Hi
I tested it and the bug is real - with some table sizes,
dm_table_find_target will access memory out of bounds if the sector
argument is beyond limit.
Your patch fixes some of these cases, but not all of them.
I used this script to test all possible table sizes:
#!/bin/bash -e
sync
dmsetup remove_all || true
rmmod dm_mod || true
>t.txt
for i in `seq 1 10000`; do
echo $i
echo $((i-1)) 1 error >>t.txt
dmsetup create error <t.txt
dmsetup remove error
done
and I modified dm_table_find_target to call dm_table_find_target with too
high sector number. Without your patch, it fails on table with 16 entries;
with your patch applied, it fails on 144 entries.
I'll make another patch that passes the test.
Mikulas
On Wed, 21 Aug 2019, Zhang Tao wrote:
> From: Zhang Tao <zhangta...@lenovo.com>
>
> allocate num + 1 for target and offset array, n_highs need num + 1
> elements, the last element will be used for node lookup in function
> dm_table_find_target.
>
> Signed-off-by: Zhang Tao <zhangta...@lenovo.com>
> ---
> drivers/md/dm-table.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 7b6c3ee..fd7f604 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -160,20 +160,22 @@ static int alloc_targets(struct dm_table *t, unsigned
> int num)
> {
> sector_t *n_highs;
> struct dm_target *n_targets;
> + unsigned int alloc_num;
>
> /*
> * Allocate both the target array and offset array at once.
> * Append an empty entry to catch sectors beyond the end of
> * the device.
> */
> - n_highs = (sector_t *) dm_vcalloc(num + 1, sizeof(struct dm_target) +
> + alloc_num = num + 1;
> + n_highs = (sector_t *) dm_vcalloc(alloc_num, sizeof(struct dm_target) +
> sizeof(sector_t));
> if (!n_highs)
> return -ENOMEM;
>
> - n_targets = (struct dm_target *) (n_highs + num);
> + n_targets = (struct dm_target *) (n_highs + alloc_num);
>
> - memset(n_highs, -1, sizeof(*n_highs) * num);
> + memset(n_highs, -1, sizeof(*n_highs) * alloc_num);
> vfree(t->highs);
>
> t->num_allocated = num;
> --
> 1.8.3.1
>
>
> --
> dm-devel mailing list
> dm-de...@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>
