Re: dm stripe: Fix bounds

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This patch broke my system. I am booting from a hardware fakeraid consisting of a raid-0 between two WD 36 gig 10,000 rpm raptors on a VIA sata raid controller. The dmraid utility previously would correctly configure dm to access the device ( though I did see some of the IO errors you mention in my logs ) and now dmraid fails to configure the dm table because this patch rejects it. My working dmraid table follows:

via_hfciifae: 0 144607678 striped 2 128 8:0 0 8:16 0

I believe the correct thing to do is to special case the last stripe in the volume like such:

0-31    64-67
32-63   68-71

Alasdair G Kergon wrote:
From: Kevin Corry <[email protected]>

The dm-stripe target currently does not enforce that the size of a stripe device be a multiple of the chunk-size. Under certain conditions, this can lead to I/O requests going off the end of an underlying device. This test-case shows one example.

echo "0 100 linear /dev/hdb1 0" | dmsetup create linear0
echo "0 100 linear /dev/hdb1 100" | dmsetup create linear1
echo "0 200 striped 2 32 /dev/mapper/linear0 0 /dev/mapper/linear1 0" | \
   dmsetup create stripe0
dd if=/dev/zero of=/dev/mapper/stripe0 bs=1k

This will produce the output:
dd: writing '/dev/mapper/stripe0': Input/output error
97+0 records in
96+0 records out

And in the kernel log will be:
attempt to access beyond end of device
dm-0: rw=0, want=104, limit=100

The patch below will check that the table size is a multiple of the stripe chunk-size when the table is created, which will prevent the above striped device from being created.

This should not affect tools like LVM or EVMS, since in all the cases I can think of, striped devices are always created with the sizes being a multiple of the chunk-size.

The size of a stripe device must be a multiple of its chunk-size.

Signed-off-by: Kevin Corry <[email protected]>
Signed-Off-By: Alasdair G Kergon <[email protected]>

 dm-stripe.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-2.6.16-rc5/drivers/md/dm-stripe.c
===================================================================
--- linux-2.6.16-rc5.orig/drivers/md/dm-stripe.c	2006-03-14 18:25:38.000000000 +0000
+++ linux-2.6.16-rc5/drivers/md/dm-stripe.c	2006-03-15 17:56:37.000000000 +0000
@@ -103,9 +103,15 @@ static int stripe_ctr(struct dm_target *
 		return -EINVAL;
 	}
+ if (((uint32_t)ti->len) & (chunk_size - 1)) {
+		ti->error = "dm-stripe: Target length not divisible by "
+		    "chunk size";
+		return -EINVAL;
+	}
+
 	width = ti->len;
 	if (sector_div(width, stripes)) {
-		ti->error = "dm-stripe: Target length not divisable by "
+		ti->error = "dm-stripe: Target length not divisible by "
 		    "number of stripes";
 		return -EINVAL;
 	}

-
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