Hi,
This patch fixes a panic on shrinking DM device, due to reference
outside of the DM table.
The problem occurs only if there is outstanding I/O to the removed
part of the device.
The bug is in that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer.
It may fail if a BIO is sent from the block layer but its target
sector is already not in the DM table.
This patch tidies up dm_table_find_target() to return NULL
instead of bogus pointer for failure case.
Then __clone_and_map() can check the return value of it
and make the BIO return with -EIO.
target_message() in dm-ioctl.c, the only other user of
dm_table_find_target(), is modified to use the return value of it, too.
Sample test script to trigger oops:
--------------------------------------------------------------------------
#!/bin/bash
FILE=$(mktemp)
LODEV=$(losetup -f)
MAP=$(basename ${FILE})
SIZE=4M
dd if=/dev/zero of=${FILE} bs=${SIZE} count=1
losetup ${LODEV} ${FILE}
echo "0 $(blockdev --getsz ${LODEV}) linear ${LODEV} 0" |dmsetup create ${MAP}
dmsetup suspend ${MAP}
echo "0 1 linear ${LODEV} 0" |dmsetup load ${MAP}
dd if=/dev/zero of=/dev/mapper/${MAP} bs=${SIZE} count=1 &
echo "Wait til dd push some I/O"
sleep 5
dmsetup resume ${MAP}
--------------------------------------------------------------------------
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
---
dm-ioctl.c | 10 +++-------
dm-table.c | 3 +++
dm.c | 24 ++++++++++++++++++------
3 files changed, 24 insertions(+), 13 deletions(-)
Index: linux-2.6.23.work/drivers/md/dm.c
===================================================================
--- linux-2.6.23.work.orig/drivers/md/dm.c
+++ linux-2.6.23.work/drivers/md/dm.c
@@ -663,13 +663,19 @@ static struct bio *clone_bio(struct bio
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 (!ti)
+ return -EIO;
+
+ max = max_io_len(ci->md, ci->sector, ti);
+
/*
* Allocate a target io object.
*/
@@ -727,6 +733,9 @@ static void __clone_and_map(struct clone
do {
if (offset) {
ti = dm_table_find_target(ci->map, ci->sector);
+ if (!ti)
+ return -EIO;
+
max = max_io_len(ci->md, ci->sector, ti);
tio = alloc_tio(ci->md);
@@ -750,6 +759,8 @@ static void __clone_and_map(struct clone
ci->idx++;
}
+
+ return 0;
}
/*
@@ -758,6 +769,7 @@ static void __clone_and_map(struct clone
static void __split_bio(struct mapped_device *md, struct bio *bio)
{
struct clone_info ci;
+ int error = 0;
ci.map = dm_get_table(md);
if (!ci.map) {
@@ -777,11 +789,11 @@ static void __split_bio(struct mapped_de
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);
}
/*-----------------------------------------------------------------
Index: linux-2.6.23.work/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6.23.work.orig/drivers/md/dm-ioctl.c
+++ linux-2.6.23.work/drivers/md/dm-ioctl.c
@@ -1250,21 +1250,17 @@ static int target_message(struct dm_ioct
if (!table)
goto out_argv;
- if (tmsg->sector >= dm_table_get_size(table)) {
+ ti = dm_table_find_target(table, tmsg->sector);
+ if (!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);
Index: linux-2.6.23.work/drivers/md/dm-table.c
===================================================================
--- linux-2.6.23.work.orig/drivers/md/dm-table.c
+++ linux-2.6.23.work/drivers/md/dm-table.c
@@ -868,6 +868,9 @@ struct dm_target *dm_table_find_target(s
unsigned int l, n = 0, k = 0;
sector_t *node;
+ if (sector >= dm_table_get_size(t))
+ return NULL;
+
for (l = 0; l < t->depth; l++) {
n = get_child(n, k);
node = get_node(t, l, n);
--
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