From 1685e8ff7b86a4322153b65b7c56f3f8978ca077 Mon Sep 17 00:00:00 2001 From: Michal Lenc Date: Tue, 23 Jun 2026 09:28:41 +0200 Subject: [PATCH] syslog: avoid an infinite loop if one channel fails The current implementation exits syslog_write_foreach function if write to one channel fails, causing other channels not being written and returning negated errno. libc syslog functions then stay in an infinite loop, because error is returned and the same bytes are still passed to syslograwstream_flush and syslog_write_foreach. The channel write may fail for many reasons - disconnected USB if CDC ACM syslog is enabled, lost networking if telnet syslog is enabled, error on NOR flash etc. This shouldn't lead to an ininite loop in the code though. The solution ensures all channels in syslog_write_foreach are tried, therefore the user get the output to the working channels even if the first one is broken. It also updates syslograwstream_addchar and syslograwstream_addstring to skip the bytes if all channels fails. This ensures syslog call won't result in an infinite loop, but the user may lost the debugging output. Co-authored-by: Martin Krasula Signed-off-by: Michal Lenc --- drivers/syslog/syslog_write.c | 6 +++--- libs/libc/stream/lib_syslograwstream.c | 16 +++++++++++++--- 2 files changed, 16 insertions(+), 6 deletions(-) diff --git a/drivers/syslog/syslog_write.c b/drivers/syslog/syslog_write.c index 8b3fefda709..94e6c0d330e 100644 --- a/drivers/syslog/syslog_write.c +++ b/drivers/syslog/syslog_write.c @@ -107,7 +107,7 @@ ssize_t syslog_write_foreach(FAR const char *buffer, syslog_write_t write; syslog_putc_t putc; size_t nwritten = 0; - size_t nwritten_max = 0; + ssize_t nwritten_max = -EIO; ssize_t ret; int i; @@ -153,7 +153,7 @@ ssize_t syslog_write_foreach(FAR const char *buffer, if (ret < 0) { - return ret; + continue; } nwritten = head + 1; @@ -166,7 +166,7 @@ ssize_t syslog_write_foreach(FAR const char *buffer, ret = write(channel, buffer + nwritten, buflen - nwritten); if (ret < 0) { - return ret; + continue; } else { diff --git a/libs/libc/stream/lib_syslograwstream.c b/libs/libc/stream/lib_syslograwstream.c index 76b149f1d3a..270205f83a4 100644 --- a/libs/libc/stream/lib_syslograwstream.c +++ b/libs/libc/stream/lib_syslograwstream.c @@ -123,7 +123,12 @@ static void syslograwstream_addchar(FAR struct lib_syslograwstream_s *stream, /* Yes.. then flush the buffer */ - syslograwstream_flush(&stream->common); + int ret = syslograwstream_flush(&stream->common); + if (ret < 0) + { + stream->offset = 0; + stream->common.nput = 0; + } } } @@ -136,7 +141,6 @@ syslograwstream_addstring(FAR struct lib_syslograwstream_s *stream, FAR const char *buff, size_t len) { ssize_t ret = 0; - do { size_t remain = CONFIG_SYSLOG_BUFSIZE - stream->offset; @@ -155,7 +159,13 @@ syslograwstream_addstring(FAR struct lib_syslograwstream_s *stream, /* Yes.. then flush the buffer */ - syslograwstream_flush(&stream->common); + int ret_flush = syslograwstream_flush(&stream->common); + if (ret_flush < 0) + { + stream->offset = 0; + stream->common.nput = 0; + break; + } } } while (ret < len);