summaryrefslogtreecommitdiff
path: root/kernel/compat.c
diff options
context:
space:
mode:
authorHelge Deller <deller@gmx.de>2015-06-04 23:57:18 +0200
committerHelge Deller <deller@gmx.de>2015-06-04 23:57:18 +0200
commit9b7b819ca1e508195feed5ece558dca66adeef05 (patch)
treecf62f858c89c61d5b38052273ff7ca2defb3a818 /kernel/compat.c
parentff25ea8f4eeea252bfcaf65289fa57ba6de080dd (diff)
downloadlinux-sh-9b7b819ca1e508195feed5ece558dca66adeef05.tar.gz
compat: cleanup coding in compat_get_bitmap() and compat_put_bitmap()
In the functions compat_get_bitmap() and compat_put_bitmap() the variable nr_compat_longs stores how many compat_ulong_t words should be copied in a loop. The copy loop itself is this: if (nr_compat_longs-- > 0) { if (__get_user(um, umask)) return -EFAULT; } else { um = 0; } Since nr_compat_longs gets unconditionally decremented in each loop and since it's type is unsigned this could theoretically lead to out of bounds accesses to userspace if nr_compat_longs wraps around to (unsigned)(-1). Although the callers currently do not trigger out-of-bounds accesses, we should better implement the loop in a safe way to completely avoid such warp-arounds. Signed-off-by: Helge Deller <deller@gmx.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'kernel/compat.c')
-rw-r--r--kernel/compat.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/compat.c b/kernel/compat.c
index 24f00610c575..333d364be29d 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -912,7 +912,8 @@ long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask,
* bitmap. We must however ensure the end of the
* kernel bitmap is zeroed.
*/
- if (nr_compat_longs-- > 0) {
+ if (nr_compat_longs) {
+ nr_compat_longs--;
if (__get_user(um, umask))
return -EFAULT;
} else {
@@ -954,7 +955,8 @@ long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask,
* We dont want to write past the end of the userspace
* bitmap.
*/
- if (nr_compat_longs-- > 0) {
+ if (nr_compat_longs) {
+ nr_compat_longs--;
if (__put_user(um, umask))
return -EFAULT;
}