This is more prep-work for the upcoming pty changes. Still just code
cleanup with no actual semantic changes.
This removes a bunch pointless complexity by just having the slave pty
side remember the dentry associated with the devpts slave rather than
the inode. That allows us to remove all the "look up the dentry" code
for when we want to remove it again.
Together with moving the tty pointer from "inode->i_private" to
"dentry->d_fsdata" and getting rid of pointless inode locking, this
removes about 30 lines of code. Not only is the end result smaller,
it's simpler and easier to understand.
The old code, for example, depended on the d_find_alias() to not just
find the dentry, but also to check that it is still hashed, which in
turn validated the tty pointer in the inode.
That is a _very_ roundabout way to say "invalidate the cached tty
pointer when the dentry is removed".
The new code just does
dentry->d_fsdata = NULL;
in devpts_pty_kill() instead, invalidating the tty pointer rather more
directly and obviously. Don't do something complex and subtle when the
obvious straightforward approach will do.
The rest of the patch (ie apart from code deletion and the above tty
pointer clearing) is just switching the calling convention to pass the
dentry or file pointer around instead of the inode.
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Jann Horn <jann@thejh.net>
Cc: Greg KH <greg@kroah.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This gets rid of the horrible notion of having that
struct inode *ptmx_inode
be the linchpin of the interface between the pty code and devpts.
By de-emphasizing the ptmx inode, a lot of things actually get cleaner,
and we will have a much saner way forward. In particular, this will
allow us to associate with any particular devpts instance at open-time,
and not be artificially tied to one particular ptmx inode.
The patch itself is actually fairly straightforward, and apart from some
locking and return path cleanups it's pretty mechanical:
- the interfaces that devpts exposes all take "struct pts_fs_info *"
instead of "struct inode *ptmx_inode" now.
NOTE! The "struct pts_fs_info" thing is a completely opaque structure
as far as the pty driver is concerned: it's still declared entirely
internally to devpts. So the pty code can't actually access it in any
way, just pass it as a "cookie" to the devpts code.
- the "look up the pts fs info" is now a single clear operation, that
also does the reference count increment on the pts superblock.
So "devpts_add/del_ref()" is gone, and replaced by a "lookup and get
ref" operation (devpts_get_ref(inode)), along with a "put ref" op
(devpts_put_ref()).
- the pty master "tty->driver_data" field now contains the pts_fs_info,
not the ptmx inode.
- because we don't care about the ptmx inode any more as some kind of
base index, the ref counting can now drop the inode games - it just
gets the ref on the superblock.
- the pts_fs_info now has a back-pointer to the super_block. That's so
that we can easily look up the information we actually need. Although
quite often, the pts fs info was actually all we wanted, and not having
to look it up based on some magical inode makes things more
straightforward.
In particular, now that "devpts_get_ref(inode)" operation should really
be the *only* place we need to look up what devpts instance we're
associated with, and we do it exactly once, at ptmx_open() time.
The other side of this is that one ptmx node could now be associated
with multiple different devpts instances - you could have a single
/dev/ptmx node, and then have multiple mount namespaces with their own
instances of devpts mounted on /dev/pts/. And that's all perfectly sane
in a model where we just look up the pts instance at open time.
This will eventually allow us to get rid of our odd single-vs-multiple
pts instance model, but this patch in itself changes no semantics, only
an internal binding model.
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Peter Anvin <hpa@zytor.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Jann Horn <jann@thejh.net>
Cc: Greg KH <greg@kroah.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Considering current pty code and multiple devpts instances, it's possible
to umount a devpts file system while a program still has /dev/tty opened
pointing to a previosuly closed pty pair in that instance. In the case all
ptmx and pts/N files are closed, umount can be done. If the program closes
/dev/tty after umount is done, devpts_kill_index will use now an invalid
super_block, which was already destroyed in the umount operation after
running ->kill_sb. This is another "use after free" type of issue, but now
related to the allocated super_block instance.
To avoid the problem (warning at ida_remove and potential crashes) for
this specific case, I added two functions in devpts which grabs additional
references to the super_block, which pty code now uses so it makes sure
the super block structure is still valid until pty shutdown is done.
I also moved the additional inode references to the same functions, which
also covered similar case with inode being freed before /dev/tty final
close/shutdown.
Signed-off-by: Herton R. Krzesinski <herton@redhat.com>
Cc: stable@vger.kernel.org # 2.6.29+
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This change fixes a bug for a corner case where we have the the last
release from a pty master/slave coming from a previously opened /dev/tty
file. When this happens, the tty->driver_data can be stale, due to all
ptmx or pts/N files having already been closed before (and thus the inode
related to these files, which tty->driver_data points to, being already
freed/destroyed).
The fix here is to keep a reference on the opened master ptmx inode.
We maintain the inode referenced until the final pty_unix98_shutdown,
and only pass this inode to devpts_kill_index.
Signed-off-by: Herton R. Krzesinski <herton@redhat.com>
Cc: <stable@vger.kernel.org> # 2.6.29+
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Expressions of the form "tty->termios.c_*flag & FLAG"
are more clearly expressed with the termios flags macros,
I_FLAG(), C_FLAG(), O_FLAG(), and L_FLAG().
Convert treewide.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty core invokes the optional driver shutdown() just before
the optional driver remove() (shutdown() has access to the termios
and remove() does not). Because pty drivers must prevent the default
remove() action, the Unix98 pty drivers define a dummy remove() function.
Instead, release the slave index in the remove() method and delete the
optional shutdown() method.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tty_init_termios() never returns an error; re-declare as void. Remove
unnecessary error handling from callers. Remove extern declarations
of tty_free_termios() and free_tty_struct() and re-declare in file
scope.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
release_tty() leaks the ldisc instance when called directly (rather
than when releasing the file descriptor from tty_release()).
Since tty_ldisc_release() clears tty->ldisc, releasing the ldisc
instance at tty teardown if tty->ldisc is non-null is not in danger
of double-releasing the ldisc.
Remove deinitialize_tty_struct() now that free_tty_struct() always
performs the tty_ldisc_deinit().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that tty_debug() macro uses pr_debug(), the function name can
be printed when using dynamic debug; printing the function name within
the format string is redundant.
Remove the __func__ parameter and print specifier from the format string.
Add context to messages for when the function name is not printed by
dynamic debug, or when dynamic debug is not enabled.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The Kconfig currently controlling compilation of this code is:
drivers/tty/Kconfig:config LEGACY_PTYS
drivers/tty/Kconfig: bool "Legacy (BSD) PTY support"
...and:
drivers/tty/Kconfig:config UNIX98_PTYS
drivers/tty/Kconfig: bool "Unix98 PTY support" if EXPERT
combined with this:
obj-$(CONFIG_LEGACY_PTYS) += pty.o
obj-$(CONFIG_UNIX98_PTYS) += pty.o
...meaning that it currently is not being built as a module by anyone.
Lets remove the traces of modularity we can so that when reading the
driver there is less doubt it is builtin-only.
Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit.
We don't delete the module.h include since other parts of the file are
using content from there.
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Opens of /dev/ptmx don't use tty_open() so debug messages are
not printed for those opens; print a debug message with the
open count (which must always be 1) if TTY_DEBUG_HANGUP is defined.
NB: Each tty core source file undefs support for debug messages.
The relevant source file must be patched/edited to enable these
messages.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A read() from a pty master may mistakenly indicate EOF (errno == -EIO)
after the pty slave has closed, even though input data remains to be read.
For example,
pty slave | input worker | pty master
| |
| | n_tty_read()
pty_write() | | input avail? no
add data | | sleep
schedule worker --->| | .
|---> flush_to_ldisc() | .
pty_close() | fill read buffer | .
wait for worker | wakeup reader --->| .
| read buffer full? |---> input avail ? yes
|<--- yes - exit worker | copy 4096 bytes to user
TTY_OTHER_CLOSED <---| |<--- kick worker
| |
**** New read() before worker starts ****
| | n_tty_read()
| | input avail? no
| | TTY_OTHER_CLOSED? yes
| | return -EIO
Several conditions are required to trigger this race:
1. the ldisc read buffer must become full so the input worker exits
2. the read() count parameter must be >= 4096 so the ldisc read buffer
is empty
3. the subsequent read() occurs before the kicked worker has processed
more input
However, the underlying cause of the race is that data is pipelined, while
tty state is not; ie., data already written by the pty slave end is not
yet visible to the pty master end, but state changes by the pty slave end
are visible to the pty master end immediately.
Pipeline the TTY_OTHER_CLOSED state through input worker to the reader.
1. Introduce TTY_OTHER_DONE which is set by the input worker when
TTY_OTHER_CLOSED is set and either the input buffers are flushed or
input processing has completed. Readers/polls are woken when
TTY_OTHER_DONE is set.
2. Reader/poll checks TTY_OTHER_DONE instead of TTY_OTHER_CLOSED.
3. A new input worker is started from pty_close() after setting
TTY_OTHER_CLOSED, which ensures the TTY_OTHER_DONE state will be
set if the last input worker is already finished (or just about to
exit).
Remove tty_flush_to_ldisc(); no in-tree callers.
Fixes: 52bce7f8d4 ("pty, n_tty: Simplify input processing on final close")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=96311
BugLink: http://bugs.launchpad.net/bugs/1429756
Cc: <stable@vger.kernel.org> # 3.19+
Reported-by: Andy Whitcroft <apw@canonical.com>
Reported-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
BRKINT and ISIG requires input and output flush when a signal char
is received. However, the order of operations is significant since
parallel i/o may be ongoing.
Merge the signal handling for BRKINT with ISIG handling.
Process the signal first. This ensures any ongoing i/o is aborted;
without this, a waiting writer may continue writing after the flush
occurs and after the signal char has been echoed.
Write lock the termios_rwsem, which excludes parallel writers from
pushing new i/o until after the output buffers are flushed; claiming
the write lock is necessary anyway to exclude parallel readers while
the read buffer is flushed.
Subclass the termios_rwsem for ptys since the slave pty performing
the flush may appear to reorder the termios_rwsem->tty buffer lock
lock order; adding annotation clarifies that
slave tty_buffer lock-> slave termios_rwsem -> master tty_buffer lock
is a valid lock order.
Flush the echo buffer. In this context, the echo buffer is 'output'.
Otherwise, the output will appear discontinuous because the output buffer
was cleared which contains older output than the echo buffer.
Open-code the read buffer flush since the input worker does not need
kicking (this is the input worker).
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The pty driver does not clear its write buffer when commanded.
This is to avoid an apparent deadlock between parallel flushes from
both pty ends; specifically when handling either BRK or INTR input.
However, parallel flushes from this source is not possible since
the pty master can never be set to BRKINT or ISIG. Parallel flushes
from other sources are possible but these do not threaten deadlocks.
Annotate the tty buffer mutex for lockdep to represent the nested
tty_buffer locking which occurs when the pty slave is processing input
(its buffer mutex held) and receives INTR or BRK and acquires the
linked tty buffer mutex via tty_buffer_flush().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The pty_space() computation is broken; the space already consumed
in the tty buffer is not accounted for.
Use tty_buffer_set_limit(), which enforces the limit automatically.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 26df6d1340 ("tty: Add EXTPROC support for LINEMODE")
allows a process which has opened a pty master to send _any_ signal
to the process group of the pty slave. Although potentially
exploitable by a malicious program running a setuid program on
a pty slave, it's unknown if this exploit currently exists.
Limit to signals actually used.
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Howard Chu <hyc@symas.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: <stable@vger.kernel.org> # 2.6.36+
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When releasing one end of a pty pair, that end may just have written
to the other, which the input processing worker, flush_to_ldisc(), is
still working on but has not completed the copy to the other end's
read buffer. So input may not appear to be available to a waiting
reader but yet TTY_OTHER_CLOSED is now observed. The n_tty line
discipline has worked around this by waiting for input processing
to complete and then re-checking if input is available before
exiting with -EIO.
Since the tty/ldisc lock reordering, the wait for input processing
to complete can now occur during final close before setting
TTY_OTHER_CLOSED. In this way, a waiting reader is guaranteed to
see input available (if any) before observing TTY_OTHER_CLOSED.
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With the revised tty lock order and lockdep annotation, claiming
the pty slave lock is now safe while still holding the pty master lock.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Eliminate the requirement of specifying the tty lock nesting at
lock time; instead, set the lock subclass for slave ptys at pty
install (normal ttys and master ptys use subclass 0).
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Opening the slave BSD pty first already returns -EIO from the slave
pty_open(), which in turn causes the newly installed tty pair to be
released before returning from tty_open(). However, this can also
cause a parallel master BSD pty open to fail because the pty pair
destruction may already been taking place in tty_release().
Failing at driver->install() if the slave pty is opened first ensures
that a pty master open cannot fail, because the driver tables will
not have been updated so tty_driver_lookup_tty() won't find the
master pty (and attempt to "re-open" it).
In turn, this guarantees that any tty with a tty->count == 0 is
in final close (rather than never opened).
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Updates to the packet mode enable require holding the ctrl_lock;
the serialization prevents corruption of adjacent fields.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Because pty_set_pktmode() does not claim the slave's ctrl_lock
to clear ->ctrl_status (to avoid unnecessary lock nesting),
pty_set_pktmode() may accidentally erase new ->ctrl_status updates.
For example,
CPU 0 | CPU 1
pty_set_pktmode() | pty_start()
spin_lock(master's ctrl_lock) |
tty->packet = 1 |
| if (tty->link->packet)
| spin_lock(slave's ctrl_lock)
| tty->ctrl_status = TIOCPKT_START
tty->link->ctrl_status = 0 |
Ensure the clear of ->ctrl_status occurs before packet mode is set
(and observable on another cpu).
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The slave's ctrl_lock serializes updates to the ctrl_status field
only, whereas the master's ctrl_lock serializes updates to the
packet mode enable (ie., the master does not have ctrl_status and
the slave does not have packet mode). Thus, claiming the slave's
ctrl_lock to access ->packet is useless.
Unlocked reads of ->packet are already smp-safe.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Interrupts are enabled in the n_tty_read() loop, ioctl(TIOCPKT)
and pty driver flush_buffer() routine; no need to save and restore
local interrupt state.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The tty driver's set_termios() method is called with interrupts
enabled; there is no need to save and restore the local interrupt state.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Packet mode is unique to the pty driver; move the packet mode state
change code from the generic tty ioctl handler to the pty driver.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The pty master's termios should never be set; currently, all code
paths which call the driver's set_termios() method ensure that the
pty slave's termios is being set.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When a master pty is set to packet mode, flow control changes to
the slave pty cause notifications to the master pty via reads and
polls. However, these tests are occurring for all ttys, not
just ptys.
Implement flow control packet mode notifications in the pty driver.
Only the slave side implements the flow control handlers since
packet mode is asymmetric; the master pty receives notifications
for slave-side changes, but not vice versa.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In 2c964a2f "drivers: tty: Merge alloc_tty_struct and
initialize_tty_struct", I messed up the refactorization of
pty_common_install, causing use-after-free and NULL pointer derefs on
various error paths. This should fix it.
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The two functions alloc_tty_struct and initialize_tty_struct are
always called together. Merge them into alloc_tty_struct, updating its
prototype and the only two callers of these functions.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acquiring the write_wait queue spin lock now accounts for the largest
slice of cpu time on the tty write path. Two factors contribute to
this situation; a overly-pessimistic line discipline write loop which
_always_ sets up a wait loop even if i/o will immediately succeed, and
on ptys, a wakeup storm from reads and writes.
Writer wakeup does not need to be performed by the pty driver.
Firstly, since the actual i/o is performed within the write, the
line discipline write loop will continue while space remains in
the flip buffers. Secondly, when space becomes avail in the
line discipline receive buffer (and thus also in the flip buffers),
the pty unthrottle re-wakes the writer (non-flow-controlled line
disciplines unconditionally unthrottle the driver when data is
received). Thus, existing in-kernel i/o is guaranteed to advance.
Finally, writer wakeup occurs at the conclusion of the line discipline
write (in tty_write_unlock()). This guarantees that any user-space write
waiters are woken to continue additional i/o.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Lockless flip buffers require atomically updating the bytes-in-use
watermark.
The pty driver also peeks at the watermark value to limit
memory consumption to a much lower value than the default; query
the watermark with new fn, tty_buffer_space_avail().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit 699390354d
('pty: Ignore slave pty close() if never successfully opened')
introduced a bug with ptys whereby a write() in parallel with an
open() on an existing pty could mistakenly indicate an I/O error.
Only indicate an I/O error if the condition on open() actually exists.
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Tested-by: Mikael Pettersson <mikpe@it.uu.se>
Cc: stable <stable@vger.kernel.org> # 3.9
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We first tried to avoid updating atime/mtime entirely (commit
b0de59b5733d: "TTY: do not update atime/mtime on read/write"), and then
limited it to only update it occasionally (commit 37b7f3c76595: "TTY:
fix atime/mtime regression"), but it turns out that this was both
insufficient and overkill.
It was insufficient because we let people attach to the shared ptmx node
to see activity without even reading atime/mtime, and it was overkill
because the "only once a minute" means that you can't really tell an
idle person from an active one with 'w'.
So this tries to fix the problem properly. It marks the shared ptmx
node as un-notifiable, and it lowers the "only once a minute" to a few
seconds instead - still long enough that you can't time individual
keystrokes, but short enough that you can tell whether somebody is
active or not.
Reported-by: Simon Kirby <sim@hostway.ca>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When CONFIG_UNIX98_PTYS is unset, we see this warning in pty:
drivers/tty/pty.c:409:13: warning: ‘pty_unix98_shutdown’ defined but not used
Fix that by moving the function to a section which depends on that
config.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Toralf Foerster <toralf.foerster@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
port->itty has already been reset by release_tty() before
pty_cleanup() is called.
Call stack:
release_tty()
tty_kref_put()
queue_release_one_tty()
release_one_tty() : workqueue
tty->ops->cleanup()
pty_cleanup()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Multiple slave pty opens may be performed in parallel with the
master open. Of course, all the slave opens will fail because the
master pty is still locked but during this time the slave pty
count will be artificially greater than 1. This is should not
cause the master pty open to fail.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If the master and slave ptys are opened in parallel, the slave open
fails because the pty is still locked. This is as designed.
However, pty_close() is still called for the slave pty which sets
TTY_OTHER_CLOSED in the master pty. This can cause the master open
to fail as well.
Use a common pattern in other tty drivers by setting TTY_IO_ERROR
until the open is successful and only closing the pty if not set.
Note: the master pty always closes regardless of whether the open
was successful, so that proper cleanup can occur.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Commit bbb63c514a (drivers:tty:fix up
ENOIOCTLCMD error handling) changed the default return value from tty
ioctl to be ENOTTY and not EINVAL. This is appropriate.
But in case of TIOCGPTN for the old BSD ptys glibc started failing
because it expects EINVAL to be returned. Only then it continues to
obtain the pts name the other way around.
So fix this case by explicit return of EINVAL in this case.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Florian Westphal <fw@strlen.de>
Cc: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@vger.kernel.org> # 3.7+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now that login from util-linux is forced to drop all references to a
TTY which it wants to hangup (to reach reference count 1) we are
seeing issues with telnet. When login closes its last reference to the
slave PTY, it also resets packet mode on the *master* side. And we
have a race here.
What telnet does is fork+exec of `login'. Then there are two
scenarios:
* `login' closes the slave TTY and resets thus master's packet mode,
but even now telnet properly sets the mode, or
* `telnetd' sets packet mode on the master, `login' closes the slave
TTY and resets master's packet mode.
The former case is OK. However the latter happens in much more cases,
by the order of magnitude to be precise. So when one tries to login to
such a messed telnet setup, they see the following:
inux login:
ogin incorrect
Note the missing first letters -- telnet thinks it is still in the
packet mode, so when it receives "linux login" from `login', it
considers "l" as the type of the packet and strips it.
SuS does not mention how the implementation should behave. Both BSDs I
checked (Free and Net) do not reset the flag upon the last close.
By this I am resurrecting an old bug, see References. We are hitting
it regularly now, i.e. with updated util-linux, ergo login.
Here, I am changing a behavior introduced back in 2.1 times. It would
better have a long time testing before goes upstream.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Bryan Mason <bmason@redhat.com>
References: https://lkml.org/lkml/2009/11/11/223
References: https://bugzilla.redhat.com/show_bug.cgi?id=504703
References: https://bugzilla.novell.com/show_bug.cgi?id=797042
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
spaces are used for indent in 3 places of tty/pty.c, we change it to tab.
Signed-off-by: Cong Ding <dinggnu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
the "\n" in panic message is excess, so we remove it in tty/pty.c as what it
is used in other places.
Signed-off-by: Cong Ding <dinggnu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
Now, the one where most of tty_port_tty_get gets removed:
tty_flip_buffer_push.
IOW we also closed all the races in drivers not using tty_port_tty_get
at all yet.
Also we move tty_flip_buffer_push declaration from include/linux/tty.h
to include/linux/tty_flip.h to all others while we are changing it
anyway.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Now, we start converting tty buffer functions to actually use
tty_port. This will allow us to get rid of the need of tty in many
call sites. Only tty_port will needed and hence no more
tty_port_tty_get in those paths.
tty_insert_flip_string this time.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linus Torvalds