CVE-2021-47496 Information

Description

In the Linux kernel the following vulnerability has been resolved:

net/tls: Fix flipped sign in tls_err_abort() calls

sk->sk_err appears to expect a positive value a convention that ktls doesn’t always follow and that leads to memory corruption in other code. For instance

[kworker]
tls_encrypt_done(... err=<negative error from crypto request>)
  tls_err_abort(.. err)
    sk->sk_err = err;

[task]
splice_from_pipe_feed
  ...
    tls_sw_do_sendpage
      if (sk->sk_err) 
        ret = -sk->sk_err;  // ret is positive

splice_from_pipe_feed (continued)
  ret = actor(...)  // ret is still positive and interpreted as bytes
                    // written resulting in underflow of buf->len and
                    // sd->len leading to huge buf->offset and bogus
                    // addresses computed in later calls to actor()

Fix all tls_err_abort() callers to pass a negative error code consistently and centralize the error-prone sign flip there throwing in a warning to catch future misuse and uninlining the function so it really does only warn once.

Reference

https://git.kernel.org/stable/c/e0cfd5159f314d6b304d030363650b06a2299cbb https://git.kernel.org/stable/c/f3dec7e7ace38224f82cf83f0049159d067c2e19 https://git.kernel.org/stable/c/e41473543f75f7dbc5d605007e6f883f1bd13b9a https://git.kernel.org/stable/c/da353fac65fede6b8b4cfe207f0d9408e3121105