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 them. splice(2) reports an empty
record as EOF, and the caller tears down a connection that is still
live. recvmsg(2) makes no progress on one, so a peer that streams
them holds the caller in the kernel past SIGKILL. With MSG_PEEK or
async decryption, each record is also queued on rx_list, which
grows without bound.This series supersedes "[PATCH net] tls: skip empty data records in tls_sw_splice_read()", which fixes the splice case alone: https://lore.kernel.org/netdev/[email protected]/ Which fix a reader gets depends on its caller. splice(2) and recvmsg(2) are system calls, so consuming the record and testing signal_pending() is enough. A signal ends the call. Only tls_sw_read_sock() needs a bound of its own. Its callers hold the socket lock across the whole call and cannot act on a signal, so nothing else can stop the loop. A count of consecutive records that deliver no bytes supplies the bound (patch 1). The count is scoped to read_sock deliberately. A flood on the other two paths costs the caller CPU time and nothing else. The series changes user-visible behavior. splice(2) on a nonblocking socket, and sendfile(2) from one, now return -EAGAIN where they used to block, as they do on a plain TCP socket. A splice that reaches a control record behind an empty one now returns -EINVAL rather than the zero that was the false EOF. A nonblocking recvmsg(2) or splice(2) that has copied nothing and finds a signal pending after an empty record returns -EINTR. SO_RCVTIMEO does not bound these calls. It is applied at the reader lock and again on each call to tls_rx_rec_wait(), so a call that keeps retrying can wait past it. recvmsg(2) behaves this way today. The retry added to splice(2) extends the same behavior to that path. Tested on x86_64. The tls selftest suite passes, 935 tests with no skips. --- Changes in v2: - Bound no-data records by count, not elapsed time (Jakub). - Drop the tls_rx_empty_data_rec() helper (Sabrina). - Keep the strparser anchor out of tls_sw.c comments (Sabrina). - Split the recvmsg signal test into its own patch. - Drop tls_rx_intr_errno(); a nonblocking reader now gets -EINTR. - Say why do_splice() misses the socket's O_NONBLOCK (Sabrina). - Point the recvmsg patch's Fixes: at the commit that added rx_list. - Reuse the new zero_len helpers in the existing fixture (Sabrina). - Check errno unconditionally in the zero_len tests (Sabrina). - Split the splice crypto-error fix and its test out (Jakub): https://patch.msgid.link/[email protected] - Link to v1: https://patch.msgid.link/[email protected] --- Chuck Lever (8): tls: bound consecutive no-data records in tls_sw_read_sock() tls: check for a pending signal after an empty record tls: consume empty data records in tls_sw_splice_read() tls: honor O_NONBLOCK in tls_sw_splice_read() 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 net/tls/tls_sw.c | 78 ++++++++++-- tools/testing/selftests/net/tls.c | 255 +++++++++++++++++++++++++++++++++++--- 2 files changed, 306 insertions(+), 27 deletions(-) --- base-commit: f49defea7668d8c68ec19fa085ef3da6075561c7 change-id: 20260726-tls-follow-on-486f1ba8bbb0 Best regards, -- Chuck Lever <[email protected]>
