linux-stable.git/drivers/tty, branch v3.16.35

serial: sh-sci: Remove cpufreq notifier to fix crash/deadlock

2016-04-30T22:06:11+00:00

commit ff1cab374ad98f4b9f408525ca9c08992b4ed784 upstream.

The BSP team noticed that there is spin/mutex lock issue on sh-sci when
CPUFREQ is used.  The issue is that the notifier function may call
mutex_lock() while the spinlock is held, which can lead to a BUG().
This may happen if CPUFREQ is changed while another CPU calls
clk_get_rate().

Taking the spinlock was added to the notifier function in commit
e552de2413edad1a ("sh-sci: add platform device private data"), to
protect the list of serial ports against modification during traversal.
At that time the Common Clock Framework didn't exist yet, and
clk_get_rate() just returned clk->rate without taking a mutex.
Note that since commit d535a2305facf9b4 ("serial: sh-sci: Require a
device per port mapping."), there's no longer a list of serial ports to
traverse, and taking the spinlock became superfluous.

To fix the issue, just remove the cpufreq notifier:
  1. The notifier doesn't work correctly: all it does is update the
     stored clock rate; it does not update the divider in the hardware.
     The divider will only be updated when calling sci_set_termios().
     I believe this was broken back in 2004, when the old
     drivers/char/sh-sci.c driver (where the notifier did update the
     divider) was replaced by drivers/serial/sh-sci.c (where the
     notifier just updated port->uartclk).
     Cfr. full-history-linux commits 6f8deaef2e9675d9 ("[PATCH] sh: port
     sh-sci driver to the new API") and 3f73fe878dc9210a ("[PATCH]
     Remove old sh-sci driver").
  2. On modern SoCs, the sh-sci parent clock rate is no longer related
     to the CPU clock rate anyway, so using a cpufreq notifier is
     futile.

Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Ben Hutchings

8250: use callbacks to access UART_DLL/UART_DLM

2016-04-30T22:05:46+00:00

commit 0b41ce991052022c030fd868e03877700220b090 upstream.

Some UART HW has a single register combining UART_DLL/UART_DLM
(this was probably forgotten in the change that introduced the
callbacks, commit b32b19b8ffc05cbd3bf91c65e205f6a912ca15d9)

Fixes: b32b19b8ffc0 ("[SERIAL] 8250: set divisor register correctly ...")

Signed-off-by: Sebastian Frias 
Reviewed-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings

pty: make sure super_block is still valid in final /dev/tty close

2016-02-25T10:34:48+00:00

commit 1f55c718c290616889c04946864a13ef30f64929 upstream.

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 
Reviewed-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Luis Henriques

pty: fix possible use after free of tty->driver_data

2016-02-25T10:34:47+00:00

commit 2831c89f42dcde440cfdccb9fee9f42d54bbc1ef upstream.

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 
Reviewed-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Luis Henriques

serial: omap: Prevent DoS using unprivileged ioctl(TIOCSRS485)

2016-02-25T10:34:47+00:00

commit 308bbc9ab838d0ace0298268c7970ba9513e2c65 upstream.

The omap-serial driver emulates RS485 delays using software timers,
but neglects to clamp the input values from the unprivileged
ioctl(TIOCSRS485). Because the software implementation busy-waits,
malicious userspace could stall the cpu for ~49 days.

Clamp the input values to < 100ms.

Fixes: 4a0ac0f55b18 ("OMAP: add RS485 support")
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques

n_tty: Fix unsafe reference to "other" ldisc

2016-02-17T10:22:43+00:00

commit 6d27a63caad3f13e96cf065d2d96828c2006be6b upstream.

Although n_tty_check_unthrottle() has a valid ldisc reference (since
the tty core gets the ldisc ref in tty_read() before calling the line
discipline read() method), it does not have a valid ldisc reference to
the "other" pty of a pty pair. Since getting an ldisc reference for
tty->link essentially open-codes tty_wakeup(), just replace with the
equivalent tty_wakeup().

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques

tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)

2016-02-16T10:55:25+00:00

commit 5c17c861a357e9458001f021a7afa7aab9937439 upstream.

ioctl(TIOCGETD) retrieves the line discipline id directly from the
ldisc because the line discipline id (c_line) in termios is untrustworthy;
userspace may have set termios via ioctl(TCSETS*) without actually
changing the line discipline via ioctl(TIOCSETD).

However, directly accessing the current ldisc via tty->ldisc is
unsafe; the ldisc ptr dereferenced may be stale if the line discipline
is changing via ioctl(TIOCSETD) or hangup.

Wait for the line discipline reference (just like read() or write())
to retrieve the "current" line discipline id.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
Cc: Moritz Muehlenhoff 
Signed-off-by: Luis Henriques

sysrq: Fix warning in sysrq generated crash.

2016-02-02T19:39:38+00:00

commit 984cf355aeaa8f2eda3861b50d0e8d3e3f77e83b upstream.

Commit 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq") replaced
spin_lock_irqsave() calls with rcu_read_lock() calls in sysrq. Since
rcu_read_lock() does not disable preemption, faulthandler_disabled() in
__do_page_fault() in x86/fault.c returns false. When the code later calls
might_sleep() in the pagefault handler, we get the following warning:

BUG: sleeping function called from invalid context at ../arch/x86/mm/fault.c:1187
in_atomic(): 0, irqs_disabled(): 0, pid: 4706, name: bash
Preemption disabled at:[] printk+0x48/0x4a

To fix this, we release the RCU read lock before we crash.

Tested this patch on linux 3.18 by booting off one of our boards.

Fixes: 984d74a72076a1 ("sysrq: rcu-ify __handle_sysrq")

Signed-off-by: Ani Sinha 
Reviewed-by: Rik van Riel 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Luis Henriques

tty: Fix GPF in flush_to_ldisc()

2016-01-25T10:43:37+00:00

commit 9ce119f318ba1a07c29149301f1544b6c4bea52a upstream.

A line discipline which does not define a receive_buf() method can
can cause a GPF if data is ever received [1]. Oddly, this was known
to the author of n_tracesink in 2011, but never fixed.

[1] GPF report
    BUG: unable to handle kernel NULL pointer dereference at           (null)
    IP: [<          (null)>]           (null)
    PGD 3752d067 PUD 37a7b067 PMD 0
    Oops: 0010 [#1] SMP KASAN
    Modules linked in:
    CPU: 2 PID: 148 Comm: kworker/u10:2 Not tainted 4.4.0-rc2+ #51
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    Workqueue: events_unbound flush_to_ldisc
    task: ffff88006da94440 ti: ffff88006db60000 task.ti: ffff88006db60000
    RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
    RSP: 0018:ffff88006db67b50  EFLAGS: 00010246
    RAX: 0000000000000102 RBX: ffff88003ab32f88 RCX: 0000000000000102
    RDX: 0000000000000000 RSI: ffff88003ab330a6 RDI: ffff88003aabd388
    RBP: ffff88006db67c48 R08: ffff88003ab32f9c R09: ffff88003ab31fb0
    R10: ffff88003ab32fa8 R11: 0000000000000000 R12: dffffc0000000000
    R13: ffff88006db67c20 R14: ffffffff863df820 R15: ffff88003ab31fb8
    FS:  0000000000000000(0000) GS:ffff88006dc00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    CR2: 0000000000000000 CR3: 0000000037938000 CR4: 00000000000006e0
    Stack:
     ffffffff829f46f1 ffff88006da94bf8 ffff88006da94bf8 0000000000000000
     ffff88003ab31fb0 ffff88003aabd438 ffff88003ab31ff8 ffff88006430fd90
     ffff88003ab32f9c ffffed0007557a87 1ffff1000db6cf78 ffff88003ab32078
    Call Trace:
     [] process_one_work+0x8f1/0x17a0 kernel/workqueue.c:2030
     [] worker_thread+0xd4/0x1180 kernel/workqueue.c:2162
     [] kthread+0x1cf/0x270 drivers/block/aoe/aoecmd.c:1302
     [] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
    Code:  Bad RIP value.
    RIP  [<          (null)>]           (null)
     RSP 
    CR2: 0000000000000000
    ---[ end trace a587f8947e54d6ea ]---

Reported-by: Dmitry Vyukov 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Luis Henriques

n_tty: Fix poll() after buffer-limited eof push read

2016-01-25T10:43:37+00:00

commit ac8f3bf8832a405cc6e4dccb1d26d5cb2994d234 upstream.

commit 40d5e0905a03 ("n_tty: Fix EOF push handling") fixed EOF push
for reads. However, that approach still allows a condition mismatch
between poll() and read(), where poll() returns POLLIN but read()
blocks. This state can happen when a previous read() returned because
the user buffer was full and the next character was an EOF not at the
beginning of the line. While the next read() will properly identify
the condition and advance the read buffer tail without improperly
indicating an EOF file condition (ie., read() will not mistakenly
return 0), poll() will mistakenly indicate POLLIN.

Although a possible solution would be to peek at the input buffer
in n_tty_poll(), the better solution in this patch is to eat the
EOF during the previous read() (ie., fix the problem by eliminating
the condition).

The current canon line buffer copy limits the scan for next end-of-line
to the smaller of either,
   a. the remaining user buffer size
   b. completed lines in the input buffer
When the remaining user buffer size is exactly one less than the
end-of-line marked by EOF push, the EOF is not scanned nor skipped
but left for subsequent reads. In the example below, the scan
index 'eol' has stopped at the EOF because it is past the scan
limit of 5 (not because it has found the next set bit in read_flags)

   user buffer [*nr = 5]    _ _ _ _ _

   read_flags               0 0 0 0 0   1
   input buffer             h e l l o [EOF]
                            ^           ^
                           /           /
                         tail        eol

   result: found = 0, tail += 5, *nr += 5

Instead, allow the scan to peek ahead 1 byte (while still limiting the
scan to completed lines in the input buffer). For the example above,

   result: found = 1, tail += 6, *nr += 5

Because the scan limit is now bumped +1 byte, when the scan is
completed, the tail advance and the user buffer copy limit is
re-clamped to *nr when EOF is _not_ found.

Fixes: 40d5e0905a03 ("n_tty: Fix EOF push handling")
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman 
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques