linux-toradex.git/ipc, branch v3.10.78

ipc: fix compat msgrcv with negative msgtyp

2015-04-19T08:10:50+00:00

commit e7ca2552369c1dfe0216c626baf82c3d83ec36bb upstream.

Compat function takes msgtyp argument as u32 and passes it down to
do_msgrcv which results in casting to long, thus the sign is lost and we
get a big positive number instead.

Cast the argument to signed type before passing it down.

Signed-off-by: Mateusz Guzik 
Reported-by: Gabriellla Schmidt 
Cc: Al Viro 
Cc: Davidlohr Bueso 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Cc: Masanari Iida 
Signed-off-by: Greg Kroah-Hartman

ipc: always handle a new value of auto_msgmni

2014-11-21T17:22:54+00:00

commit 1195d94e006b23c6292e78857e154872e33b6d7e upstream.

proc_dointvec_minmax() returns zero if a new value has been set.  So we
don't need to check all charecters have been handled.

Below you can find two examples.  In the new value has not been handled
properly.

$ strace ./a.out
open("/proc/sys/kernel/auto_msgmni", O_WRONLY) = 3
write(3, "0\n\0", 3)                    = 2
close(3)                                = 0
exit_group(0)
$ cat /sys/kernel/debug/tracing/trace

$strace ./a.out
open("/proc/sys/kernel/auto_msgmni", O_WRONLY) = 3
write(3, "0\n", 2)                      = 2
close(3)                                = 0

$ cat /sys/kernel/debug/tracing/trace
a.out-697   [000] ....  3280.998235: unregister_ipcns_notifier <-proc_ipcauto_dointvec_minmax

Fixes: 9eefe520c814 ("ipc: do not use a negative value to re-enable msgmni automatic recomputin")
Signed-off-by: Andrey Vagin 
Cc: Mathias Krause 
Cc: Manfred Spraul 
Cc: Joe Perches 
Cc: Davidlohr Bueso 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc: Fix 2 bugs in msgrcv() MSG_COPY implementation

2014-03-24T04:38:17+00:00

commit 4f87dac386cc43d5525da7a939d4b4e7edbea22c upstream.

While testing and documenting the msgrcv() MSG_COPY flag that Stanislav
Kinsbursky added in commit 4a674f34ba04 ("ipc: introduce message queue
copy feature" => kernel 3.8), I discovered a couple of bugs in the
implementation.  The two bugs concern MSG_COPY interactions with other
msgrcv() flags, namely:

 (A) MSG_COPY + MSG_EXCEPT
 (B) MSG_COPY + !IPC_NOWAIT

The bugs are distinct (and the fix for the first one is obvious),
however my fix for both is a single-line patch, which is why I'm
combining them in a single mail, rather than writing two mails+patches.

 ===== (A) MSG_COPY + MSG_EXCEPT =====

With the addition of the MSG_COPY flag, there are now two msgrcv()
flags--MSG_COPY and MSG_EXCEPT--that modify the meaning of the 'msgtyp'
argument in unrelated ways.  Specifying both in the same call is a
logical error that is currently permitted, with the effect that MSG_COPY
has priority and MSG_EXCEPT is ignored.  The call should give an error
if both flags are specified.  The patch below implements that behavior.

 ===== (B) (B) MSG_COPY + !IPC_NOWAIT =====

The test code that was submitted in commit 3a665531a3b7 ("selftests: IPC
message queue copy feature test") shows MSG_COPY being used in
conjunction with IPC_NOWAIT.  In other words, if there is no message at
the position 'msgtyp'.  return immediately with the error in ENOMSG.

What was not (fully) tested is the behavior if MSG_COPY is specified
*without* IPC_NOWAIT, and there is an odd behavior.  If the queue
contains less than 'msgtyp' messages, then the call blocks until the
next message is written to the queue.  At that point, the msgrcv() call
returns a copy of the newly added message, regardless of whether that
message is at the ordinal position 'msgtyp'.  This is clearly bogus, and
problematic for applications that might want to make use of the MSG_COPY
flag.

I considered the following possible solutions to this problem:

 (1) Force the call to block until a message *does* appear at the
     position 'msgtyp'.

 (2) If the MSG_COPY flag is specified, the kernel should implicitly add
     IPC_NOWAIT, so that the call fails with ENOMSG for this case.

 (3) If the MSG_COPY flag is specified, but IPC_NOWAIT is not, generate
     an error (probably, EINVAL is the right one).

I do not know if any application would really want to have the
functionality of solution (1), especially since an application can
determine in advance the number of messages in the queue using msgctl()
IPC_STAT.  Obviously, this solution would be the most work to implement.

Solution (2) would have the effect of silently fixing any applications
that tried to employ broken behavior.  However, it would mean that if we
later decided to implement solution (1), then user-space could not
easily detect what the kernel supports (but, since I'm somewhat doubtful
that solution (1) is needed, I'm not sure that this is much of a
problem).

Solution (3) would have the effect of informing broken applications that
they are doing something broken.  The downside is that this would cause
a ABI breakage for any applications that are currently employing the
broken behavior.  However:

a) Those applications are almost certainly not getting the results they
   expect.
b) Possibly, those applications don't even exist, because MSG_COPY is
   currently hidden behind CONFIG_CHECKPOINT_RESTORE.

The upside of solution (3) is that if we later decided to implement
solution (1), user-space could determine what the kernel supports, via
the error return.

In my view, solution (3) is mildly preferable to solution (2), and
solution (1) could still be done later if anyone really cares.  The
patch below implements solution (3).

PS.  For anyone out there still listening, it's the usual story:
documenting an API (and the thinking about, and the testing of the API,
that documentation entails) is the one of the single best ways of
finding bugs in the API, as I've learned from a lot of experience.  Best
to do that documentation before releasing the API.

Signed-off-by: Michael Kerrisk 
Acked-by: Stanislav Kinsbursky 
Cc: Stanislav Kinsbursky 
Cc: Serge Hallyn 
Cc: "Eric W. Biederman" 
Cc: Pavel Emelyanov 
Cc: Al Viro 
Cc: KOSAKI Motohiro 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc,mqueue: remove limits for the amount of system-wide queues

2014-03-07T05:30:12+00:00

commit f3713fd9cff733d9df83116422d8e4af6e86b2bb upstream.

Commit 93e6f119c0ce ("ipc/mqueue: cleanup definition names and
locations") added global hardcoded limits to the amount of message
queues that can be created.  While these limits are per-namespace,
reality is that it ends up breaking userspace applications.
Historically users have, at least in theory, been able to create up to
INT_MAX queues, and limiting it to just 1024 is way too low and dramatic
for some workloads and use cases.  For instance, Madars reports:

 "This update imposes bad limits on our multi-process application.  As
  our app uses approaches that each process opens its own set of queues
  (usually something about 3-5 queues per process).  In some scenarios
  we might run up to 3000 processes or more (which of-course for linux
  is not a problem).  Thus we might need up to 9000 queues or more.  All
  processes run under one user."

Other affected users can be found in launchpad bug #1155695:
  https://bugs.launchpad.net/ubuntu/+source/manpages/+bug/1155695

Instead of increasing this limit, revert it entirely and fallback to the
original way of dealing queue limits -- where once a user's resource
limit is reached, and all memory is used, new queues cannot be created.

Signed-off-by: Davidlohr Bueso 
Reported-by: Madars Vitolins 
Acked-by: Doug Ledford 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

audit: fix mq_open and mq_unlink to add the MQ root as a hidden parent audit_names record

2013-12-04T18:57:03+00:00

commit 79f6530cb59e2a0af6953742a33cc29e98ca631c upstream.

The old audit PATH records for mq_open looked like this:

  type=PATH msg=audit(1366282323.982:869): item=1 name=(null) inode=6777
  dev=00:0c mode=041777 ouid=0 ogid=0 rdev=00:00
  obj=system_u:object_r:tmpfs_t:s15:c0.c1023
  type=PATH msg=audit(1366282323.982:869): item=0 name="test_mq" inode=26732
  dev=00:0c mode=0100700 ouid=0 ogid=0 rdev=00:00
  obj=staff_u:object_r:user_tmpfs_t:s15:c0.c1023

...with the audit related changes that went into 3.7, they now look like this:

  type=PATH msg=audit(1366282236.776:3606): item=2 name=(null) inode=66655
  dev=00:0c mode=0100700 ouid=0 ogid=0 rdev=00:00
  obj=staff_u:object_r:user_tmpfs_t:s15:c0.c1023
  type=PATH msg=audit(1366282236.776:3606): item=1 name=(null) inode=6926
  dev=00:0c mode=041777 ouid=0 ogid=0 rdev=00:00
  obj=system_u:object_r:tmpfs_t:s15:c0.c1023
  type=PATH msg=audit(1366282236.776:3606): item=0 name="test_mq"

Both of these look wrong to me.  As Steve Grubb pointed out:

 "What we need is 1 PATH record that identifies the MQ.  The other PATH
  records probably should not be there."

Fix it to record the mq root as a parent, and flag it such that it
should be hidden from view when the names are logged, since the root of
the mq filesystem isn't terribly interesting.  With this change, we get
a single PATH record that looks more like this:

  type=PATH msg=audit(1368021604.836:484): item=0 name="test_mq" inode=16914
  dev=00:0c mode=0100644 ouid=0 ogid=0 rdev=00:00
  obj=unconfined_u:object_r:user_tmpfs_t:s0

In order to do this, a new audit_inode_parent_hidden() function is
added.  If we do it this way, then we avoid having the existing callers
of audit_inode needing to do any sort of flag conversion if auditing is
inactive.

Signed-off-by: Jeff Layton 
Reported-by: Jiri Jaburek 
Cc: Steve Grubb 
Cc: Eric Paris 
Cc: Al Viro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc/sem.c: synchronize semop and semctl with IPC_RMID

2013-12-04T18:56:12+00:00

commit 6e224f94597842c5eb17f1fc2208d20b6f7f7d49 upstream.

After acquiring the semlock spinlock, operations must test that the
array is still valid.

 - semctl() and exit_sem() would walk stale linked lists (ugly, but
   should be ok: all lists are empty)

 - semtimedop() would sleep forever - and if woken up due to a signal -
   access memory after free.

The patch also:
 - standardizes the tests for .deleted, so that all tests in one
   function leave the function with the same approach.
 - unconditionally tests for .deleted immediately after every call to
   sem_lock - even it it means that for semctl(GETALL), .deleted will be
   tested twice.

Both changes make the review simpler: After every sem_lock, there must
be a test of .deleted, followed by a goto to the cleanup code (if the
function uses "goto cleanup").

The only exception is semctl_down(): If sem_ids().rwsem is locked, then
the presence in ids->ipcs_idr is equivalent to !.deleted, thus no
additional test is required.

Signed-off-by: Manfred Spraul 
Cc: Mike Galbraith 
Acked-by: Davidlohr Bueso 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc: update locking scheme comments

2013-12-04T18:56:12+00:00

commit 18ccee263c7e250a57f01c9434658f11f4118a64 upstream.

The initial documentation was a bit incomplete, update accordingly.

[akpm@linux-foundation.org: make it more readable in 80 columns]
Signed-off-by: Davidlohr Bueso 
Acked-by: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc, msg: forbid negative values for "msg{max,mnb,mni}"

2013-12-04T18:56:11+00:00

commit 9bf76ca325d5e9208eb343f7bd4cc666f703ed30 upstream.

Negative message lengths make no sense -- so don't do negative queue
lenghts or identifier counts. Prevent them from getting negative.

Also change the underlying data types to be unsigned to avoid hairy
surprises with sign extensions in cases where those variables get
evaluated in unsigned expressions with bigger data types, e.g size_t.

In case a user still wants to have "unlimited" sizes she could just use
INT_MAX instead.

Signed-off-by: Mathias Krause 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc, msg: fix message length check for negative values

2013-12-04T18:56:10+00:00

commit 4e9b45a19241354daec281d7a785739829b52359 upstream.

On 64 bit systems the test for negative message sizes is bogus as the
size, which may be positive when evaluated as a long, will get truncated
to an int when passed to load_msg().  So a long might very well contain a
positive value but when truncated to an int it would become negative.

That in combination with a small negative value of msg_ctlmax (which will
be promoted to an unsigned type for the comparison against msgsz, making
it a big positive value and therefore make it pass the check) will lead to
two problems: 1/ The kmalloc() call in alloc_msg() will allocate a too
small buffer as the addition of alen is effectively a subtraction.  2/ The
copy_from_user() call in load_msg() will first overflow the buffer with
userland data and then, when the userland access generates an access
violation, the fixup handler copy_user_handle_tail() will try to fill the
remainder with zeros -- roughly 4GB.  That almost instantly results in a
system crash or reset.

  ,-[ Reproducer (needs to be run as root) ]--
  | #include 
  | #include 
  | #include 
  | #include 
  |
  | int main(void) {
  |     long msg = 1;
  |     int fd;
  |
  |     fd = open("/proc/sys/kernel/msgmax", O_WRONLY);
  |     write(fd, "-1", 2);
  |     close(fd);
  |
  |     msgsnd(0, &msg, 0xfffffff0, IPC_NOWAIT);
  |
  |     return 0;
  | }
  '---

Fix the issue by preventing msgsz from getting truncated by consistently
using size_t for the message length.  This way the size checks in
do_msgsnd() could still be passed with a negative value for msg_ctlmax but
we would fail on the buffer allocation in that case and error out.

Also change the type of m_ts from int to size_t to avoid similar nastiness
in other code paths -- it is used in similar constructs, i.e.  signed vs.
unsigned checks.  It should never become negative under normal
circumstances, though.

Setting msg_ctlmax to a negative value is an odd configuration and should
be prevented.  As that might break existing userland, it will be handled
in a separate commit so it could easily be reverted and reworked without
reintroducing the above described bug.

Hardening mechanisms for user copy operations would have catched that bug
early -- e.g.  checking slab object sizes on user copy operations as the
usercopy feature of the PaX patch does.  Or, for that matter, detect the
long vs.  int sign change due to truncation, as the size overflow plugin
of the very same patch does.

[akpm@linux-foundation.org: fix i386 min() warnings]
Signed-off-by: Mathias Krause 
Cc: Pax Team 
Cc: Davidlohr Bueso 
Cc: Brad Spengler 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

ipc,shm: fix shm_file deletion races

2013-11-29T19:11:41+00:00

commit a399b29dfbaaaf91162b2dc5a5875dd51bbfa2a1 upstream.

When IPC_RMID races with other shm operations there's potential for
use-after-free of the shm object's associated file (shm_file).

Here's the race before this patch:

  TASK 1                     TASK 2
  ------                     ------
  shm_rmid()
    ipc_lock_object()
                             shmctl()
                             shp = shm_obtain_object_check()

    shm_destroy()
      shum_unlock()
      fput(shp->shm_file)
                             ipc_lock_object()
                             shmem_lock(shp->shm_file)
                             

The oops is caused because shm_destroy() calls fput() after dropping the
ipc_lock.  fput() clears the file's f_inode, f_path.dentry, and
f_path.mnt, which causes various NULL pointer references in task 2.  I
reliably see the oops in task 2 if with shmlock, shmu

This patch fixes the races by:
1) set shm_file=NULL in shm_destroy() while holding ipc_object_lock().
2) modify at risk operations to check shm_file while holding
   ipc_object_lock().

Example workloads, which each trigger oops...

Workload 1:
  while true; do
    id=$(shmget 1 4096)
    shm_rmid $id &
    shmlock $id &
    wait
  done

  The oops stack shows accessing NULL f_inode due to racing fput:
    _raw_spin_lock
    shmem_lock
    SyS_shmctl

Workload 2:
  while true; do
    id=$(shmget 1 4096)
    shmat $id 4096 &
    shm_rmid $id &
    wait
  done

  The oops stack is similar to workload 1 due to NULL f_inode:
    touch_atime
    shmem_mmap
    shm_mmap
    mmap_region
    do_mmap_pgoff
    do_shmat
    SyS_shmat

Workload 3:
  while true; do
    id=$(shmget 1 4096)
    shmlock $id
    shm_rmid $id &
    shmunlock $id &
    wait
  done

  The oops stack shows second fput tripping on an NULL f_inode.  The
  first fput() completed via from shm_destroy(), but a racing thread did
  a get_file() and queued this fput():
    locks_remove_flock
    __fput
    ____fput
    task_work_run
    do_notify_resume
    int_signal

Fixes: c2c737a0461e ("ipc,shm: shorten critical region for shmat")
Fixes: 2caacaa82a51 ("ipc,shm: shorten critical region for shmctl")
Signed-off-by: Greg Thelen 
Cc: Davidlohr Bueso 
Cc: Rik van Riel 
Cc: Manfred Spraul 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman