(rpl_chown) [CHOWN_MODIFIES_SYMLINK]:

Don't try O_WRONLY unless O_RDONLY failed wth EACCES.
Fall back on chown if open failed with EACCES.

1 files changed, 27 insertions, 10 deletions

diff --git a/lib/chown.c b/lib/chown.c
index 729dd3b0b..2a7bba1a6 100644
--- a/lib/chown.c
+++ b/lib/chown.c
@@ -27,12 +27,15 @@
    most systems.  */
 #undef chown
 
+#include <stdbool.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
 
+#include "stat-macros.h"
+
 /* Provide a more-closely POSIX-conforming version of chown on
    systems with one or both of the following problems:
    - chown doesn't treat an ID of -1 as meaning
@@ -66,20 +69,34 @@ rpl_chown (const char *file, uid_t uid, gid_t gid)
        on the symlink itself.  To work around that, we open the
        file (but this can fail due to lack of read or write permission) and
        use fchown on the resulting descriptor.  */
-    int fd = open (file, O_RDONLY | O_NONBLOCK | O_NOCTTY);
-    if (fd < 0
-	&& (fd = open (file, O_WRONLY | O_NONBLOCK | O_NOCTTY)) < 0)
-      return -1;
-    if (fchown (fd, uid, gid))
+    int open_flags = O_NONBLOCK | O_NOCTTY;
+    int fd = open (file, O_RDONLY | open_flags);
+    if (0 <= fd
+	|| (errno == EACCES
+	    && 0 <= (fd = open (file, O_WRONLY | open_flags))))
       {
+	int result = fchown (fd, uid, gid);
 	int saved_errno = errno;
+
+	/* POSIX says fchown can fail with errno == EINVAL on sockets,
+	   so fall back on chown in that case.  */
+	struct stat sb;
+	bool fchown_socket_failure =
+	  (result != 0 && saved_errno == EINVAL
+	   && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
+
 	close (fd);
-	errno = saved_errno;
-	return -1;
+
+	if (! fchown_socket_failure)
+	  {
+	    errno = saved_errno;
+	    return result;
+	  }
       }
-    return close (fd);
+    else if (errno != EACCES)
+      return -1;
   }
-#else
-  return chown (file, uid, gid);
 #endif
+
+  return chown (file, uid, gid);
 }