fs/partition/msdos: fix unusable extended partition for > 512B sector

Smaller size than a minimum blocksize can't be used, after all it's
handled like 0 size.

For extended partition itself, this makes sure to use bigger size than one
logical sector size at least.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Daniel Taylor <Daniel.Taylor@wdc.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/fs/partitions/msdos.c b/fs/partitions/msdos.c
index b78385840a55..90be97f1f5a8 100644
--- a/fs/partitions/msdos.c
+++ b/fs/partitions/msdos.c
@@ -492,9 +492,16 @@ int msdos_partition(struct parsed_partitions *state, struct block_device *bdev)
                 if (!size)
                         continue;
                 if (is_extended_partition(p)) {
-                        /* prevent someone doing mkfs or mkswap on an
-                           extended partition, but leave room for LILO */
-                        put_partition(state, slot, start, size == 1 ? 1 : 2);
+                        /*
+                         * prevent someone doing mkfs or mkswap on an
+                         * extended partition, but leave room for LILO
+                         * FIXME: this uses one logical sector for > 512b
+                         * sector, although it may not be enough/proper.
+                         */
+                        sector_t n = 2;
+                        n = min(size, max(sector_size, n));
+                        put_partition(state, slot, start, n);
+
                         printk(" <");
                         parse_extended(state, bdev, start, size);
                         printk(" >");