linux.git/fs/namei.c, branch v3.11

vfs: make the dentry cache use the lockref infrastructure

2013-08-29T01:24:59+00:00

This just replaces the dentry count/lock combination with the lockref
structure that contains both a count and a spinlock, and does the
mechanical conversion to use the lockref infrastructure.

There are no semantic changes here, it's purely syntactic.  The
reference lockref implementation uses the spinlock exactly the same way
that the old dcache code did, and the bulk of this patch is just
expanding the internal "d_count" use in the dcache code to use
"d_lockref.count" instead.

This is purely preparation for the real change to make the reference
count updates be lockless during the 3.12 merge window.

[ As with the previous commit, this is a rewritten version of a concept
  originally from Waiman, so credit goes to him, blame for any errors
  goes to me.

  Waiman's patch had some semantic differences for taking advantage of
  the lockless update in dget_parent(), while this patch is
  intentionally a pure search-and-replace change with no semantic
  changes.     - Linus ]

Signed-off-by: Waiman Long 
Signed-off-by: Linus Torvalds

Revert "fs: Allow unprivileged linkat(..., AT_EMPTY_PATH) aka flink"

2013-08-28T16:18:05+00:00

This reverts commit bb2314b47996491bbc5add73633905c3120b6268.

It wasn't necessarily wrong per se, but we're still busily discussing
the exact details of this all, so I'm going to revert it for now.

It's true that you can already do flink() through /proc and that flink()
isn't new.  But as Brad Spengler points out, some secure environments do
not mount proc, and flink adds a new interface that can avoid path
lookup of the source for those kinds of environments.

We may re-do this (and even mark it for stable backporting back in 3.11
and possibly earlier) once the whole discussion about the interface is done.

Cc: Andy Lutomirski 
Cc: Al Viro 
Cc: Oleg Nesterov 
Cc: Brad Spengler 
Signed-off-by: Linus Torvalds

fs: Allow unprivileged linkat(..., AT_EMPTY_PATH) aka flink

2013-08-05T14:24:11+00:00

Every now and then someone proposes a new flink syscall, and this spawns
a long discussion of whether it would be a security problem.  I think
that this is missing the point: flink is *already* allowed without
privilege as long as /proc is mounted -- it's called AT_SYMLINK_FOLLOW.

Now that O_TMPFILE is here, the ability to create a file with O_TMPFILE,
write it, and link it in is very convenient.  The only problem is that
it requires that /proc be mounted so that you can do:

linkat(AT_FDCWD, "/proc/self/fd/", dfd, path, AT_SYMLINK_NOFOLLOW)

This sucks -- it's much nicer to do:

linkat(tmpfd, "", dfd, path, AT_EMPTY_PATH)

Let's allow it.

If this turns out to be excessively scary, it we could instead require
that the inode in question be I_LINKABLE, but this seems pointless given
the /proc situation

Signed-off-by: Andy Lutomirski 
Signed-off-by: Al Viro

Safer ABI for O_TMPFILE

2013-07-13T09:26:37+00:00

[suggested by Rasmus Villemoes] make O_DIRECTORY | O_RDWR part of O_TMPFILE;
that will fail on old kernels in a lot more cases than what I came up with.
And make sure O_CREAT doesn't get there...

Signed-off-by: Al Viro

Don't pass inode to ->d_hash() and ->d_compare()

2013-06-29T08:57:36+00:00

Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry->d_sb).
A few cases that want more are actually safe with dentry->d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.

Signed-off-by: Linus Torvalds 
Signed-off-by: Al Viro

allow the temp files created by open() to be linked to

2013-06-29T08:57:11+00:00

O_TMPFILE | O_CREAT => linkat() with AT_SYMLINK_FOLLOW and /proc/self/fd/
as oldpath (i.e. flink()) will create a link
O_TMPFILE | O_CREAT | O_EXCL => ENOENT on attempt to link those guys

Signed-off-by: Al Viro

[O_TMPFILE] it's still short a few helpers, but infrastructure should be OK now...

2013-06-29T08:57:10+00:00

Signed-off-by: Al Viro

allow build_open_flags() to return an error

2013-06-29T08:57:09+00:00

Signed-off-by: Al Viro

do_last(): fix missing checks for LAST_BIND case

2013-06-29T08:57:07+00:00

/proc/self/cwd with O_CREAT should fail with EISDIR.  /proc/self/exe, OTOH,
should fail with ENOTDIR when opened with O_DIRECTORY.

Signed-off-by: Al Viro

use can_lookup() instead of direct checks of ->i_op->lookup

2013-06-15T01:41:45+00:00

a couple of places got missed back when Linus has introduced that one...

Signed-off-by: Al Viro