> On 1 Dec 2022, at 21:19, Andrew Cooper <andrew.coop...@citrix.com> wrote:
>
> fallback_exception_handler feeds a string with embedded newlines directly into
> syslog(). While this is an improvement on getting nothing, syslogd escapes
> all control characters it gets, and emits one (long) line into the log.
>
> Fix the problem generally in the syslog stub. As we already have a local copy
> of the string, split it in place and emit one syslog() call per line.
>
> Also tweak Logging.msg_of to avoid putting an extra newline on a string which
> already ends with one.
>
> Fixes: ee7815f49faf ("tools/oxenstored: Set uncaught exception handler")
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> ---
> CC: Christian Lindig <christian.lin...@citrix.com>
> CC: David Scott <d...@recoil.org>
> CC: Edwin Torok <edvin.to...@citrix.com>
> CC: Rob Hoes <rob.h...@citrix.com>
Acked-by: Christian Lindig <christian.lin...@citrix.com>
> ---
> tools/ocaml/xenstored/logging.ml | 2 +-
> tools/ocaml/xenstored/syslog_stubs.c | 26 +++++++++++++++++++++++---
> 2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/tools/ocaml/xenstored/logging.ml
> b/tools/ocaml/xenstored/logging.ml
> index 255051437d60..f233bc9a3956 100644
> --- a/tools/ocaml/xenstored/logging.ml
> +++ b/tools/ocaml/xenstored/logging.ml
> @@ -344,7 +344,7 @@ let watch_not_fired ~con perms path =
> access_logging ~tid:0 ~con ~data Watch_not_fired ~level:Info
>
> let msg_of exn bt =
> - Printf.sprintf "Fatal exception: %s\n%s\n" (Printexc.to_string exn)
> + Printf.sprintf "Fatal exception: %s\n%s" (Printexc.to_string exn)
> (Printexc.raw_backtrace_to_string bt)
>
> let fallback_exception_handler exn bt =
> diff --git a/tools/ocaml/xenstored/syslog_stubs.c
> b/tools/ocaml/xenstored/syslog_stubs.c
> index e16c3a9491d0..760e78ff73dc 100644
> --- a/tools/ocaml/xenstored/syslog_stubs.c
> +++ b/tools/ocaml/xenstored/syslog_stubs.c
> @@ -37,14 +37,34 @@ value stub_syslog(value facility, value level, value msg)
> {
> CAMLparam3(facility, level, msg);
> char *c_msg = strdup(String_val(msg));
Is this working as expected? An OCaml string may contain embedded null bytes.
> + char *s = c_msg, *ss;
> int c_facility = __syslog_facility_table[Int_val(facility)]
> | __syslog_level_table[Int_val(level)];
>
> if ( !c_msg )
> caml_raise_out_of_memory();
> - caml_enter_blocking_section();
> - syslog(c_facility, "%s", c_msg);
> - caml_leave_blocking_section();
> +
> + /*
> + * syslog() doesn't like embedded newlines, and c_msg generally
> + * contains them.
> + *
> + * Split the message in place by converting \n to \0, and issue one
> + * syslog() call per line, skipping the final iteration if c_msg ends
> + * with a newline anyway.
> + */
> + do {
> + ss = strchr(s, '\n');
> + if ( ss )
> + *ss = '\0';
> + else if ( *s == '\0' )
> + break;
> +
> + caml_enter_blocking_section();
> + syslog(c_facility, "%s", s);
> + caml_leave_blocking_section();
> +
> + s = ss + 1;
> + } while ( ss );
>
> free(c_msg);
> CAMLreturn(Val_unit);
> --
> 2.11.0
>
