Commit 3be28e2c9cd0 ("net/tls: Consume empty data records in
tls_sw_read_sock()") fixed one reader. TLS 1.2 and TLS 1.3 both
permit a zero-length application_data record as a traffic-analysis
countermeasure (RFC 5246, Section 6.2.1; RFC 8446, Section 5.1), so
a peer that pads its stream emits them by design. The other two
software readers still mishandle one. splice(2) reports the empty
record as EOF and the caller tears down a connection that is still
live. recvmsg(2) neither advances nor returns, so a peer that
streams such records holds the caller in the kernel past SIGKILL
while rx_list grows without bound.
Which fix a reader gets depends on where it returns to. splice and
recvmsg return to userspace and drop the socket lock, so consuming
the record and testing signal_pending() is enough. read_sock runs
from kernel context and holds the lock across the whole call, so it
needs the return boundary a system call would otherwise supply: a
deadline armed by the first record that delivers no bytes and
disarmed by the first that delivers some (patch 1). Scoping that
cap to read_sock alone is deliberate, since a flood on the other
two paths costs the caller only its own scheduler time.
Two user-visible changes follow, both toward what a plain TCP
socket already does. splice(2) on a nonblocking socket, and
sendfile(2) from one, now return -EAGAIN where they used to block.
A splice that reaches a control record behind an empty one now
returns -EINVAL rather than the zero that was the false EOF.
No existing selftest variant reads a zero-length record back any
way but recv(2), so neither the splice path nor MSG_PEEK was
exercised against a record that decrypts to no payload. New
variants cover both.
---
Chuck Lever (9):
net/tls: Bound time spent on no-data records in tls_sw_read_sock()
net/tls: Consume empty data records in tls_sw_splice_read()
net/tls: Fail tls_sw_splice_read() after a failed async decrypt
net/tls: Honor O_NONBLOCK in tls_sw_splice_read()
net/tls: Consume empty data records in tls_sw_recvmsg()
selftests: tls: add peek and splice coverage for zero-length records
selftests: tls: skip the zero_len tests when TLS is unavailable
selftests: tls: cover splice on a nonblocking socket
selftests: tls: cover splice after a failed decrypt
net/tls/tls_sw.c | 113 +++++++++++--
tools/testing/selftests/net/tls.c | 322 ++++++++++++++++++++++++++++++++++++--
2 files changed, 414 insertions(+), 21 deletions(-)
---
base-commit: 53658c6f3682967a5e76ed4bc7462c4bdcddaec3
change-id: 20260726-tls-follow-on-486f1ba8bbb0
Best regards,
--
Chuck Lever <[email protected]>
