From: Luo Meng <luomeng12@huawei.com> hulk inclusion category: bugfix bugzilla: 186184 CVE: NA -------------------------------- If dm_get_device() create dd in multipath_message(), and then call table_deps() after dm_put_table_device(), it will lead to concurrency UAF bugs. One of the concurrency UAF can be shown as below: (USE) | (FREE) | target_message | multipath_message | dm_put_device | dm_put_table_device # | kfree(td) # table_device *td ioctl # DM_TABLE_DEPS_CMD | ... table_deps | ... dm_get_live_or_inactive_table | ... retrieve_dep | ... list_for_each_entry | ... deps->dev[count++] = | ... huge_encode_dev | ... (dd->dm_dev->bdev->bd_dev) | list_del(&dd->list) | kfree(dd) # dm_dev_internal The root cause of UAF bugs is that find_device() failed in dm_get_device() and will create dd and refcount set 1, kfree() in dm_put_table() is not protected. When td, which there are still pointers point to, is released, the concurrency UAF bug will happen. This patch add a flag to determine whether to create a new dd. Signed-off-by: Luo Meng <luomeng12@huawei.com> Reviewed-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/md/dm-mpath.c | 2 +- drivers/md/dm-table.c | 43 +++++++++++++++++++++-------------- include/linux/device-mapper.h | 2 ++ 3 files changed, 29 insertions(+), 18 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index bced42f082b02..e0bfa16aab379 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -1962,7 +1962,7 @@ static int multipath_message(struct dm_target *ti, unsigned argc, char **argv, goto out; } - r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev); + r = __dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev, false); if (r) { DMWARN("message: error getting device %s", argv[1]); diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index 5c590895c14c3..f01c639f83875 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -361,12 +361,8 @@ dev_t dm_get_dev_t(const char *path) } EXPORT_SYMBOL_GPL(dm_get_dev_t); -/* - * Add a device to the list, or just increment the usage count if - * it's already present. - */ -int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, - struct dm_dev **result) +int __dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, + struct dm_dev **result, bool create_dd) { int r; dev_t dev; @@ -390,19 +386,21 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, dd = find_device(&t->devices, dev); if (!dd) { - dd = kmalloc(sizeof(*dd), GFP_KERNEL); - if (!dd) - return -ENOMEM; - - if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) { - kfree(dd); - return r; - } + if (create_dd) { + dd = kmalloc(sizeof(*dd), GFP_KERNEL); + if (!dd) + return -ENOMEM; - refcount_set(&dd->count, 1); - list_add(&dd->list, &t->devices); - goto out; + if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) { + kfree(dd); + return r; + } + refcount_set(&dd->count, 1); + list_add(&dd->list, &t->devices); + goto out; + } else + return -ENODEV; } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { r = upgrade_mode(dd, mode, t->md); if (r) @@ -413,6 +411,17 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, *result = dd->dm_dev; return 0; } +EXPORT_SYMBOL(__dm_get_device); + +/* + * Add a device to the list, or just increment the usage count if + * it's already present. + */ +int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, + struct dm_dev **result) +{ + return __dm_get_device(ti, path, mode, result, true); +} EXPORT_SYMBOL(dm_get_device); static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev, diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 50cc070cb1f7c..47db4a14c9258 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -162,6 +162,8 @@ dev_t dm_get_dev_t(const char *path); int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, struct dm_dev **result); void dm_put_device(struct dm_target *ti, struct dm_dev *d); +int __dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, + struct dm_dev **result, bool create_dd); /* * Information about a target type -- 2.25.1