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Subject[PATCH] fs/partitions/msdos.c Guard against negative sizes
Date
Hello Andries,

I've recently had a partly destroyed pc where the partition size was negative.
I was at that time running a dos recovery disk and having severe problems -
it would not boot.

So I had the idea of looking into the linux kernel to see how it would handle
these. I wrote some checks in fs/partitions/msdos.c.
I'm not sure if just dropping this partitions is the right thing to do - but
as I don't know what could break if there are wrong entries I propose the
following patch: (incomplete - should check in many more places)


If there is a better way of handling this I'd like to know.


Regards,

Phil



diff -u linux-2.5.59/fs/partitions/msdos.c.orig
linux-2.5.59/fs/partitions/msdos.c
--- linux-2.5.59/fs/partitions/msdos.c.orig Mon Jan 27 12:22:45 2003
+++ linux-2.5.59/fs/partitions/msdos.c Mon Jan 27 12:24:28 2003
@@ -133,6 +133,8 @@
these sometimes contain random garbage */
offs = START_SECT(p)*sector_size;
size = NR_SECTS(p)*sector_size;
+ if (size<0)
+ continue;
next = this_sector + offs;
if (i >= 2) {
if (offs + size > this_size)
@@ -423,7 +425,7 @@
for (slot = 1 ; slot <= 4 ; slot++, p++) {
u32 start = START_SECT(p)*sector_size;
u32 size = NR_SECTS(p)*sector_size;
- if (!size)
+ if (size <= 0)
continue;
if (is_extended_partition(p)) {
/* prevent someone doing mkfs or mkswap on an

-
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