Calling VLOG_FATAL() while holding the 'log_file_mutex" may lead to
deadlock since VLOG_FATAL() implementation tries to acquire the
same lock. Fix this by building the error message first, then
call VLOG_FATAL() after the 'log_file_mutex' has been released.
This bug is not likely show up in practice since chown() usually
won't fail. It is still better to have a correct implementation.
Reported-by: Daniele Di Proietto <ddiproie...@vmware.com>
Signed-off-by: Andy Zhou <az...@nicira.com>
---
lib/vlog.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/lib/vlog.c b/lib/vlog.c
index a4aa2a0..28cea5d 100644
--- a/lib/vlog.c
+++ b/lib/vlog.c
@@ -438,15 +438,24 @@ vlog_reopen_log_file(void)
void
vlog_change_owner_unix(uid_t user, gid_t group)
{
- ovs_mutex_lock(&log_file_mutex);
- int error = log_file_name ? chown(log_file_name, user, group) : 0;
+ struct ds err = DS_EMPTY_INITIALIZER;
+ int error;
+ ovs_mutex_lock(&log_file_mutex);
+ error = log_file_name ? chown(log_file_name, user, group) : 0;
if (error) {
- VLOG_FATAL("Failed to change %s ownership: %s.",
- log_file_name, ovs_strerror(errno));
+ /* Build the error message. We can not call VLOG_FATAL directly
+ * here because VLOG_FATAL() will try again to to acquire
+ * 'log_file_mutex' lock, causing deadlock.
+ */
+ ds_put_format(&err, "Failed to change %s ownership: %s.",
+ log_file_name, ovs_strerror(errno));
}
-
ovs_mutex_unlock(&log_file_mutex);
+
+ if (error) {
+ VLOG_FATAL("%s", ds_steal_cstr(&err));
+ }
}
#endif
--
1.9.1
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