1. To maximize compatibility, sys_sysinfo() tries to replace page
counts by byte counts if no overflow: but its checks forget the
most likely overflow. Just try adding a few 2GB swaps to your
system, watching sysinfo() output as you do so.
2. It nicely defends the caller by doing the overflow test on total
rather than individual fields: but it's wrong to add on totalhigh,
that's included in totalram on all HIGHMEM arches (i386 ppc sparc).
3. Comment says it's dividing values by mem_unit: no, multiplying.
Patch below against 2.4.3-pre3, 2.4.2-ac17, or any 2.4.[0123] tree:
looks more than it really is, used goto rather than further nesting.
--- 2.4.3-pre3/kernel/info.c Tue Sep 5 21:57:57 2000
+++ linux/kernel/info.c Fri Mar 9 18:16:03 2001
@@ -33,41 +33,46 @@
si_swapinfo(&val);
{
- /* If the sum of all the available memory (i.e. ram + swap +
- * highmem) is less then can be stored in a 32 bit unsigned long
- * then we can be binary compatible with 2.2.x kernels. If not,
- * well, who cares since in that case 2.2.x was broken anyways...
+ unsigned long mem_total, sav_total;
+ unsigned int mem_unit, bitcount;
+
+ /* If the sum of all the available memory (i.e. ram + swap)
+ * is less than can be stored in a 32 bit unsigned long then
+ * we can be binary compatible with 2.2.x kernels. If not,
+ * well, in that case 2.2.x was broken anyways...
*
* -Erik Andersen <andersee@debian.org> */
- unsigned long mem_total = val.totalram + val.totalswap;
- if ( !(mem_total < val.totalram || mem_total < val.totalswap)) {
- unsigned long mem_total2 = mem_total + val.totalhigh;
- if (!(mem_total2 < mem_total || mem_total2 < val.totalhigh))
- {
- /* If mem_total did not overflow. Divide all memory values by
- * mem_unit and set mem_unit=1. This leaves things compatible with
- * 2.2.x, and also retains compatibility with earlier 2.4.x
- * kernels... */
-
- int bitcount = 0;
- while (val.mem_unit > 1)
- {
- bitcount++;
- val.mem_unit >>= 1;
- }
- val.totalram <<= bitcount;
- val.freeram <<= bitcount;
- val.sharedram <<= bitcount;
- val.bufferram <<= bitcount;
- val.totalswap <<= bitcount;
- val.freeswap <<= bitcount;
- val.totalhigh <<= bitcount;
- val.freehigh <<= bitcount;
- }
+ mem_total = val.totalram + val.totalswap;
+ if (mem_total < val.totalram || mem_total < val.totalswap)
+ goto out;
+ bitcount = 0;
+ mem_unit = val.mem_unit;
+ while (mem_unit > 1) {
+ bitcount++;
+ mem_unit >>= 1;
+ sav_total = mem_total;
+ mem_total <<= 1;
+ if (mem_total < sav_total)
+ goto out;
}
- }
+ /* If mem_total did not overflow, multiply all memory values by
+ * val.mem_unit and set it to 1. This leaves things compatible
+ * with 2.2.x, and also retains compatibility with earlier 2.4.x
+ * kernels... */
+
+ val.mem_unit = 1;
+ val.totalram <<= bitcount;
+ val.freeram <<= bitcount;
+ val.sharedram <<= bitcount;
+ val.bufferram <<= bitcount;
+ val.totalswap <<= bitcount;
+ val.freeswap <<= bitcount;
+ val.totalhigh <<= bitcount;
+ val.freehigh <<= bitcount;
+ }
+out:
if (copy_to_user(info, &val, sizeof(struct sysinfo)))
return -EFAULT;
return 0;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Mar 15 2001 - 21:00:10 EST