mirror of
https://github.com/torvalds/linux.git
synced 2024-11-30 08:01:59 +00:00
ab10ae1c3b
The range passed to user_access_begin() by strncpy_from_user() and
strnlen_user() starts at 'src' and goes up to the limit of userspace
although reads will be limited by the 'count' param.
On 32 bits powerpc (book3s/32) access has to be granted for each
256Mbytes segment and the cost increases with the number of segments to
unlock.
Limit the range with 'count' param.
Fixes: 594cc251fd ("make 'user_access_begin()' do 'access_ok()'")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
128 lines
3.2 KiB
C
128 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/compiler.h>
|
|
#include <linux/export.h>
|
|
#include <linux/kasan-checks.h>
|
|
#include <linux/thread_info.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/mm.h>
|
|
|
|
#include <asm/byteorder.h>
|
|
#include <asm/word-at-a-time.h>
|
|
|
|
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
|
|
#define IS_UNALIGNED(src, dst) 0
|
|
#else
|
|
#define IS_UNALIGNED(src, dst) \
|
|
(((long) dst | (long) src) & (sizeof(long) - 1))
|
|
#endif
|
|
|
|
/*
|
|
* Do a strncpy, return length of string without final '\0'.
|
|
* 'count' is the user-supplied count (return 'count' if we
|
|
* hit it), 'max' is the address space maximum (and we return
|
|
* -EFAULT if we hit it).
|
|
*/
|
|
static inline long do_strncpy_from_user(char *dst, const char __user *src,
|
|
unsigned long count, unsigned long max)
|
|
{
|
|
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
|
|
unsigned long res = 0;
|
|
|
|
if (IS_UNALIGNED(src, dst))
|
|
goto byte_at_a_time;
|
|
|
|
while (max >= sizeof(unsigned long)) {
|
|
unsigned long c, data;
|
|
|
|
/* Fall back to byte-at-a-time if we get a page fault */
|
|
unsafe_get_user(c, (unsigned long __user *)(src+res), byte_at_a_time);
|
|
|
|
*(unsigned long *)(dst+res) = c;
|
|
if (has_zero(c, &data, &constants)) {
|
|
data = prep_zero_mask(c, data, &constants);
|
|
data = create_zero_mask(data);
|
|
return res + find_zero(data);
|
|
}
|
|
res += sizeof(unsigned long);
|
|
max -= sizeof(unsigned long);
|
|
}
|
|
|
|
byte_at_a_time:
|
|
while (max) {
|
|
char c;
|
|
|
|
unsafe_get_user(c,src+res, efault);
|
|
dst[res] = c;
|
|
if (!c)
|
|
return res;
|
|
res++;
|
|
max--;
|
|
}
|
|
|
|
/*
|
|
* Uhhuh. We hit 'max'. But was that the user-specified maximum
|
|
* too? If so, that's ok - we got as much as the user asked for.
|
|
*/
|
|
if (res >= count)
|
|
return res;
|
|
|
|
/*
|
|
* Nope: we hit the address space limit, and we still had more
|
|
* characters the caller would have wanted. That's an EFAULT.
|
|
*/
|
|
efault:
|
|
return -EFAULT;
|
|
}
|
|
|
|
/**
|
|
* strncpy_from_user: - Copy a NUL terminated string from userspace.
|
|
* @dst: Destination address, in kernel space. This buffer must be at
|
|
* least @count bytes long.
|
|
* @src: Source address, in user space.
|
|
* @count: Maximum number of bytes to copy, including the trailing NUL.
|
|
*
|
|
* Copies a NUL-terminated string from userspace to kernel space.
|
|
*
|
|
* On success, returns the length of the string (not including the trailing
|
|
* NUL).
|
|
*
|
|
* If access to userspace fails, returns -EFAULT (some data may have been
|
|
* copied).
|
|
*
|
|
* If @count is smaller than the length of the string, copies @count bytes
|
|
* and returns @count.
|
|
*/
|
|
long strncpy_from_user(char *dst, const char __user *src, long count)
|
|
{
|
|
unsigned long max_addr, src_addr;
|
|
|
|
if (unlikely(count <= 0))
|
|
return 0;
|
|
|
|
max_addr = user_addr_max();
|
|
src_addr = (unsigned long)untagged_addr(src);
|
|
if (likely(src_addr < max_addr)) {
|
|
unsigned long max = max_addr - src_addr;
|
|
long retval;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
kasan_check_write(dst, count);
|
|
check_object_size(dst, count, false);
|
|
if (user_access_begin(src, max)) {
|
|
retval = do_strncpy_from_user(dst, src, count, max);
|
|
user_access_end();
|
|
return retval;
|
|
}
|
|
}
|
|
return -EFAULT;
|
|
}
|
|
EXPORT_SYMBOL(strncpy_from_user);
|