The controversial part of this patch is that I've changed it so we now
prevent integer overflows for VME_USER types and before we didn't. I
view it as kernel-hardening. I looked at a couple places that used
VME_USER types and they seemed pretty suspicious so I'm pretty sure
preventing overflows here is a good idea.
The most common problem which this function is for cases like VME_A16
where we don't put an upper bound on "size" so you could have "size" set
to U64_MAX and a valid vme_base would overflow the "vme_base + size"
into the valid range as well.
In the VME_A64 case, the integer overflow checking doesn't work because
"U64_MAX + 1" has an integer overflow and it's just a complicated way of
saying zero. That VME_A64 case is sort of interesting as well because
there is a VME_A64_MAX define which is set to "U64_MAX + 1". The
compiler will never let anyone use it since it can't be stored in a u64
variable... With my patch it's now limited to just U64_MAX.
Anyway, I put one integer overflow check at the start of the function
and deleted all existing checks.
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
diff --git a/drivers/vme/vme.c b/drivers/vme/vme.c
index 6a3ead42aba8..5b4c898d7509 100644
--- a/drivers/vme/vme.c
+++ b/drivers/vme/vme.c
@@ -208,29 +208,27 @@ int vme_check_window(u32 aspace, unsigned long long vme_base,
{
int retval = 0;
+ if (vme_base + size < size)
+ return -EINVAL;
+
switch (aspace) {
case VME_A16:
- if (((vme_base + size) > VME_A16_MAX) ||
- (vme_base > VME_A16_MAX))
+ if (vme_base + size > VME_A16_MAX)
retval = -EFAULT;
break;
case VME_A24:
- if (((vme_base + size) > VME_A24_MAX) ||
- (vme_base > VME_A24_MAX))
+ if (vme_base + size > VME_A24_MAX)
retval = -EFAULT;
break;
case VME_A32:
- if (((vme_base + size) > VME_A32_MAX) ||
- (vme_base > VME_A32_MAX))
+ if (vme_base + size > VME_A32_MAX)
retval = -EFAULT;
break;
case VME_A64:
- if ((size != 0) && (vme_base > U64_MAX + 1 - size))
- retval = -EFAULT;
+ /* The VME_A64_MAX limit is actually U64_MAX + 1 */
break;
case VME_CRCSR:
- if (((vme_base + size) > VME_CRCSR_MAX) ||
- (vme_base > VME_CRCSR_MAX))
+ if (vme_base + size > VME_CRCSR_MAX)
retval = -EFAULT;
break;
case VME_USER1:
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