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authorDuoming Zhou <duoming@zju.edu.cn>2022-01-28 12:47:16 +0800
committerDavid S. Miller <davem@davemloft.net>2022-01-28 14:56:47 +0000
commitd01ffb9eee4af165d83b08dd73ebdf9fe94a519b (patch)
treeae3be0b158b4a7dfb2162956ca6b63f22a3eb6c2 /net/ax25/af_ax25.c
parent4e0f718daf97d47cf7dec122da1be970f145c809 (diff)
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 <duoming@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ax25/af_ax25.c')
-rw-r--r--net/ax25/af_ax25.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 44a8730c26ac..32f61978ff29 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -91,6 +91,7 @@ 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);
@@ -439,6 +440,7 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg)
}
out_put:
+ ax25_dev_put(ax25_dev);
ax25_cb_put(ax25);
return ret;