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 <[EMAIL PROTECTED]> --- 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); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/