In afalg_stream, if the stream refers to a regular file, and sendfile() fails, do we have a guarantee that the offset of the file descriptor remains unchanged?
The man page at http://man7.org/linux/man-pages/man2/sendfile.2.html doesn't say so. How about this, then? Does this look right? 2018-06-24 Bruno Haible <br...@clisp.org> af_alg: Fix error handling after sendfile() fails. * lib/af_alg.c (afalg_stream): Don't make assumptions about fd's position after a sendfile() failure. diff --git a/lib/af_alg.c b/lib/af_alg.c index 33d8837..3edcdf3 100644 --- a/lib/af_alg.c +++ b/lib/af_alg.c @@ -120,7 +120,11 @@ afalg_stream (FILE *stream, const char *alg, && off < st.st_size && st.st_size - off < SYS_BUFSIZE_MAX) { off_t nbytes = st.st_size - off; - result = sendfile (ofd, fd, &off, nbytes) == nbytes ? 0 : -EAFNOSUPPORT; + if (sendfile (ofd, fd, &off, nbytes) == nbytes) + result = 0; + else + /* Attempt to reposition fd to where it was. */ + result = (fseeko (stream, off, SEEK_SET) == 0 ? -EAFNOSUPPORT : -EIO); } else {
