach that is easily understood,
even by those not familiar with the audit and/or fs subsystems.
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Enable recording of filenames in getname_kernel() and remove the
kludgy workaround in __audit_inode() now that we have proper filename
logging for kernel users.
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
a) make it accept ERR_PTR() as filename (and return its PTR_ERR() in that case)
b) make it putname() the sucker in the end otherwise
simplifies life for callers...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
There are several areas in the kernel that create temporary filename
objects using the following pattern:
int func(const char *name)
{
struct filename *file = { .name = name };
...
return 0;
}
... which for the most part works okay, but it causes havoc within the
audit subsystem as the filename object does not persist beyond the
lifetime of the function. This patch converts all of these temporary
filename objects into proper filename objects using getname_kernel()
and putname() which ensure that the filename object persists until the
audit subsystem is finished with it.
Also, a special thanks to Al Viro, Guenter Roeck, and Sabrina Dubroca
for helping resolve a difficult kernel panic on boot related to a
use-after-free problem in kern_path_create(); the thread can be seen
at the link below:
* https://lkml.org/lkml/2015/1/20/710
This patch includes code that was either based on, or directly written
by Al in the above thread.
CC: viro@zeniv.linux.org.uk
CC: linux@roeck-us.net
CC: sd@queasysnail.net
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In preparation for expanded use in the kernel, make getname_kernel()
more useful by allowing it to handle any legal filename length.
Thanks to Guenter Roeck for his suggestion to substitute memcpy() for
strlcpy().
CC: linux@roeck-us.net
CC: viro@zeniv.linux.org.uk
CC: linux-fsdevel@vger.kernel.org
Signed-off-by: Paul Moore <pmoore@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull vfs pile #2 from Al Viro:
"Next pile (and there'll be one or two more).
The large piece in this one is getting rid of /proc/*/ns/* weirdness;
among other things, it allows to (finally) make nameidata completely
opaque outside of fs/namei.c, making for easier further cleanups in
there"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
coda_venus_readdir(): use file_inode()
fs/namei.c: fold link_path_walk() call into path_init()
path_init(): don't bother with LOOKUP_PARENT in argument
fs/namei.c: new helper (path_cleanup())
path_init(): store the "base" pointer to file in nameidata itself
make default ->i_fop have ->open() fail with ENXIO
make nameidata completely opaque outside of fs/namei.c
kill proc_ns completely
take the targets of /proc/*/ns/* symlinks to separate fs
bury struct proc_ns in fs/proc
copy address of proc_ns_ops into ns_common
new helpers: ns_alloc_inum/ns_free_inum
make proc_ns_operations work with struct ns_common * instead of void *
switch the rest of proc_ns_operations to working with &...->ns
netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns
make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
common object embedded into various struct ....ns
This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).
The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts). The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.
Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.
Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns. The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).
Related history:
- https://lkml.org/lkml/2006/12/27/123 is an example of someone
realizing that fexecve() is likely to fail in a chroot environment.
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
documenting the /proc requirement of fexecve(3) in its manpage, to
"prevent other people from wasting their time".
- https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
problem where a process that did setuid() could not fexecve()
because it no longer had access to /proc/self/fd; this has since
been fixed.
This patch (of 4):
Add a new execveat(2) system call. execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.
In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers. This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/<fd>" (and
so relies on /proc being mounted).
The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/<fd>"
(for an empty filename) or "/dev/fd/<fd>/<filename>", effectively
reflecting how the executable was found. This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).
Based on patches by Meredydd Luff.
Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All callers of path_init() proceed to do the identical cleanup when
they are done with nameidata. Don't open-code it...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull VFS fixes from Al Viro:
"A bunch of assorted fixes, most of them followups to overlayfs merge"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
ovl: initialize ->is_cursor
Return short read or 0 at end of a raw device, not EIO
isofs: don't bother with ->d_op for normal case
isofs_cmp(): we'll never see a dentry for . or ..
overlayfs: fix lockdep misannotation
ovl: fix check for cursor
overlayfs: barriers for opening upper-layer directory
rcu: Provide counterpart to rcu_dereference() for non-RCU situations
staging: android: logger: Fix log corruption regression
The man page for open(2) indicates that when O_CREAT is specified, the
'mode' argument applies only to future accesses to the file:
Note that this mode applies only to future accesses of the newly
created file; the open() call that creates a read-only file
may well return a read/write file descriptor.
The man page for open(2) implies that 'mode' is treated identically by
O_CREAT and O_TMPFILE.
O_TMPFILE, however, behaves differently:
int fd = open("/tmp", O_TMPFILE | O_RDWR, 0);
assert(fd == -1);
assert(errno == EACCES);
int fd = open("/tmp", O_TMPFILE | O_RDWR, 0600);
assert(fd > 0);
For O_CREAT, do_last() sets acc_mode to MAY_OPEN only:
if (*opened & FILE_CREATED) {
/* Don't check for write permission, don't truncate */
open_flag &= ~O_TRUNC;
will_truncate = false;
acc_mode = MAY_OPEN;
path_to_nameidata(path, nd);
goto finish_open_created;
}
But for O_TMPFILE, do_tmpfile() passes the full op->acc_mode to
may_open().
This patch lines up the behavior of O_TMPFILE with O_CREAT. After the
inode is created, may_open() is called with acc_mode = MAY_OPEN, in
do_tmpfile().
A different, but related glibc bug revealed the discrepancy:
https://sourceware.org/bugzilla/show_bug.cgi?id=17523
The glibc lazily loads the 'mode' argument of open() and openat() using
va_arg() only if O_CREAT is present in 'flags' (to support both the 2
argument and the 3 argument forms of open; same idea for openat()).
However, the glibc ignores the 'mode' argument if O_TMPFILE is in
'flags'.
On x86_64, for open(), it magically works anyway, as 'mode' is in
RDX when entering open(), and is still in RDX on SYSCALL, which is where
the kernel looks for the 3rd argument of a syscall.
But openat() is not quite so lucky: 'mode' is in RCX when entering the
glibc wrapper for openat(), while the kernel looks for the 4th argument
of a syscall in R10. Indeed, the syscall calling convention differs from
the regular calling convention in this respect on x86_64. So the kernel
sees mode = 0 when trying to use glibc openat() with O_TMPFILE, and
fails with EACCES.
Signed-off-by: Eric Rannaud <e@nanocritical.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In an overlay directory that shadows an empty lower directory, say
/mnt/a/empty102, do:
touch /mnt/a/empty102/x
unlink /mnt/a/empty102/x
rmdir /mnt/a/empty102
It's actually harmless, but needs another level of nesting between
I_MUTEX_CHILD and I_MUTEX_NORMAL.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This adds a new RENAME_WHITEOUT flag. This flag makes rename() create a
whiteout of source. The whiteout creation is atomic relative to the
rename.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Whiteout isn't actually a new file type, but is represented as a char
device (Linus's idea) with 0/0 device number.
This has several advantages compared to introducing a new whiteout file
type:
- no userspace API changes (e.g. trivial to make backups of upper layer
filesystem, without losing whiteouts)
- no fs image format changes (you can boot an old kernel/fsck without
whiteout support and things won't break)
- implementation is trivial
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
It's already duplicated in btrfs and about to be used in overlayfs too.
Move the sticky bit check to an inline helper and call the out-of-line
helper only in the unlikly case of the sticky bit being set.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
We need to be able to check inode permissions (but not filesystem implied
permissions) for stackable filesystems. Expose this interface for overlayfs.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Add a new inode operation i_op->dentry_open(). This is for stacked filesystems
that want to return a struct file from a different filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Pull vfs updates from Al Viro:
"The big thing in this pile is Eric's unmount-on-rmdir series; we
finally have everything we need for that. The final piece of prereqs
is delayed mntput() - now filesystem shutdown always happens on
shallow stack.
Other than that, we have several new primitives for iov_iter (Matt
Wilcox, culled from his XIP-related series) pushing the conversion to
->read_iter()/ ->write_iter() a bit more, a bunch of fs/dcache.c
cleanups and fixes (including the external name refcounting, which
gives consistent behaviour of d_move() wrt procfs symlinks for long
and short names alike) and assorted cleanups and fixes all over the
place.
This is just the first pile; there's a lot of stuff from various
people that ought to go in this window. Starting with
unionmount/overlayfs mess... ;-/"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (60 commits)
fs/file_table.c: Update alloc_file() comment
vfs: Deduplicate code shared by xattr system calls operating on paths
reiserfs: remove pointless forward declaration of struct nameidata
don't need that forward declaration of struct nameidata in dcache.h anymore
take dname_external() into fs/dcache.c
let path_init() failures treated the same way as subsequent link_path_walk()
fix misuses of f_count() in ppp and netlink
ncpfs: use list_for_each_entry() for d_subdirs walk
vfs: move getname() from callers to do_mount()
gfs2_atomic_open(): skip lookups on hashed dentry
[infiniband] remove pointless assignments
gadgetfs: saner API for gadgetfs_create_file()
f_fs: saner API for ffs_sb_create_file()
jfs: don't hash direct inode
[s390] remove pointless assignment of ->f_op in vmlogrdr ->open()
ecryptfs: ->f_op is never NULL
android: ->f_op is never NULL
nouveau: __iomem misannotations
missing annotation in fs/file.c
fs: namespace: suppress 'may be used uninitialized' warnings
...
As it is, path_lookupat() and path_mounpoint() might end up leaking struct file
reference in some cases.
Spotted-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull security subsystem updates from James Morris.
Mostly ima, selinux, smack and key handling updates.
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (65 commits)
integrity: do zero padding of the key id
KEYS: output last portion of fingerprint in /proc/keys
KEYS: strip 'id:' from ca_keyid
KEYS: use swapped SKID for performing partial matching
KEYS: Restore partial ID matching functionality for asymmetric keys
X.509: If available, use the raw subjKeyId to form the key description
KEYS: handle error code encoded in pointer
selinux: normalize audit log formatting
selinux: cleanup error reporting in selinux_nlmsg_perm()
KEYS: Check hex2bin()'s return when generating an asymmetric key ID
ima: detect violations for mmaped files
ima: fix race condition on ima_rdwr_violation_check and process_measurement
ima: added ima_policy_flag variable
ima: return an error code from ima_add_boot_aggregate()
ima: provide 'ima_appraise=log' kernel option
ima: move keyring initialization to ima_init()
PKCS#7: Handle PKCS#7 messages that contain no X.509 certs
PKCS#7: Better handling of unsupported crypto
KEYS: Overhaul key identification when searching for asymmetric keys
KEYS: Implement binary asymmetric key ID handling
...
Now that d_invalidate can no longer fail, stop returning a useless
return code. For the few callers that checked the return code update
remove the handling of d_invalidate failure.
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
With the introduction of mount namespaces and bind mounts it became
possible to access files and directories that on some paths are mount
points but are not mount points on other paths. It is very confusing
when rm -rf somedir returns -EBUSY simply because somedir is mounted
somewhere else. With the addition of user namespaces allowing
unprivileged mounts this condition has gone from annoying to allowing
a DOS attack on other users in the system.
The possibility for mischief is removed by updating the vfs to support
rename, unlink and rmdir on a dentry that is a mountpoint and by
lazily unmounting mountpoints on deleted dentries.
In particular this change allows rename, unlink and rmdir system calls
on a dentry without a mountpoint in the current mount namespace to
succeed, and it allows rename, unlink, and rmdir performed on a
distributed filesystem to update the vfs cache even if when there is a
mount in some namespace on the original dentry.
There are two common patterns of maintaining mounts: Mounts on trusted
paths with the parent directory of the mount point and all ancestory
directories up to / owned by root and modifiable only by root
(i.e. /media/xxx, /dev, /dev/pts, /proc, /sys, /sys/fs/cgroup/{cpu,
cpuacct, ...}, /usr, /usr/local). Mounts on unprivileged directories
maintained by fusermount.
In the case of mounts in trusted directories owned by root and
modifiable only by root the current parent directory permissions are
sufficient to ensure a mount point on a trusted path is not removed
or renamed by anyone other than root, even if there is a context
where the there are no mount points to prevent this.
In the case of mounts in directories owned by less privileged users
races with users modifying the path of a mount point are already a
danger. fusermount already uses a combination of chdir,
/proc/<pid>/fd/NNN, and UMOUNT_NOFOLLOW to prevent these races. The
removable of global rename, unlink, and rmdir protection really adds
nothing new to consider only a widening of the attack window, and
fusermount is already safe against unprivileged users modifying the
directory simultaneously.
In principle for perfect userspace programs returning -EBUSY for
unlink, rmdir, and rename of dentires that have mounts in the local
namespace is actually unnecessary. Unfortunately not all userspace
programs are perfect so retaining -EBUSY for unlink, rmdir and rename
of dentries that have mounts in the current mount namespace plays an
important role of maintaining consistency with historical behavior and
making imperfect userspace applications hard to exploit.
v2: Remove spurious old_dentry.
v3: Optimized shrink_submounts_and_drop
Removed unsued afs label
v4: Simplified the changes to check_submounts_and_drop
Do not rename check_submounts_and_drop shrink_submounts_and_drop
Document what why we need atomicity in check_submounts_and_drop
Rely on the parent inode mutex to make d_revalidate and d_invalidate
an atomic unit.
v5: Refcount the mountpoint to detach in case of simultaneous
renames.
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In preparation for allowing mountpoints to be renamed and unlinked
in remote filesystems and in other mount namespaces test if on a dentry
there is a mount in the local mount namespace before allowing it to
be renamed or unlinked.
The primary motivation here are old versions of fusermount unmount
which is not safe if the a path can be renamed or unlinked while it is
verifying the mount is safe to unmount. More recent versions are simpler
and safer by simply using UMOUNT_NOFOLLOW when unmounting a mount
in a directory owned by an arbitrary user.
Miklos Szeredi <miklos@szeredi.hu> reports this is approach is good
enough to remove concerns about new kernels mixed with old versions
of fusermount.
A secondary motivation for restrictions here is that it removing empty
directories that have non-empty mount points on them appears to
violate the rule that rmdir can not remove empty directories. As
Linus Torvalds pointed out this is useful for programs (like git) that
test if a directory is empty with rmdir.
Therefore this patch arranges to enforce the existing mount point
semantics for local mount namespace.
v2: Rewrote the test to be a drop in replacement for d_mountpoint
v3: Use bool instead of int as the return type of is_local_mountpoint
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Commit d6bb3e9075 ("vfs: simplify and shrink stack frame of
link_path_walk()") introduced build problems with GCC versions older
than 4.6 due to the initialisation of a member of an anonymous union in
struct qstr without enclosing braces.
This hits GCC bug 10676 [1] (which was fixed in GCC 4.6 by [2]), and
causes the following build error:
fs/namei.c: In function 'link_path_walk':
fs/namei.c:1778: error: unknown field 'hash_len' specified in initializer
This is worked around by adding explicit braces.
[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676
[2] https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=159206
Fixes: d6bb3e9075 (vfs: simplify and shrink stack frame of link_path_walk())
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-metag@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 9226b5b440 ("vfs: avoid non-forwarding large load after small
store in path lookup") made link_path_walk() always access the
"hash_len" field as a single 64-bit entity, in order to avoid mixed size
accesses to the members.
However, what I didn't notice was that that effectively means that the
whole "struct qstr this" is now basically redundant. We already
explicitly track the "const char *name", and if we just use "u64
hash_len" instead of "long len", there is nothing else left of the
"struct qstr".
We do end up wanting the "struct qstr" if we have a filesystem with a
"d_hash()" function, but that's a rare case, and we might as well then
just squirrell away the name and hash_len at that point.
End result: fewer live variables in the loop, a smaller stack frame, and
better code generation. And we don't need to pass in pointers variables
to helper functions any more, because the return value contains all the
relevant information. So this removes more lines than it adds, and the
source code is clearer too.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs fixes from Al Viro:
"double iput() on failure exit in lustre, racy removal of spliced
dentries from ->s_anon in __d_materialise_dentry() plus a bunch of
assorted RCU pathwalk fixes"
The RCU pathwalk fixes end up fixing a couple of cases where we
incorrectly dropped out of RCU walking, due to incorrect initialization
and testing of the sequence locks in some corner cases. Since dropping
out of RCU walk mode forces the slow locked accesses, those corner cases
slowed down quite dramatically.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
be careful with nd->inode in path_init() and follow_dotdot_rcu()
don't bugger nd->seq on set_root_rcu() from follow_dotdot_rcu()
fix bogus read_seqretry() checks introduced in b37199e
move the call of __d_drop(anon) into __d_materialise_unique(dentry, anon)
[fix] lustre: d_make_root() does iput() on dentry allocation failure
The performance regression that Josef Bacik reported in the pathname
lookup (see commit 99d263d4c5 "vfs: fix bad hashing of dentries") made
me look at performance stability of the dcache code, just to verify that
the problem was actually fixed. That turned up a few other problems in
this area.
There are a few cases where we exit RCU lookup mode and go to the slow
serializing case when we shouldn't, Al has fixed those and they'll come
in with the next VFS pull.
But my performance verification also shows that link_path_walk() turns
out to have a very unfortunate 32-bit store of the length and hash of
the name we look up, followed by a 64-bit read of the combined hash_len
field. That screws up the processor store to load forwarding, causing
an unnecessary hickup in this critical routine.
It's caused by the ugly calling convention for the "hash_name()"
function, and easily fixed by just making hash_name() fill in the whole
'struct qstr' rather than passing it a pointer to just the hash value.
With that, the profile for this function looks much smoother.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
in the former we simply check if dentry is still valid after picking
its ->d_inode; in the latter we fetch ->d_inode in the same places
where we fetch dentry and its ->d_seq, under the same checks.
Cc: stable@vger.kernel.org # 2.6.38+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
return the value instead, and have path_init() do the assignment. Broken by
"vfs: Fix absolute RCU path walk failures due to uninitialized seq number",
which was Cc-stable with 2.6.38+ as destination. This one should go where
it went.
To avoid dummy value returned in case when root is already set (it would do
no harm, actually, since the only caller that doesn't ignore the return value
is guaranteed to have nd->root *not* set, but it's more obvious that way),
lift the check into callers. And do the same to set_root(), to keep them
in sync.
Cc: stable@vger.kernel.org # 2.6.38+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Josef Bacik found a performance regression between 3.2 and 3.10 and
narrowed it down to commit bfcfaa77bd ("vfs: use 'unsigned long'
accesses for dcache name comparison and hashing"). He reports:
"The test case is essentially
for (i = 0; i < 1000000; i++)
mkdir("a$i");
On xfs on a fio card this goes at about 20k dir/sec with 3.2, and 12k
dir/sec with 3.10. This is because we spend waaaaay more time in
__d_lookup on 3.10 than in 3.2.
The new hashing function for strings is suboptimal for <
sizeof(unsigned long) string names (and hell even > sizeof(unsigned
long) string names that I've tested). I broke out the old hashing
function and the new one into a userspace helper to get real numbers
and this is what I'm getting:
Old hash table had 1000000 entries, 0 dupes, 0 max dupes
New hash table had 12628 entries, 987372 dupes, 900 max dupes
We had 11400 buckets with a p50 of 30 dupes, p90 of 240 dupes, p99 of 567 dupes for the new hash
My test does the hash, and then does the d_hash into a integer pointer
array the same size as the dentry hash table on my system, and then
just increments the value at the address we got to see how many
entries we overlap with.
As you can see the old hash function ended up with all 1 million
entries in their own bucket, whereas the new one they are only
distributed among ~12.5k buckets, which is why we're using so much
more CPU in __d_lookup".
The reason for this hash regression is two-fold:
- On 64-bit architectures the down-mixing of the original 64-bit
word-at-a-time hash into the final 32-bit hash value is very
simplistic and suboptimal, and just adds the two 32-bit parts
together.
In particular, because there is no bit shuffling and the mixing
boundary is also a byte boundary, similar character patterns in the
low and high word easily end up just canceling each other out.
- the old byte-at-a-time hash mixed each byte into the final hash as it
hashed the path component name, resulting in the low bits of the hash
generally being a good source of hash data. That is not true for the
word-at-a-time case, and the hash data is distributed among all the
bits.
The fix is the same in both cases: do a better job of mixing the bits up
and using as much of the hash data as possible. We already have the
"hash_32|64()" functions to do that.
Reported-by: Josef Bacik <jbacik@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Empty files and missing xattrs do not guarantee that a file was
just created. This patch passes FILE_CREATED flag to IMA to
reliably identify new files.
Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> 3.14+
Looks like the directory loop check is actually done in renameat?
Whatever, leave this out rather than trying to keep it up to date with
the code.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
In REF-walk mode, ->d_manage can return -EISDIR to indicate
that the dentry is not really a mount trap (or even a mount point)
and that any mounts or any DCACHE_NEED_AUTOMOUNT flag should be
ignored.
RCU-walk mode doesn't currently support this, so if there is a dentry
with DCACHE_NEED_AUTOMOUNT set but which shouldn't be a mount-trap,
lookup_fast() will always drop in REF-walk mode.
With this patch, an -EISDIR from ->d_manage will always cause mounts
and automounts to be ignored, both in REF-walk and RCU-walk.
Bug-fixed-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Al Viro