@@ -959,10 +959,12 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
* If this is the last data and SPLICE_F_MORE was not set
* initially, clears it.
*/
- if (read_len < len)
- sd->flags |= SPLICE_F_MORE;
- else if (!more)
+ if (read_len < len) {
+ if (pos < i_size_read(file_inode(in)))
+ sd->flags |= SPLICE_F_MORE;
+ } else if (!more) {
sd->flags &= ~SPLICE_F_MORE;
+ }
/*
* NOTE: nonblocking mode only applies to the input. We
* must not do the output in nonblocking mode as then we
SPLICE_F_MORE should only get set if read_len < len and pos does not indicate file end. This is because the passed-in len can be greater than file size and read_len < len could indicate that end of file has been reached and there is no more pending data. ------ This issue was found during kTLS testing. Details as described in https://lists.openwall.net/netdev/2020/06/02/146 are below: When sendfile is used for kTLS file delivery and the size provided to sendfile via its 'count' parameter is greater than the file size, kTLS fails to send the file correctly. The last chunk of the file is not sent, and the data integrity of the file is compromised on the receiver side. Based on studying the sendfile source code, in such a case, last chunk of the file will be passed with the MSG_MORE flag set. Following snippet from fs/splice.c:1814 shows code within the while loop in splice_direct_to_actor() function that sets this flag: -------- /* * If more data is pending, set SPLICE_F_MORE * If this is the last data and SPLICE_F_MORE * was not set initially, clears it. */ if (read_len < len) sd->flags |= SPLICE_F_MORE; else if (!more) sd->flags &= ~SPLICE_F_MORE; -------- Due to this, tls layer adds the chunk to the pending records, but does not push it. Following lines of code from tls_sw_do_sendpage() function in tls_sw.c:1153 show the end of record (eor) variable being set based on MSG_MORE flag: -------- bool eor; eor = !(flags & (MSG_MORE | MSG_SENDPAGE_NOTLAST)); -------- This eor bool is then used in the condition check for full_record, end of record, or sk_msg_full in tls_sw_do_sendpage() function in tls_sw.c:1212: -------- if (full_record || eor || sk_msg_full(msg_pl)) { ret = bpf_exec_tx_verdict(msg_pl, sk, full_record, record_type, &copied, flags); if (ret) { if (ret == -EINPROGRESS) num_async++; else if (ret == -ENOMEM) goto wait_for_memory; else if (ret != -EAGAIN) { if (ret == -ENOSPC) ret = 0; goto sendpage_end; } } } continue; -------- Changing the code in splice_direct_to_actor() function in fs/splice.c to detect end of file by checking 'pos' variable against file size, and setting MSG_MORE flag only when EOF is not reached, fixes the issue: In splice_direct_to_actor():988: * If this is the last data and SPLICE_F_MORE was not set * initially, clears it. */ - if (read_len < len) - sd->flags |= SPLICE_F_MORE; - else if (!more) + if (read_len < len) { + if (pos < i_size_read(file_inode(in))) + sd->flags |= SPLICE_F_MORE; + } else if (!more) sd->flags &= ~SPLICE_F_MORE; + } ------- Here is the kTLS selftest that was submitted, and that helps reproduce the issue: https://lists.openwall.net/netdev/2020/06/05/109 ------- Signed-off-by: Pooja Trivedi <pooja.trivedi@stackpath.com> Signed-off-by: Mallesham Jatharkonda<mallesham.jatharkonda@oneconvergence.com> Signed-off-by: Josh Tway <josh.tway@stackpath.com> --- fs/splice.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)