linux.git/fs/proc/base.c, branch v2.6.18

Don't allow chmod() on the /proc// files

2006-07-15T19:26:45+00:00

This just turns off chmod() on the /proc// files, since there is no
good reason to allow it, and had we disallowed it originally, the nasty
/proc race exploit wouldn't have been possible.

The other patches already fixed the problem chmod() could cause, so this
is really just some final mop-up..

This particular version is based off a patch by Eugene and Marcel which
had much better naming than my original equivalent one.

Signed-off-by: Eugene Teo 
Signed-off-by: Marcel Holtmann 
Signed-off-by: Linus Torvalds

Relax /proc fix a bit

2006-07-15T04:48:03+00:00

Clearign all of i_mode was a bit draconian. We only really care about
S_ISUID/ISGID, after all.

Signed-off-by: Linus Torvalds

Fix nasty /proc vulnerability

2006-07-14T23:51:34+00:00

We have a bad interaction with both the kernel and user space being able
to change some of the /proc file status.  This fixes the most obvious
part of it, but I expect we'll also make it harder for users to modify
even their "own" files in /proc.

Signed-off-by: Linus Torvalds

Remove obsolete #include

2006-06-30T17:25:36+00:00

Signed-off-by: Jörn Engel 
Signed-off-by: Adrian Bunk

[PATCH] SELinux: Add sockcreate node to procattr API

2006-06-26T16:58:26+00:00

Below is a patch to add a new /proc/self/attr/sockcreate A process may write a
context into this interface and all subsequent sockets created will be labeled
with that context.  This is the same idea as the fscreate interface where a
process can specify the label of a file about to be created.  At this time one
envisioned user of this will be xinetd.  It will be able to better label
sockets for the actual services.  At this time all sockets take the label of
the creating process, so all xinitd sockets would just be labeled the same.

I tested this by creating a tcp sender and listener.  The sender was able to
write to this new proc file and then create sockets with the specified label.
I am able to be sure the new label was used since the avc denial messages
kicked out by the kernel included both the new security permission
setsockcreate and all the socket denials were for the new label, not the label
of the running process.

Signed-off-by: Eric Paris 
Signed-off-by: James Morris 
Cc: Chris Wright 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cleanup next_tid()

2006-06-26T16:58:26+00:00

Try to make next_tid() a bit more readable and deletes unnecessary
"pid_alive(pos)" check.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] simplify/fix first_tid()

2006-06-26T16:58:26+00:00

first_tid:

	/* If nr exceeds the number of threads there is nothing todo */
	if (nr) {
		if (nr >= get_nr_threads(leader))
			goto done;
	}

This is not reliable: sub-threads can exit after this check, so the
'for' loop below can overlap and proc_task_readdir() can return an
already filldir'ed dirents.

	for (; pos && pid_alive(pos); pos = next_thread(pos)) {
		if (--nr > 0)
			continue;

Off-by-one error, will return 'leader' when nr == 1.

This patch tries to fix these problems and simplify the code.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] proc: Remove tasklist_lock from proc_task_readdir.

2006-06-26T16:58:26+00:00

This is just like my previous removal of tasklist_lock from first_tgid, and
next_tgid.  It simply had to wait until it was rcu safe to walk the thread
list.

This should be the last instance of the tasklist_lock in proc.  So user
processes should not be able to influence the tasklist lock hold times.

Signed-off-by: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] proc: Cleanup proc_fd_access_allowed

2006-06-26T16:58:26+00:00

In process of getting proc_fd_access_allowed to work it has developed a few
warts.  In particular the special case that always allows introspection and
the special case to allow inspection of kernel threads.

The special case for introspection is needed for /proc/self/mem.

The special case for kernel threads really should be overridable
by security modules.

So consolidate these checks into ptrace.c:may_attach().

The check to always allow introspection is trivial.

The check to allow access to kernel threads, and zombies is a little
trickier.  mem_read and mem_write already verify an mm exists so it isn't
needed twice.  proc_fd_access_allowed only doesn't want a check to verify
task->mm exits, s it prevents all access to kernel threads.  So just move
the task->mm check into ptrace_attach where it is needed for practical
reasons.

I did a quick audit and none of the security modules in the kernel seem to
care if they are passed a task without an mm into security_ptrace.  So the
above move should be safe and it allows security modules to come up with
more restrictive policy.

Signed-off-by: Eric W. Biederman 
Cc: Stephen Smalley 
Cc: Chris Wright 
Cc: James Morris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] proc: Use sane permission checks on the /proc//fd/ symlinks

2006-06-26T16:58:26+00:00

Since 2.2 we have been doing a chroot check to see if it is appropriate to
return a read or follow one of these magic symlinks.  The chroot check was
asking a question about the visibility of files to the calling process and
it was actually checking the destination process, and not the files
themselves.  That test was clearly bogus.

In my first pass through I simply fixed the test to check the visibility of
the files themselves.  That naive approach to fixing the permissions was
too strict and resulted in cases where a task could not even see all of
it's file descriptors.

What has disturbed me about relaxing this check is that file descriptors
are per-process private things, and they are occasionaly used a user space
capability tokens.  Looking a little farther into the symlink path on /proc
I did find userid checks and a check for capability (CAP_DAC_OVERRIDE) so
there were permissions checking this.

But I was still concerned about privacy.  Besides /proc there is only one
other way to find out this kind of information, and that is ptrace.  ptrace
has been around for a long time and it has a well established security
model.

So after thinking about it I finally realized that the permission checks
that make sense are the permission checks applied to ptrace_attach.  The
checks are simple per process, and won't cause nasty surprises for people
coming from less capable unices.

Unfortunately there is one case that the current ptrace_attach test does
not cover: Zombies and kernel threads.  Single stepping those kinds of
processes is impossible.  Being able to see which file descriptors are open
on these tasks is important to lsof, fuser and friends.  So for these
special processes I made the rule you can't find out unless you have
CAP_SYS_PTRACE.

These proc permission checks should now conform to the principle of least
surprise.  As well as using much less code to implement :)

Signed-off-by: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds