From: Duoming Zhou duoming@zju.edu.cn
commit d01ffb9eee4af165d83b08dd73ebdf9fe94a519b upstream.
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 duoming@zju.edu.cn Signed-off-by: David S. Miller davem@davemloft.net [OP: backport to 4.19: adjusted context] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/ax25.h | 10 ++++++++++ net/ax25/af_ax25.c | 2 ++ net/ax25/ax25_dev.c | 12 ++++++++++-- net/ax25/ax25_route.c | 3 +++ 4 files changed, 25 insertions(+), 2 deletions(-)
--- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -236,6 +236,7 @@ typedef struct ax25_dev { #if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER) ax25_dama_info dama; #endif + refcount_t refcount; } ax25_dev;
typedef struct ax25_cb { @@ -290,6 +291,15 @@ static __inline__ void ax25_cb_put(ax25_ } }
+#define ax25_dev_hold(__ax25_dev) \ + refcount_inc(&((__ax25_dev)->refcount)) + +static __inline__ void ax25_dev_put(ax25_dev *ax25_dev) +{ + if (refcount_dec_and_test(&ax25_dev->refcount)) { + kfree(ax25_dev); + } +} static inline __be16 ax25_type_trans(struct sk_buff *skb, struct net_device *dev) { skb->dev = dev; --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -101,6 +101,7 @@ again: spin_unlock_bh(&ax25_list_lock); lock_sock(sk); s->ax25_dev = NULL; + ax25_dev_put(ax25_dev); release_sock(sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); @@ -449,6 +450,7 @@ static int ax25_ctl_ioctl(const unsigned }
out_put: + ax25_dev_put(ax25_dev); ax25_cb_put(ax25); return ret;
--- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -40,6 +40,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next) if (ax25cmp(addr, (ax25_address *)ax25_dev->dev->dev_addr) == 0) { res = ax25_dev; + ax25_dev_hold(ax25_dev); } spin_unlock_bh(&ax25_dev_lock);
@@ -59,6 +60,7 @@ void ax25_dev_device_up(struct net_devic return; }
+ refcount_set(&ax25_dev->refcount, 1); dev->ax25_ptr = ax25_dev; ax25_dev->dev = dev; dev_hold(dev); @@ -86,6 +88,7 @@ void ax25_dev_device_up(struct net_devic 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); @@ -115,20 +118,22 @@ void ax25_dev_device_down(struct net_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(dev); - 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(dev); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; }
@@ -136,6 +141,7 @@ void ax25_dev_device_down(struct net_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) @@ -152,6 +158,7 @@ int ax25_fwd_ioctl(unsigned int cmd, str if (ax25_dev->forward != NULL) return -EINVAL; ax25_dev->forward = fwd_dev->dev; + ax25_dev_put(fwd_dev); break;
case SIOCAX25DELFWD: @@ -164,6 +171,7 @@ int ax25_fwd_ioctl(unsigned int cmd, str return -EINVAL; }
+ ax25_dev_put(ax25_dev); return 0; }
--- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -119,6 +119,7 @@ static int __must_check ax25_rt_add(stru ax25_rt->dev = ax25_dev->dev; ax25_rt->digipeat = NULL; ax25_rt->ip_mode = ' '; + ax25_dev_put(ax25_dev); if (route->digi_count != 0) { if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) { write_unlock_bh(&ax25_route_lock); @@ -175,6 +176,7 @@ static int ax25_rt_del(struct ax25_route } } } + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock);
return 0; @@ -217,6 +219,7 @@ static int ax25_rt_opt(struct ax25_route }
out: + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock); return err; }