CVE-2021-47496: net/tls: Fix flipped sign in tls_err_abort() calls

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

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

sk->skerr 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] tlsencryptdone(..., err=<negative error from crypto request>) tlserrabort(.., err) sk->skerr = err;

[task] splicefrompipefeed ... tlsswdosendpage if (sk->skerr) { ret = -sk->skerr; // ret is positive

splicefrompipefeed (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 tlserrabort() 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.