linux-stable/lib/strnlen_user.c
Linus Torvalds 23b7776290 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:
 "The main changes are:

   - lockless wakeup support for futexes and IPC message queues
     (Davidlohr Bueso, Peter Zijlstra)

   - Replace spinlocks with atomics in thread_group_cputimer(), to
     improve scalability (Jason Low)

   - NUMA balancing improvements (Rik van Riel)

   - SCHED_DEADLINE improvements (Wanpeng Li)

   - clean up and reorganize preemption helpers (Frederic Weisbecker)

   - decouple page fault disabling machinery from the preemption
     counter, to improve debuggability and robustness (David
     Hildenbrand)

   - SCHED_DEADLINE documentation updates (Luca Abeni)

   - topology CPU masks cleanups (Bartosz Golaszewski)

   - /proc/sched_debug improvements (Srikar Dronamraju)"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (79 commits)
  sched/deadline: Remove needless parameter in dl_runtime_exceeded()
  sched: Remove superfluous resetting of the p->dl_throttled flag
  sched/deadline: Drop duplicate init_sched_dl_class() declaration
  sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target
  sched/deadline: Make init_sched_dl_class() __init
  sched/deadline: Optimize pull_dl_task()
  sched/preempt: Add static_key() to preempt_notifiers
  sched/preempt: Fix preempt notifiers documentation about hlist_del() within unsafe iteration
  sched/stop_machine: Fix deadlock between multiple stop_two_cpus()
  sched/debug: Add sum_sleep_runtime to /proc/<pid>/sched
  sched/debug: Replace vruntime with wait_sum in /proc/sched_debug
  sched/debug: Properly format runnable tasks in /proc/sched_debug
  sched/numa: Only consider less busy nodes as numa balancing destinations
  Revert 095bebf61a ("sched/numa: Do not move past the balance point if unbalanced")
  sched/fair: Prevent throttling in early pick_next_task_fair()
  preempt: Reorganize the notrace definitions a bit
  preempt: Use preempt_schedule_context() as the official tracing preemption point
  sched: Make preempt_schedule_context() function-tracing safe
  x86: Remove cpu_sibling_mask() and cpu_core_mask()
  x86: Replace cpu_**_mask() with topology_**_cpumask()
  ...
2015-06-22 15:52:04 -07:00

148 lines
4.1 KiB
C

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/uaccess.h>
#include <asm/word-at-a-time.h>
/* Set bits in the first 'n' bytes when loaded from memory */
#ifdef __LITTLE_ENDIAN
# define aligned_byte_mask(n) ((1ul << 8*(n))-1)
#else
# define aligned_byte_mask(n) (~0xfful << (BITS_PER_LONG - 8 - 8*(n)))
#endif
/*
* Do a strnlen, return length of string *with* final '\0'.
* 'count' is the user-supplied count, while 'max' is the
* address space maximum.
*
* Return 0 for exceptions (which includes hitting the address
* space maximum), or 'count+1' if hitting the user-supplied
* maximum count.
*
* NOTE! We can sometimes overshoot the user-supplied maximum
* if it fits in a aligned 'long'. The caller needs to check
* the return value against "> max".
*/
static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
{
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
long align, res = 0;
unsigned long c;
/*
* Truncate 'max' to the user-specified limit, so that
* we only have one limit we need to check in the loop
*/
if (max > count)
max = count;
/*
* Do everything aligned. But that means that we
* need to also expand the maximum..
*/
align = (sizeof(long) - 1) & (unsigned long)src;
src -= align;
max += align;
if (unlikely(__get_user(c,(unsigned long __user *)src)))
return 0;
c |= aligned_byte_mask(align);
for (;;) {
unsigned long data;
if (has_zero(c, &data, &constants)) {
data = prep_zero_mask(c, data, &constants);
data = create_zero_mask(data);
return res + find_zero(data) + 1 - align;
}
res += sizeof(unsigned long);
/* We already handled 'unsigned long' bytes. Did we do it all ? */
if (unlikely(max <= sizeof(unsigned long)))
break;
max -= sizeof(unsigned long);
if (unlikely(__get_user(c,(unsigned long __user *)(src+res))))
return 0;
}
res -= align;
/*
* Uhhuh. We hit 'max'. But was that the user-specified maximum
* too? If so, return the marker for "too long".
*/
if (res >= count)
return count+1;
/*
* Nope: we hit the address space limit, and we still had more
* characters the caller would have wanted. That's 0.
*/
return 0;
}
/**
* strnlen_user: - Get the size of a user string INCLUDING final NUL.
* @str: The string to measure.
* @count: Maximum count (including NUL character)
*
* Context: User context only. This function may sleep if pagefaults are
* enabled.
*
* Get the size of a NUL-terminated string in user space.
*
* Returns the size of the string INCLUDING the terminating NUL.
* If the string is too long, returns a number larger than @count. User
* has to check the return value against "> count".
* On exception (or invalid count), returns 0.
*
* NOTE! You should basically never use this function. There is
* almost never any valid case for using the length of a user space
* string, since the string can be changed at any time by other
* threads. Use "strncpy_from_user()" instead to get a stable copy
* of the string.
*/
long strnlen_user(const char __user *str, long count)
{
unsigned long max_addr, src_addr;
if (unlikely(count <= 0))
return 0;
max_addr = user_addr_max();
src_addr = (unsigned long)str;
if (likely(src_addr < max_addr)) {
unsigned long max = max_addr - src_addr;
return do_strnlen_user(str, count, max);
}
return 0;
}
EXPORT_SYMBOL(strnlen_user);
/**
* strlen_user: - Get the size of a user string INCLUDING final NUL.
* @str: The string to measure.
*
* Context: User context only. This function may sleep if pagefaults are
* enabled.
*
* Get the size of a NUL-terminated string in user space.
*
* Returns the size of the string INCLUDING the terminating NUL.
* On exception, returns 0.
*
* If there is a limit on the length of a valid string, you may wish to
* consider using strnlen_user() instead.
*/
long strlen_user(const char __user *str)
{
unsigned long max_addr, src_addr;
max_addr = user_addr_max();
src_addr = (unsigned long)str;
if (likely(src_addr < max_addr)) {
unsigned long max = max_addr - src_addr;
return do_strnlen_user(str, ~0ul, max);
}
return 0;
}
EXPORT_SYMBOL(strlen_user);