From: Jun'ichi Nomura 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: -------------------------------------------------------------------------- #!/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} -------------------------------------------------------------------------- Cc: stable@kernel.org Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon --- drivers/md/dm-ioctl.c | 10 +++------- drivers/md/dm-table.c | 7 ++++++- drivers/md/dm.c | 24 ++++++++++++++++++------ drivers/md/dm.h | 5 +++++ 4 files changed, 32 insertions(+), 14 deletions(-) Index: linux-2.6.24-rc5/drivers/md/dm-ioctl.c =================================================================== --- linux-2.6.24-rc5.orig/drivers/md/dm-ioctl.c 2007-12-12 15:40:33.000000000 +0000 +++ linux-2.6.24-rc5/drivers/md/dm-ioctl.c 2007-12-12 15:43:06.000000000 +0000 @@ -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 (!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); Index: linux-2.6.24-rc5/drivers/md/dm-table.c =================================================================== --- linux-2.6.24-rc5.orig/drivers/md/dm-table.c 2007-12-12 15:40:33.000000000 +0000 +++ linux-2.6.24-rc5/drivers/md/dm-table.c 2007-12-12 15:43:06.000000000 +0000 @@ -189,8 +189,10 @@ static int alloc_targets(struct dm_table /* * 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 @@ struct dm_target *dm_table_get_target(st /* * 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) { Index: linux-2.6.24-rc5/drivers/md/dm.c =================================================================== --- linux-2.6.24-rc5.orig/drivers/md/dm.c 2007-12-12 15:40:33.000000000 +0000 +++ linux-2.6.24-rc5/drivers/md/dm.c 2007-12-12 15:43:06.000000000 +0000 @@ -672,13 +672,19 @@ 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 (!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 @@ static void __clone_and_map(struct clone 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 @@ static void __clone_and_map(struct clone ci->idx++; } + + return 0; } /* @@ -767,6 +778,7 @@ static void __clone_and_map(struct clone 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 @@ static int __split_bio(struct mapped_dev 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; Index: linux-2.6.24-rc5/drivers/md/dm.h =================================================================== --- linux-2.6.24-rc5.orig/drivers/md/dm.h 2007-12-12 15:40:33.000000000 +0000 +++ linux-2.6.24-rc5/drivers/md/dm.h 2007-12-12 15:43:06.000000000 +0000 @@ -112,6 +112,11 @@ int dm_table_resume_targets(struct dm_ta 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. *---------------------------------------------------------------*/