[PATCH] make kernel warn about incorrectly sized partitions

Sometimes partitions claim to be larger than the reported capacity of a
disk device.  This patch makes the kernel warn about those partitions.

We still permit these patitions to be used.  Quoting Andries Brouwer
<Andries.Brouwer@cwi.nl>:

 Case 1: The kernel is mistaken about the size of the disk.  (There are
 commands to clip a disk to a certain capacity, there are jumpers to tell a
 disk that it should report a certain capacity etc.  Usually this is because
 of BIOS bugs.  In bad cases the machine will crash in the BIOS and hence fail
 to boot if the disk reports full capacity.) In such cases actually accessing
 the blocks of the partition may work fine, or may work fine after running an
 unclip utility.  I wrote "setmax" some years ago precisely for this reason.

 Case 2: There was a messy partition table (maybe just a rounding error) but
 the actual filesystem on the partition is contained in the physical disk.
 Now using the filesystem goes without problem.

 Case 3: Both partition and filesystem extend beyond the end of the disk.  In
 forensic or debugging situations one often uses a copy of the start of a
 disk.  Now access beyond the end gives an expected I/O error.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Stephen Cameron <steve.cameron@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index cd885b23cb5c..2ef313a96b66 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -484,6 +484,10 @@ int rescan_partitions(struct gendisk *disk, struct block_device *bdev)
                 sector_t from = state->parts[p].from;
                 if (!size)
                         continue;
+                if (from + size > get_capacity(disk)) {
+                        printk(" %s: p%d exceeds device capacity\n",
+                                disk->disk_name, p);
+                }
                 add_partition(disk, p, from, size);
 #ifdef CONFIG_BLK_DEV_MD
                 if (state->parts[p].flags)