[PATCH 5.2 141/162] dm table: fix invalid memory accesses with too high sector number

Greg Kroah-Hartman
2019-08-27T08:06:06Z

From: Mikulas Patocka <mpatocka@redhat.com>

commit 1cfd5d3399e87167b7f9157ef99daa0e959f395d upstream.

If the sector number is too high, dm_table_find_target() should return a
pointer to a zeroed dm_target structure (the caller should test it with
dm_target_is_valid).

However, for some table sizes, the code in dm_table_find_target() that
performs btree lookup will access out of bound memory structures.

Fix this bug by testing the sector number at the beginning of
dm_table_find_target(). Also, add an "inline" keyword to the function
dm_table_get_size() because this is a hot path.

Fixes: 512875bd9661 ("dm: table detect io beyond device")
Cc: stable@vger.kernel.org
Reported-by: Zhang Tao <kontais@zoho.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-table.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1334,7 +1334,7 @@ void dm_table_event(struct dm_table *t)
}
EXPORT_SYMBOL(dm_table_event);

-sector_t dm_table_get_size(struct dm_table *t)
+inline sector_t dm_table_get_size(struct dm_table *t)
{
return t->num_targets ? (t->highs[t->num_targets - 1] + 1) : 0;
}
@@ -1359,6 +1359,9 @@ struct dm_target *dm_table_find_target(s
unsigned int l, n = 0, k = 0;
sector_t *node;

+ if (unlikely(sector >= dm_table_get_size(t)))
+ return &t->targets[t->num_targets];
+
for (l = 0; l < t->depth; l++) {
n = get_child(n, k);
node = get_node(t, l, n);