From f3cdbe39b2ab0636dec0d5d43b54f1061ce7566c Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Wed, 17 May 2017 04:34:37 -0500 Subject: [PATCH] tcmu: fix crash during device removal We currently do tcmu_free_device ->tcmu_netlink_event(TCMU_CMD_REMOVED_DEVICE) -> uio_unregister_device -> kfree(tcmu_dev). The problem is that the kernel does not wait for userspace to do the close() on the uio device before freeing the tcmu_dev. We can then hit a race where the kernel frees the tcmu_dev before userspace does close() and so when close() -> release -> tcmu_release is done, we try to access a freed tcmu_dev. This patch made over the target-pending master branch moves the freeing of the tcmu_dev to when the last reference has been dropped. This also fixes a leak where if tcmu_configure_device was not called on a device we did not free udev->name which was allocated at tcmu_alloc_device time. Signed-off-by: Mike Christie Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_user.c | 46 ++++++++++++++++++++++++++++----------- 1 file changed, 33 insertions(+), 13 deletions(-) diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c index 9045837..beb5f09 100644 --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -97,7 +97,7 @@ struct tcmu_hba { struct tcmu_dev { struct list_head node; - + struct kref kref; struct se_device se_dev; char *name; @@ -969,6 +969,7 @@ static struct se_device *tcmu_alloc_device(struct se_hba *hba, const char *name) udev = kzalloc(sizeof(struct tcmu_dev), GFP_KERNEL); if (!udev) return NULL; + kref_init(&udev->kref); udev->name = kstrdup(name, GFP_KERNEL); if (!udev->name) { @@ -1145,6 +1146,24 @@ static int tcmu_open(struct uio_info *info, struct inode *inode) return 0; } +static void tcmu_dev_call_rcu(struct rcu_head *p) +{ + struct se_device *dev = container_of(p, struct se_device, rcu_head); + struct tcmu_dev *udev = TCMU_DEV(dev); + + kfree(udev->uio_info.name); + kfree(udev->name); + kfree(udev); +} + +static void tcmu_dev_kref_release(struct kref *kref) +{ + struct tcmu_dev *udev = container_of(kref, struct tcmu_dev, kref); + struct se_device *dev = &udev->se_dev; + + call_rcu(&dev->rcu_head, tcmu_dev_call_rcu); +} + static int tcmu_release(struct uio_info *info, struct inode *inode) { struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info); @@ -1152,7 +1171,8 @@ static int tcmu_release(struct uio_info *info, struct inode *inode) clear_bit(TCMU_DEV_BIT_OPEN, &udev->flags); pr_debug("close\n"); - + /* release ref from configure */ + kref_put(&udev->kref, tcmu_dev_kref_release); return 0; } @@ -1272,6 +1292,12 @@ static int tcmu_configure_device(struct se_device *dev) dev->dev_attrib.hw_max_sectors = 128; dev->dev_attrib.hw_queue_depth = 128; + /* + * Get a ref incase userspace does a close on the uio device before + * LIO has initiated tcmu_free_device. + */ + kref_get(&udev->kref); + ret = tcmu_netlink_event(TCMU_CMD_ADDED_DEVICE, udev->uio_info.name, udev->uio_info.uio_dev->minor); if (ret) @@ -1284,11 +1310,13 @@ static int tcmu_configure_device(struct se_device *dev) return 0; err_netlink: + kref_put(&udev->kref, tcmu_dev_kref_release); uio_unregister_device(&udev->uio_info); err_register: vfree(udev->mb_addr); err_vzalloc: kfree(info->name); + info->name = NULL; return ret; } @@ -1302,14 +1330,6 @@ static int tcmu_check_and_free_pending_cmd(struct tcmu_cmd *cmd) return -EINVAL; } -static void tcmu_dev_call_rcu(struct rcu_head *p) -{ - struct se_device *dev = container_of(p, struct se_device, rcu_head); - struct tcmu_dev *udev = TCMU_DEV(dev); - - kfree(udev); -} - static bool tcmu_dev_configured(struct tcmu_dev *udev) { return udev->uio_info.uio_dev ? true : false; @@ -1364,10 +1384,10 @@ static void tcmu_free_device(struct se_device *dev) udev->uio_info.uio_dev->minor); uio_unregister_device(&udev->uio_info); - kfree(udev->uio_info.name); - kfree(udev->name); } - call_rcu(&dev->rcu_head, tcmu_dev_call_rcu); + + /* release ref from init */ + kref_put(&udev->kref, tcmu_dev_kref_release); } enum { -- 2.7.4