From d01ffb9eee4af165d83b08dd73ebdf9fe94a519b Mon Sep 17 00:00:00 2001 From: Duoming Zhou Date: Fri, 28 Jan 2022 12:47:16 +0800 Subject: ax25: add refcount in ax25_dev to avoid UAF bugs If we dereference ax25_dev after we call kfree(ax25_dev) in ax25_dev_device_down(), it will lead to concurrency UAF bugs. There are eight syscall functions suffer from UAF bugs, include ax25_bind(), ax25_release(), ax25_connect(), ax25_ioctl(), ax25_getname(), ax25_sendmsg(), ax25_getsockopt() and ax25_info_show(). One of the concurrency UAF can be shown as below: (USE) | (FREE) | ax25_device_event | ax25_dev_device_down ax25_bind | ... ... | kfree(ax25_dev) ax25_fillin_cb() | ... ax25_fillin_cb_from_dev() | ... | The root cause of UAF bugs is that kfree(ax25_dev) in ax25_dev_device_down() is not protected by any locks. When ax25_dev, which there are still pointers point to, is released, the concurrency UAF bug will happen. This patch introduces refcount into ax25_dev in order to guarantee that there are no pointers point to it when ax25_dev is released. Signed-off-by: Duoming Zhou Signed-off-by: David S. Miller --- net/ax25/ax25_dev.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'net/ax25/ax25_dev.c') diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index 256fadb94df3..770b787fb7bb 100644 --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -37,6 +37,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr) for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next) if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) { res = ax25_dev; + ax25_dev_hold(ax25_dev); } spin_unlock_bh(&ax25_dev_lock); @@ -56,6 +57,7 @@ void ax25_dev_device_up(struct net_device *dev) return; } + refcount_set(&ax25_dev->refcount, 1); dev->ax25_ptr = ax25_dev; ax25_dev->dev = dev; dev_hold_track(dev, &ax25_dev->dev_tracker, GFP_ATOMIC); @@ -83,6 +85,7 @@ void ax25_dev_device_up(struct net_device *dev) spin_lock_bh(&ax25_dev_lock); ax25_dev->next = ax25_dev_list; ax25_dev_list = ax25_dev; + ax25_dev_hold(ax25_dev); spin_unlock_bh(&ax25_dev_lock); ax25_register_dev_sysctl(ax25_dev); @@ -112,20 +115,22 @@ void ax25_dev_device_down(struct net_device *dev) if ((s = ax25_dev_list) == ax25_dev) { ax25_dev_list = s->next; + ax25_dev_put(ax25_dev); spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put_track(dev, &ax25_dev->dev_tracker); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } while (s != NULL && s->next != NULL) { if (s->next == ax25_dev) { s->next = ax25_dev->next; + ax25_dev_put(ax25_dev); spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put_track(dev, &ax25_dev->dev_tracker); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } @@ -133,6 +138,7 @@ void ax25_dev_device_down(struct net_device *dev) } spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; + ax25_dev_put(ax25_dev); } int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) @@ -149,6 +155,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) if (ax25_dev->forward != NULL) return -EINVAL; ax25_dev->forward = fwd_dev->dev; + ax25_dev_put(fwd_dev); break; case SIOCAX25DELFWD: @@ -161,6 +168,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) return -EINVAL; } + ax25_dev_put(ax25_dev); return 0; } -- cgit v1.2.3