6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka <mpatocka@xxxxxxxxxx> [ Upstream commit f6007dce0cd35d634d9be91ef3515a6385dcee16 ] There's a race condition in the multipath target when retrieve_deps races with multipath_message calling dm_get_device and dm_put_device. retrieve_deps walks the list of open devices without holding any lock but multipath may add or remove devices to the list while it is running. The end result may be memory corruption or use-after-free memory access. See this description of a UAF with multipath_message(): https://listman.redhat.com/archives/dm-devel/2022-October/052373.html Fix this bug by introducing a new rw semaphore "devices_lock". We grab devices_lock for read in retrieve_deps and we grab it for write in dm_get_device and dm_put_device. Reported-by: Luo Meng <luomeng12@xxxxxxxxxx> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Tested-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/md/dm-core.h | 1 + drivers/md/dm-ioctl.c | 7 ++++++- drivers/md/dm-table.c | 32 ++++++++++++++++++++++++-------- 3 files changed, 31 insertions(+), 9 deletions(-) diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h index 28c641352de9b..71dcd8fd4050a 100644 --- a/drivers/md/dm-core.h +++ b/drivers/md/dm-core.h @@ -214,6 +214,7 @@ struct dm_table { /* a list of devices used by this table */ struct list_head devices; + struct rw_semaphore devices_lock; /* events get handed up using this callback */ void (*event_fn)(void *); diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 2afd2d2a0f407..206e6ce554dc7 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1566,6 +1566,8 @@ static void retrieve_deps(struct dm_table *table, struct dm_dev_internal *dd; struct dm_target_deps *deps; + down_read(&table->devices_lock); + deps = get_result_buffer(param, param_size, &len); /* @@ -1580,7 +1582,7 @@ static void retrieve_deps(struct dm_table *table, needed = struct_size(deps, dev, count); if (len < needed) { param->flags |= DM_BUFFER_FULL_FLAG; - return; + goto out; } /* @@ -1592,6 +1594,9 @@ static void retrieve_deps(struct dm_table *table, deps->dev[count++] = huge_encode_dev(dd->dm_dev->bdev->bd_dev); param->data_size = param->data_start + needed; + +out: + up_read(&table->devices_lock); } static int table_deps(struct file *filp, struct dm_ioctl *param, size_t param_size) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 288f600ee56dc..dac6a5f25f2be 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -134,6 +134,7 @@ int dm_table_create(struct dm_table **result, fmode_t mode, return -ENOMEM; INIT_LIST_HEAD(&t->devices); + init_rwsem(&t->devices_lock); if (!num_targets) num_targets = KEYS_PER_NODE; @@ -362,15 +363,19 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, return -ENODEV; } + down_write(&t->devices_lock); + dd = find_device(&t->devices, dev); if (!dd) { dd = kmalloc(sizeof(*dd), GFP_KERNEL); - if (!dd) - return -ENOMEM; + if (!dd) { + r = -ENOMEM; + goto unlock_ret_r; + } if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) { kfree(dd); - return r; + goto unlock_ret_r; } refcount_set(&dd->count, 1); @@ -380,12 +385,17 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { r = upgrade_mode(dd, mode, t->md); if (r) - return r; + goto unlock_ret_r; } refcount_inc(&dd->count); out: + up_write(&t->devices_lock); *result = dd->dm_dev; return 0; + +unlock_ret_r: + up_write(&t->devices_lock); + return r; } EXPORT_SYMBOL(dm_get_device); @@ -421,9 +431,12 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev, void dm_put_device(struct dm_target *ti, struct dm_dev *d) { int found = 0; - struct list_head *devices = &ti->table->devices; + struct dm_table *t = ti->table; + struct list_head *devices = &t->devices; struct dm_dev_internal *dd; + down_write(&t->devices_lock); + list_for_each_entry(dd, devices, list) { if (dd->dm_dev == d) { found = 1; @@ -432,14 +445,17 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d) } if (!found) { DMERR("%s: device %s not in table devices list", - dm_device_name(ti->table->md), d->name); - return; + dm_device_name(t->md), d->name); + goto unlock_ret; } if (refcount_dec_and_test(&dd->count)) { - dm_put_table_device(ti->table->md, d); + dm_put_table_device(t->md, d); list_del(&dd->list); kfree(dd); } + +unlock_ret: + up_write(&t->devices_lock); } EXPORT_SYMBOL(dm_put_device); -- 2.40.1
