dm: table detect io beyond device
This patch fixes a panic on shrinking a DM device if there is
outstanding I/O to the part of the device that is being removed.
(Normally this doesn't happen - a filesystem would be resized first,
for example.)
The bug is that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer. It may fail if a bio arrives from the
block layer but its target sector is no longer included in the DM
btree.
This patch appends an empty entry to table->targets[] which will
be returned by a lookup beyond the end of the device.
After calling dm_table_find_target(), __clone_and_map() and target_message()
check for this condition using
dm_target_is_valid().
Sample test script to trigger oops:
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 138200b..be730fd 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1250,21 +1250,17 @@
if (!table)
goto out_argv;
- if (tmsg->sector >= dm_table_get_size(table)) {
+ ti = dm_table_find_target(table, tmsg->sector);
+ if (!dm_target_is_valid(ti)) {
DMWARN("Target message sector outside device.");
r = -EINVAL;
- goto out_table;
- }
-
- ti = dm_table_find_target(table, tmsg->sector);
- if (ti->type->message)
+ } else if (ti->type->message)
r = ti->type->message(ti, argc, argv);
else {
DMWARN("Target type does not support messages");
r = -EINVAL;
}
- out_table:
dm_table_put(table);
out_argv:
kfree(argv);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index e298d8d..f3f952e 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -189,8 +189,10 @@
/*
* 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, sizeof(struct dm_target) +
+ n_highs = (sector_t *) dm_vcalloc(num + 1, sizeof(struct dm_target) +
sizeof(sector_t));
if (!n_highs)
return -ENOMEM;
@@ -867,6 +869,9 @@
/*
* Search the btree for the correct target.
+ *
+ * Caller should check returned pointer with dm_target_is_valid()
+ * to trap I/O beyond end of device.
*/
struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
{
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 07cbbb8..cff2a714 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -672,13 +672,19 @@
return clone;
}
-static void __clone_and_map(struct clone_info *ci)
+static int __clone_and_map(struct clone_info *ci)
{
struct bio *clone, *bio = ci->bio;
- struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
- sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
+ struct dm_target *ti;
+ sector_t len = 0, max;
struct dm_target_io *tio;
+ ti = dm_table_find_target(ci->map, ci->sector);
+ if (!dm_target_is_valid(ti))
+ return -EIO;
+
+ max = max_io_len(ci->md, ci->sector, ti);
+
/*
* Allocate a target io object.
*/
@@ -736,6 +742,9 @@
do {
if (offset) {
ti = dm_table_find_target(ci->map, ci->sector);
+ if (!dm_target_is_valid(ti))
+ return -EIO;
+
max = max_io_len(ci->md, ci->sector, ti);
tio = alloc_tio(ci->md);
@@ -759,6 +768,8 @@
ci->idx++;
}
+
+ return 0;
}
/*
@@ -767,6 +778,7 @@
static int __split_bio(struct mapped_device *md, struct bio *bio)
{
struct clone_info ci;
+ int error = 0;
ci.map = dm_get_table(md);
if (unlikely(!ci.map))
@@ -784,11 +796,11 @@
ci.idx = bio->bi_idx;
start_io_acct(ci.io);
- while (ci.sector_count)
- __clone_and_map(&ci);
+ while (ci.sector_count && !error)
+ error = __clone_and_map(&ci);
/* drop the extra reference count */
- dec_pending(ci.io, 0);
+ dec_pending(ci.io, error);
dm_table_put(ci.map);
return 0;
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 4b3faa4..177297a 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -112,6 +112,11 @@
int dm_table_any_congested(struct dm_table *t, int bdi_bits);
void dm_table_unplug_all(struct dm_table *t);
+/*
+ * To check the return value from dm_table_find_target().
+ */
+#define dm_target_is_valid(t) ((t)->table)
+
/*-----------------------------------------------------------------
* A registry of target types.
*---------------------------------------------------------------*/
