This patch adds an EX_TABLE entry to mvc{p|s|os} usercopy functions that
may be called with KERNEL_DS. In combination with collaborative memory
management, kernel pages marked as unused may trigger an adressing exception
in the usercopy functions. This fixes an unhandled addressing exception bug
where strncpy_from_user() is used with len > strnlen and KERNEL_DS, crossing
a page boundary to an unused page.
Signed-off-by: NGerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Add missing exception table entry so that the kernel can handle
proctection exceptions as well on the cs instruction. Currently only
specification exceptions are handled correctly.
The missing entry allows user space to crash the kernel.

Cc: stable <stable@kernel.org>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

There are several places in the futex code where a spin_lock is held
and still uaccesses happen. Deadlocks are avoided by increasing the
preempt count. The pagefault handler will then not take any locks
but will immediately search the fixup tables.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Introduce pagefault_{disable,enable}() and use these where previously we did
manual preempt increments/decrements to make the pagefault handler do the
atomic thing.

Currently they still rely on the increased preempt count, but do not rely on
the disabled preemption, this might go away in the future.

(NOTE: the extra barrier() in pagefault_disable might fix some holes on
       machines which have too many registers for their own good)

[heiko.carstens@de.ibm.com: s390 fix]
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NNick Piggin <npiggin@suse.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Use a wrapper for copy_to/from_user to chose the best usercopy method.
The mvcos instruction is better for sizes greater than 256 bytes, if
mvcos is not available a page table walk is better for sizes greater
than 1024 bytes. Also removed the redundant copy_to/from_user_std_small
functions.
Signed-off-by: NGerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

A user space program can read uninitialised kernel memory
by appending to a file from a bad address and then reading
the result back. The cause is the copy_from_user function
that does not clear the remaining bytes of the kernel
buffer after it got a fault on the user space address.
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

Introduces a struct uaccess_ops which allows setting user-copy
operations at run-time.
Signed-off-by: NGerald Schaefer <geraldsc@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>