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  1. 18 Dec, 2015 1 commit
  3. 14 Dec, 2015 35 commits
  5. 13 Dec, 2015 4 commits
    • David Howells's avatar
      FS-Cache: Handle a write to the page immediately beyond the EOF marker · c8aedb3b
      David Howells authored 
      commit 102f4d90 upstream.

Handle a write being requested to the page immediately beyond the EOF
marker on a cache object.  Currently this gets an assertion failure in
CacheFiles because the EOF marker is used there to encode information about
a partial page at the EOF - which could lead to an unknown blank spot in
the file if we extend the file over it.

The problem is actually in fscache where we check the index of the page
being written against store_limit.  store_limit is set to the number of
pages that we're allowed to store by fscache_set_store_limit() - which
means it's one more than the index of the last page we're allowed to store.
The problem is that we permit writing to a page with an index _equal_ to
the store limit - when we should reject that case.

Whilst we're at it, change the triggered assertion in CacheFiles to just
return -ENOBUFS instead.

The assertion failure looks something like this:

CacheFiles: Assertion failed
1000 < 7b1 is false
------------[ cut here ]------------
kernel BUG at fs/cachefiles/rdwr.c:962!
...
RIP: 0010:[<ffffffffa02c9e83>]  [<ffffffffa02c9e83>] cachefiles_write_page+0x273/0x2d0 [cachefiles]
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
[ kamal: backport to 3.13-stable: no __kernel_write(); thanks Ben H. ]
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
      c8aedb3b
    • Mathias Krause's avatar
      printk: prevent userland from spoofing kernel messages · fd7060f6
      Mathias Krause authored 
      commit 3824657c upstream.

The following statement of ABI/testing/dev-kmsg is not quite right:

   It is not possible to inject messages from userspace with the
   facility number LOG_KERN (0), to make sure that the origin of the
   messages can always be reliably determined.

Userland actually can inject messages with a facility of 0 by abusing the
fact that the facility is stored in a u8 data type.  By using a facility
which is a multiple of 256 the assignment of msg->facility in log_store()
implicitly truncates it to 0, i.e.  LOG_KERN, allowing users of /dev/kmsg
to spoof kernel messages as shown below:

The following call...
   # printf '<%d>Kernel panic - not syncing: beer empty\n' 0 >/dev/kmsg
...leads to the following log entry (dmesg -x | tail -n 1):
   user  :emerg : [   66.137758] Kernel panic - not syncing: beer empty

However, this call...
   # printf '<%d>Kernel panic - not syncing: beer empty\n' 0x800 >/dev/kmsg
...leads to the slightly different log entry (note the kernel facility):
   kern  :emerg : [   74.177343] Kernel panic - not syncing: beer empty

Fix that by limiting the user provided facility to 8 bit right from the
beginning and catch the truncation early.

Fixes: 7ff9554b ("printk: convert byte-buffer to variable-length...")
Signed-off-by: default avatarMathias Krause <minipli@googlemail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Alex Elder <elder@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: Kay Sievers <kay@vrfy.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
[ kamal: backport to 3.13-stable: retain local 'int i' ]
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
      fd7060f6
    • Takashi Iwai's avatar
      ALSA: hda - Disable 64bit address for Creative HDA controllers · cd21931f
      Takashi Iwai authored 
      commit cadd16ea upstream.

We've had many reports that some Creative sound cards with CA0132
don't work well.  Some reported that it starts working after reloading
the module, while some reported it starts working when a 32bit kernel
is used.  All these facts seem implying that the chip fails to
communicate when the buffer is located in 64bit address.

This patch addresses these issues by just adding AZX_DCAPS_NO_64BIT
flag to the corresponding PCI entries.  I casually had a chance to
test an SB Recon3D board, and indeed this seems helping.

Although this hasn't been tested on all Creative devices, it's safer
to assume that this restriction applies to the rest of them, too.  So
the flag is applied to all Creative entries.
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
[ kamal: backport to 3.13-stable: context ]
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
      cd21931f
    • Ingo Molnar's avatar
      fs/proc, core/debug: Don't expose absolute kernel addresses via wchan · a9ba345c
      Ingo Molnar authored 
      commit b2f73922 upstream.

So the /proc/PID/stat 'wchan' field (the 30th field, which contains
the absolute kernel address of the kernel function a task is blocked in)
leaks absolute kernel addresses to unprivileged user-space:

        seq_put_decimal_ull(m, ' ', wchan);

The absolute address might also leak via /proc/PID/wchan as well, if
KALLSYMS is turned off or if the symbol lookup fails for some reason:

static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
                          struct pid *pid, struct task_struct *task)
{
        unsigned long wchan;
        char symname[KSYM_NAME_LEN];

        wchan = get_wchan(task);

        if (lookup_symbol_name(wchan, symname) < 0) {
                if (!ptrace_may_access(task, PTRACE_MODE_READ))
                        return 0;
                seq_printf(m, "%lu", wchan);
        } else {
                seq_printf(m, "%s", symname);
        }

        return 0;
}

This isn't ideal, because for example it trivially leaks the KASLR offset
to any local attacker:

  fomalhaut:~> printf "%016lx\n" $(cat /proc/$$/stat | cut -d' ' -f35)
  ffffffff8123b380

Most real-life uses of wchan are symbolic:

  ps -eo pid:10,tid:10,wchan:30,comm

and procps uses /proc/PID/wchan, not the absolute address in /proc/PID/stat:

  triton:~/tip> strace -f ps -eo pid:10,tid:10,wchan:30,comm 2>&1 | grep wchan | tail -1
  open("/proc/30833/wchan", O_RDONLY)     = 6

There's one compatibility quirk here: procps relies on whether the
absolute value is non-zero - and we can provide that functionality
by outputing "0" or "1" depending on whether the task is blocked
(whether there's a wchan address).

These days there appears to be very little legitimate reason
user-space would be interested in  the absolute address. The
absolute address is mostly historic: from the days when we
didn't have kallsyms and user-space procps had to do the
decoding itself via the System.map.

So this patch sets all numeric output to "0" or "1" and keeps only
symbolic output, in /proc/PID/wchan.

( The absolute sleep address can generally still be profiled via
  perf, by tasks with sufficient privileges. )
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150930135917.GA3285@gmail.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
[ kamal: backport to 3.16-stable: proc_pid_wchan context ]
Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
      a9ba345c
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