dm table: fix invalid memory accesses with too high sector number

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>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5ac239d..29deda7 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1263,7 +1263,7 @@ 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;
 }
@@ -1288,6 +1288,9 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
        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);