CVE-2022-50838

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: stream: purge sk_error_queue in sk_stream_kill_queues()

Changheon Lee reported TCP socket leaks, with a nice repro.

It seems we leak TCP sockets with the following sequence:

  1. SOF_TIMESTAMPING_TX_ACK is enabled on the socket.

    Each ACK will cook an skb put in error queue, from __skb_tstamp_tx(). __skb_tstamp_tx() is using skb_clone(), unless SOF_TIMESTAMPING_OPT_TSONLY was also requested.

  2. If the application is also using MSG_ZEROCOPY, then we put in the error queue cloned skbs that had a struct ubuf_info attached to them.

    Whenever an struct ubuf_info is allocated, sock_zerocopy_alloc() does a sock_hold().

    As long as the cloned skbs are still in sk_error_queue, socket refcount is kept elevated.

  3. Application closes the socket, while error queue is not empty.

Since tcp_close() no longer purges the socket error queue, we might end up with a TCP socket with at least one skb in error queue keeping the socket alive forever.

This bug can be (ab)used to consume all kernel memory and freeze the host.

We need to purge the error queue, with proper synchronization against concurrent writers.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux7737b104c211fa843de268b897d601e070292a72 < c8c1eec578a9ae2dc8f14a1846942a0b7bf29d1daffected
LinuxLinux89be5c357de34718eaaaefed80737f432c5ab86f < bab542cf56fc174c8447c00b73be99ffd66d2d39affected
LinuxLinux8b8b3d738e450d2c2ccdc75f0ab5a951746c2a96 < 6f00bd0402a1e3d2d556afba57c045bd7931e4d3affected
LinuxLinuxb631c603b5fb98d2bd709c35d384901965a3dd51 < 4f1d37ff4226eb99d6b69e9f4518e279e1a851bfaffected
LinuxLinuxdaf15fa1fd997749e881aedd9f03f73a11240e82 < 9062493811676ee0efe6c74d98f00ca38c4e17d4affected
LinuxLinux3988164fe9ddf98ebf5b5cdede91ac38c5f08a7e < 9da204cd67c4fe97e8aa465d10d5c2e7076f7f42affected
LinuxLinux24bcbe1cc69fa52dc4f7b5b2456678ed464724d8 < 8c330c36b3970d0917f48827fa6c7a9c75aa4602affected
LinuxLinux24bcbe1cc69fa52dc4f7b5b2456678ed464724d8 < b458d349f8753f666233828ebd30df6f100cf7d5affected
LinuxLinux24bcbe1cc69fa52dc4f7b5b2456678ed464724d8 < e0c8bccd40fc1c19e1d246c39bcf79e357e1ada3affected
LinuxLinux6ba975e14f5ebb87143d737c493adf4031409a68affected
LinuxLinux4437f3ead9e85c35fe0e3adfb98c0b97eaa267ebaffected
LinuxLinux4.9.291 < 4.9.337affected
LinuxLinux4.14.256 < 4.14.303affected
LinuxLinux4.19.218 < 4.19.270affected
LinuxLinux5.4.160 < 5.4.229affected
LinuxLinux5.10.80 < 5.10.163affected
LinuxLinux5.15.3 < 5.15.86affected
LinuxLinux4.4.293 < 4.5affected
LinuxLinux5.14.19 < 5.15affected
LinuxLinux5.16affected
LinuxLinux0 < 5.16unaffected
LinuxLinux4.9.337 <= 4.9.*unaffected
LinuxLinux4.14.303 <= 4.14.*unaffected
LinuxLinux4.19.270 <= 4.19.*unaffected
LinuxLinux5.4.229 <= 5.4.*unaffected
LinuxLinux5.10.163 <= 5.10.*unaffected
LinuxLinux5.15.86 <= 5.15.*unaffected
LinuxLinux6.0.16 <= 6.0.*unaffected
LinuxLinux6.1.2 <= 6.1.*unaffected
LinuxLinux6.2 <= *unaffected

Weaknesses

References