logging: fix NULL pointer dereference in _output_buf()
In the _output_buf() we explicitly initialize only the 'buf' and 'len'
fields of the struct osmo_strbuf, leaving the 'pos' field implicitly
initialized to NULL. Later, in this function, 'sb.pos' is passed to
ctime_r() and strlen(), leading to a NULL pointer dereference (segfault)
in certain scenarios.
This situation can occur when color logging is disabled or when
a specific logging subsystem has no associated color. Any application
using libosmocore's logging API would crash with the following config:
log stderr
logging filter all 1
logging timestamp 1
logging color 0
Fix this by initializing the 'pos' field explicitly.
Change-Id: I7ec9badf525e03e54e10b725d820c636eaa3fd1c
Fixes: d71331bc "logging: fix nul octets in log output / use osmo_strbuf"
Fixes: CID#336550
diff --git a/src/core/logging.c b/src/core/logging.c
index 0d215f4..6941f9b 100644
--- a/src/core/logging.c
+++ b/src/core/logging.c
@@ -488,7 +488,7 @@
{
int ret;
const char *c_subsys = NULL;
- struct osmo_strbuf sb = { .buf = buf, .len = buf_len };
+ struct osmo_strbuf sb = { .buf = buf, .pos = buf, .len = buf_len };
/* safety net in case of encountering errors and returning nothing */
buf[0] = '\0';