linux-stable.git/fs/fcntl.c, branch linux-3.2.y

fcntl: Don't use ambiguous SIG_POLL si_codes

2017-11-26T13:51:01+00:00

commit d08477aa975e97f1dc64c0ae59cebf98520456ce upstream.

We have a weird and problematic intersection of features that when
they all come together result in ambiguous siginfo values, that
we can not support properly.

- Supporting fcntl(F_SETSIG,...) with arbitrary valid signals.

- Using positive values for POLL_IN, POLL_OUT, POLL_MSG, ..., etc
  that imply they are signal specific si_codes and using the
  aforementioned arbitrary signal to deliver them.

- Supporting injection of arbitrary siginfo values for debugging and
  checkpoint/restore.

The result is that just looking at siginfo si_codes of 1 to 6 are
ambigious.  It could either be a signal specific si_code or it could
be a generic si_code.

For most of the kernel this is a non-issue but for sending signals
with siginfo it is impossible to play back the kernel signals and
get the same result.

Strictly speaking when the si_code was changed from SI_SIGIO to
POLL_IN and friends between 2.2 and 2.4 this functionality was not
ambiguous, as only real time signals were supported.  Before 2.4 was
released the kernel began supporting siginfo with non realtime signals
so they could give details of why the signal was sent.

The result is that if F_SETSIG is set to one of the signals with signal
specific si_codes then user space can not know why the signal was sent.

I grepped through a bunch of userspace programs using debian code
search to get a feel for how often people choose a signal that results
in an ambiguous si_code.  I only found one program doing so and it was
using SIGCHLD to test the F_SETSIG functionality, and did not appear
to be a real world usage.

Therefore the ambiguity does not appears to be a real world problem in
practice.  Remove the ambiguity while introducing the smallest chance
of breakage by changing the si_code to SI_SIGIO when signals with
signal specific si_codes are targeted.

Fixes: v2.3.40 -- Added support for queueing non-rt signals
Fixes: v2.3.21 -- Changed the si_code from SI_SIGIO
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings

userns: rename is_owner_or_cap to inode_owner_or_capable

2011-03-24T02:47:13+00:00

And give it a kernel-doc comment.

[akpm@linux-foundation.org: btrfs changed in linux-next]
Signed-off-by: Serge E. Hallyn 
Cc: "Eric W. Biederman" 
Cc: Daniel Lezcano 
Acked-by: David Howells 
Cc: James Morris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

New kind of open files - "location only".

2011-03-15T06:21:45+00:00

New flag for open(2) - O_PATH.  Semantics:
	* pathname is resolved, but the file itself is _NOT_ opened
as far as filesystem is concerned.
	* almost all operations on the resulting descriptors shall
fail with -EBADF.  Exceptions are:
	1) operations on descriptors themselves (i.e.
		close(), dup(), dup2(), dup3(), fcntl(fd, F_DUPFD),
		fcntl(fd, F_DUPFD_CLOEXEC, ...), fcntl(fd, F_GETFD),
		fcntl(fd, F_SETFD, ...))
	2) fcntl(fd, F_GETFL), for a common non-destructive way to
		check if descriptor is open
	3) "dfd" arguments of ...at(2) syscalls, i.e. the starting
		points of pathname resolution
	* closing such descriptor does *NOT* affect dnotify or
posix locks.
	* permissions are checked as usual along the way to file;
no permission checks are applied to the file itself.  Of course,
giving such thing to syscall will result in permission checks (at
the moment it means checking that starting point of ....at() is
a directory and caller has exec permissions on it).

fget() and fget_light() return NULL on such descriptors; use of
fget_raw() and fget_raw_light() is needed to get them.  That protects
existing code from dealing with those things.

There are two things still missing (they come in the next commits):
one is handling of symlinks (right now we refuse to open them that
way; see the next commit for semantics related to those) and another
is descriptor passing via SCM_RIGHTS datagrams.

Signed-off-by: Al Viro

vfs: sparse: add __FMODE_EXEC

2011-02-03T00:03:19+00:00

FMODE_EXEC is a constant type of fmode_t but was used with normal integer
constants.  This results in following warnings from sparse.  Fix it using
new macro __FMODE_EXEC.

 fs/exec.c:116:58: warning: restricted fmode_t degrades to integer
 fs/exec.c:689:58: warning: restricted fmode_t degrades to integer
 fs/fcntl.c:777:9: warning: restricted fmode_t degrades to integer

Signed-off-by: Namhyung Kim 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fasync: Fix placement of FASYNC flag comment

2010-10-28T01:17:02+00:00

In commit f7347ce4ee7c ("fasync: re-organize fasync entry insertion to
allow it under a spinlock") Arnd took an earlier patch of mine that had
the comment about the FASYNC flag above the wrong function.

When the fasync_add_entry() function was split to introduce the new
fasync_insert_entry() helper function, the code that actually cares
about the FASYNC bit moved to that new helper.

So just move the comment to the right point.

Signed-off-by: Linus Torvalds

fasync: re-organize fasync entry insertion to allow it under a spinlock

2010-10-27T20:06:17+00:00

You currently cannot use "fasync_helper()" in an atomic environment to
insert a new fasync entry, because it will need to allocate the new
"struct fasync_struct".

Yet fcntl_setlease() wants to call this under lock_flocks(), which is in
the process of being converted from the BKL to a spinlock.

In order to fix this, this abstracts out the actual fasync list
insertion and the fasync allocations into functions of their own, and
teaches fs/locks.c to pre-allocate the fasync_struct entry.  That way
the actual list insertion can happen while holding the required
spinlock.

Signed-off-by: Linus Torvalds 
[bfields@redhat.com: rebase on top of my changes to Arnd's patch]
Tested-by: J. Bruce Fields 
Signed-off-by: Arnd Bergmann

vfs: take O_NONBLOCK out of the O_* uniqueness test

2010-09-10T01:57:25+00:00

O_NONBLOCK on parisc has a dual value:

#define O_NONBLOCK	000200004 /* HPUX has separate NDELAY & NONBLOCK */

It is caught by the O_* bits uniqueness check and leads to a parisc
compile error.  The fix would be to take O_NONBLOCK out.

Signed-off-by: Wu Fengguang 
Signed-off-by: James Bottomley 
Cc: Jamie Lokier 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

vfs: O_* bit numbers uniqueness check

2010-08-11T15:59:02+00:00

The O_* bit numbers are defined in 20+ arch/*, and can silently overlap.
Add a compile time check to ensure the uniqueness as suggested by David
Miller.

Signed-off-by: Wu Fengguang 
Cc: David Miller 
Cc: Stephen Rothwell 
Cc: Al Viro 
Cc: Christoph Hellwig 
Cc: Eric Paris 
Cc: Roland Dreier 
Cc: Jamie Lokier 
Cc: Andreas Schwab 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fs/fcntl.c:kill_fasync_rcu() fa_lock must be IRQ-safe

2010-06-29T22:29:32+00:00

Fix a lockdep-splat-causing regression introduced by commit 989a2979205d
("fasync: RCU and fine grained locking").

kill_fasync() can be called from both process and hard-irq context, so
fa_lock must be taken with IRQs disabled.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16230

Reported-by: Sergey Senozhatsky 
Reported-by: Dominik Brodowski 
Tested-by: Dominik Brodowski 
Cc: Maciej Rutecki 
Acked-by: Eric Dumazet 
Cc: Paul E. McKenney 
Cc: Lai Jiangshan 
Cc: "David S. Miller" 
Acked-by: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

fcntl: return -EFAULT if copy_to_user fails

2010-06-04T21:16:28+00:00

copy_to_user() returns the number of bytes remaining, but we want to
return -EFAULT.
	ret = fcntl(fd, F_SETOWN_EX, NULL);
With the original code ret would be 8 here.

V2: Takuya Yoshikawa pointed out a similar issue in f_getown_ex()

Signed-off-by: Dan Carpenter 
Signed-off-by: Al Viro