commit
594cc251fdd0d231d342d88b2fdff4bc42fb0690 upstream.
Originally, the rule used to be that you'd have to do access_ok()
separately, and then user_access_begin() before actually doing the
direct (optimized) user access.
But experience has shown that people then decide not to do access_ok()
at all, and instead rely on it being implied by other operations or
similar. Which makes it very hard to verify that the access has
actually been range-checked.
If you use the unsafe direct user accesses, hardware features (either
SMAP - Supervisor Mode Access Protection - on x86, or PAN - Privileged
Access Never - on ARM) do force you to use user_access_begin(). But
nothing really forces the range check.
By putting the range check into user_access_begin(), we actually force
people to do the right thing (tm), and the range check vill be visible
near the actual accesses. We have way too long a history of people
trying to avoid them.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* checking before using them, but you have to surround them with the
* user_access_begin/end() pair.
*/
-#define user_access_begin() __uaccess_begin()
+static __must_check inline bool user_access_begin(int type,
+ const void __user *ptr,
+ size_t len)
+{
+ if (unlikely(!access_ok(type, ptr, len)))
+ return 0;
+ __uaccess_begin();
+ return 1;
+}
+
+#define user_access_begin(a, b, c) user_access_begin(a, b, c)
#define user_access_end() __uaccess_end()
#define unsafe_put_user(x, ptr, err_label) \
* happened we would make the mistake of assuming that the
* relocations were valid.
*/
- user_access_begin();
+ if (!user_access_begin(VERIFY_WRITE, urelocs, size))
+ goto end_user;
+
for (copied = 0; copied < nreloc; copied++)
unsafe_put_user(-1,
&urelocs[copied].presumed_offset,
struct drm_i915_gem_execbuffer2 *args = data;
struct drm_i915_gem_exec_object2 *exec2_list;
struct drm_syncobj **fences = NULL;
+ const size_t count = args->buffer_count;
int err;
if (args->buffer_count < 1 || args->buffer_count > SIZE_MAX / sz - 1) {
unsigned int i;
/* Copy the new buffer offsets back to the user's exec list. */
- user_access_begin();
+ /*
+ * Note: count * sizeof(*user_exec_list) does not overflow,
+ * because we checked 'count' in check_buffer_count().
+ *
+ * And this range already got effectively checked earlier
+ * when we did the "copy_from_user()" above.
+ */
+ if (!user_access_begin(VERIFY_WRITE, user_exec_list,
+ count * sizeof(*user_exec_list)))
+ goto end_user;
+
for (i = 0; i < args->buffer_count; i++) {
if (!(exec2_list[i].offset & UPDATE))
continue;
probe_kernel_read(&retval, addr, sizeof(retval))
#ifndef user_access_begin
-#define user_access_begin() do { } while (0)
+#define user_access_begin(type, ptr, len) access_ok(type, ptr, len)
#define user_access_end() do { } while (0)
#define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
#define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
- if (!access_ok(VERIFY_READ, umask, bitmap_size / 8))
+ if (!user_access_begin(VERIFY_READ, umask, bitmap_size / 8))
return -EFAULT;
- user_access_begin();
while (nr_compat_longs > 1) {
compat_ulong_t l1, l2;
unsafe_get_user(l1, umask++, Efault);
bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
- if (!access_ok(VERIFY_WRITE, umask, bitmap_size / 8))
+ if (!user_access_begin(VERIFY_WRITE, umask, bitmap_size / 8))
return -EFAULT;
- user_access_begin();
while (nr_compat_longs > 1) {
unsigned long m = *mask++;
unsafe_put_user((compat_ulong_t)m, umask++, Efault);
if (!infop)
return err;
- if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+ if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop)))
return -EFAULT;
- user_access_begin();
unsafe_put_user(signo, &infop->si_signo, Efault);
unsafe_put_user(0, &infop->si_errno, Efault);
unsafe_put_user(info.cause, &infop->si_code, Efault);
if (!infop)
return err;
- if (!access_ok(VERIFY_WRITE, infop, sizeof(*infop)))
+ if (!user_access_begin(VERIFY_WRITE, infop, sizeof(*infop)))
return -EFAULT;
- user_access_begin();
unsafe_put_user(signo, &infop->si_signo, Efault);
unsafe_put_user(0, &infop->si_errno, Efault);
unsafe_put_user(info.cause, &infop->si_code, Efault);
kasan_check_write(dst, count);
check_object_size(dst, count, false);
- user_access_begin();
- retval = do_strncpy_from_user(dst, src, count, max);
- user_access_end();
- return retval;
+ if (user_access_begin(VERIFY_READ, src, max)) {
+ retval = do_strncpy_from_user(dst, src, count, max);
+ user_access_end();
+ return retval;
+ }
}
return -EFAULT;
}
unsigned long max = max_addr - src_addr;
long retval;
- user_access_begin();
- retval = do_strnlen_user(str, count, max);
- user_access_end();
- return retval;
+ if (user_access_begin(VERIFY_READ, str, max)) {
+ retval = do_strnlen_user(str, count, max);
+ user_access_end();
+ return retval;
+ }
}
return 0;
}