From 11d1cec1eeece689122022758b67396f875f901b Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Thu, 26 Jul 2012 14:42:58 -0700 Subject: [PATCH 2/3] ovsdb: Make "ovsdb-tool create" work through a dangling symlink. open() with O_CREAT|O_EXCL yields EEXIST if the name passed in is a symlink, but we would like "ovsdb-tool create /etc/openvswitch/conf.db" to work if /etc/openvswitch/conf.db is a symlink to elsewhere in the file system. This commit fixes the problem. It introduces a theoretical race, but no one should be doing "ovsdb-tool create" in parallel anyhow; O_EXCL is just an idiot check here, not required to be fail-safe. Debian bug #681880. CC: 681880@bugs.debian.org Reported-by: Bastian Blank Signed-off-by: Ben Pfaff --- ovsdb/log.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-) diff --git a/ovsdb/log.c b/ovsdb/log.c index ab4a150..9b882dc 100644 --- a/ovsdb/log.c +++ b/ovsdb/log.c @@ -95,7 +95,16 @@ ovsdb_log_open(const char *name, enum ovsdb_log_open_mode open_mode, } else if (open_mode == OVSDB_LOG_READ_WRITE) { flags = O_RDWR; } else if (open_mode == OVSDB_LOG_CREATE) { - flags = O_RDWR | O_CREAT | O_EXCL; + if (stat(name, &s) == -1 && errno == ENOENT + && lstat(name, &s) == 0 && S_ISLNK(s.st_mode)) { + /* 'name' is a dangling symlink. We want to create the file that + * the symlink points to, but POSIX says that open() with O_EXCL + * must fail with EEXIST if the named file is a symlink. So, we + * have to leave off O_EXCL and accept the race. */ + flags = O_RDWR | O_CREAT; + } else { + flags = O_RDWR | O_CREAT | O_EXCL; + } } else { NOT_REACHED(); } -- 1.7.2.5