[PATCH] block: atari: Return early for unsupported sector size

[PATCH] block: atari: Return early for unsupported sector size

[Gabriel Krisman Bertazi]

For 4K LBA or very large disks, atari_partition can easily get tricked
into thinking it has found an Atari partition table.  Depending on the
data in the disk, it ends up creating partitions with awkward lengths.

We saw logs like this while playing with fio.

[5.625867] nvme2n1: AHDI p2
[5.625872] nvme2n1: p2 size 2910030523 extends beyond EOD, truncated

People has had issues with misinterpreted AHDI partition tables for a long
time, see this BSD thread from 1995, for example.

https://mail-index.netbsd.org/port-atari/1995/11/19/0001.html

Since the atari partition, according to the spec, doesn't even support
sector sizes with more than 512, a quick sanity check is reasonable to
just bail out early, before even attempting to read sector 0.

Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
---
 block/partitions/atari.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/partitions/atari.c b/block/partitions/atari.c
index 9875b05..ff1fb93 100644
--- a/block/partitions/atari.c
+++ b/block/partitions/atari.c
@@ -42,6 +42,13 @@ int atari_partition(struct parsed_partitions *state)
 	int part_fmt = 0; /* 0:unknown, 1:AHDI, 2:ICD/Supra */
 #endif
 
+	/*
+	 * ATARI partition scheme supports 512 lba only.  If this is not
+	 * the case, bail early to avoid miscalculating hd_size.
+	 */
+	if (bdev_logical_block_size(state->bdev) != 512)
+		return 0;
+
 	rs = read_part_sector(state, 0, &sect);
 	if (!rs)
 		return -1;
-- 
2.1.0

Re: [PATCH] block: atari: Return early for unsupported sector size

[Gabriel Krisman Bertazi]

Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com> writes:

> For 4K LBA or very large disks, atari_partition can easily get tricked
> into thinking it has found an Atari partition table.  Depending on the
> data in the disk, it ends up creating partitions with awkward lengths.
>
> We saw logs like this while playing with fio.
>
> [5.625867] nvme2n1: AHDI p2
> [5.625872] nvme2n1: p2 size 2910030523 extends beyond EOD, truncated
>
> People has had issues with misinterpreted AHDI partition tables for a long
> time, see this BSD thread from 1995, for example.
>
> https://mail-index.netbsd.org/port-atari/1995/11/19/0001.html
>
> Since the atari partition, according to the spec, doesn't even support
> sector sizes with more than 512, a quick sanity check is reasonable to
> just bail out early, before even attempting to read sector 0.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
> ---

Hi Jens,

Any thoughts on this?  Do you think we can get it queued for 4.8?
-- 
Gabriel Krisman Bertazi

Re: [PATCH] block: atari: Return early for unsupported sector size

[Jens Axboe]

On 07/05/2016 09:38 AM, Gabriel Krisman Bertazi wrote:
> For 4K LBA or very large disks, atari_partition can easily get tricked
> into thinking it has found an Atari partition table.  Depending on the
> data in the disk, it ends up creating partitions with awkward lengths.
>
> We saw logs like this while playing with fio.
>
> [5.625867] nvme2n1: AHDI p2
> [5.625872] nvme2n1: p2 size 2910030523 extends beyond EOD, truncated
>
> People has had issues with misinterpreted AHDI partition tables for a long
> time, see this BSD thread from 1995, for example.
>
> https://mail-index.netbsd.org/port-atari/1995/11/19/0001.html
>
> Since the atari partition, according to the spec, doesn't even support
> sector sizes with more than 512, a quick sanity check is reasonable to
> just bail out early, before even attempting to read sector 0.

Added for 4.8, thanks.

-- 
Jens Axboe