Work around Samba bug with ':' in symlink contents

* src/filelock.c (current_lock_owner): When reading the contents
of a lock, treat the UTF-8 for U+F022 as if it were ':' (Bug#24656).

1 files changed, 22 insertions, 13 deletions

diff --git a/src/filelock.c b/src/filelock.c
index a2e1df99f07..d4dfc1dd007 100644
--- a/src/filelock.c
+++ b/src/filelock.c
@@ -72,8 +72,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Normally use a symbolic link to represent a lock.
    The strategy: to lock a file FN, create a symlink .#FN in FN's
-   directory, with link data `user@host.pid'.  This avoids a single
-   mount (== failure) point for lock files.
+   directory, with link data USER@HOST.PID:BOOT.  This avoids a single
+   mount (== failure) point for lock files.  The :BOOT is omitted if
+   the boot time is not available.
 
    When the host in the lock data is the current host, we can check if
    the pid is valid with kill.
@@ -102,13 +103,11 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
    This is compatible with the locking scheme used by Interleaf (which
    has contributed this implementation for Emacs), and was designed by
-   Ethan Jacobson, Kimbo Mundy, and others.
-
-   --karl@cs.umb.edu/karl@hq.ileaf.com.
+   Karl Berry, Ethan Jacobson, Kimbo Mundy, and others.
 
    On some file systems, notably those of MS-Windows, symbolic links
-   do not work well, so instead of a symlink .#FN -> 'user@host.pid',
-   the lock is a regular file .#FN with contents 'user@host.pid'.  To
+   do not work well, so instead of a symlink .#FN -> USER@HOST.PID:BOOT,
+   the lock is a regular file .#FN with contents USER@HOST.PID:BOOT.  To
    establish a lock, a nonce file is created and then renamed to .#FN.
    On MS-Windows this renaming is atomic unless the lock is forcibly
    acquired.  On other systems the renaming is atomic if the lock is
@@ -289,8 +288,8 @@ enum { MAX_LFINFO = 8 * 1024 };
 
 typedef struct
 {
-  /* Location of '@', '.', ':' in USER.  If there's no colon, COLON
-     points to the end of USER.  */
+  /* Location of '@', '.', and ':' (or equivalent) in USER.  If there's
+     no colon or equivalent, COLON points to the end of USER.  */
   char *at, *dot, *colon;
 
   /* Lock file contents USER@HOST.PID with an optional :BOOT_TIME
@@ -548,7 +547,7 @@ current_lock_owner (lock_info_type *owner, char *lfname)
   if (!dot)
     return -1;
 
-  /* The PID is everything from the last `.' to the `:'.  */
+  /* The PID is everything from the last '.' to the ':' or equivalent.  */
   if (! c_isdigit (dot[1]))
     return -1;
   errno = 0;
@@ -556,7 +555,8 @@ current_lock_owner (lock_info_type *owner, char *lfname)
   if (errno == ERANGE)
     pid = -1;
 
-  /* After the `:', if there is one, comes the boot time.  */
+  /* After the ':' or equivalent, if there is one, comes the boot time.  */
+  char *boot = owner->colon + 1;
   switch (owner->colon[0])
     {
     case 0:
@@ -564,10 +564,19 @@ current_lock_owner (lock_info_type *owner, char *lfname)
       lfinfo_end = owner->colon;
       break;
 
+    case '\357':
+      /* Treat "\357\200\242" (U+F022 in UTF-8) as if it were ":".
+         This works around a bug in Samba, which can mistakenly
+         transliterate ':' to U+F022 in symlink contents (Bug#24656).
+         See <https://bugzilla.redhat.com/show_bug.cgi?id=1271407#c8>.  */
+      if (! (boot[0] == '\200' && boot[1] == '\242'))
+        return -1;
+      boot += 2;
+      /* Fall through.  */
     case ':':
-      if (! c_isdigit (owner->colon[1]))
+      if (! c_isdigit (boot[0]))
         return -1;
-      boot_time = strtoimax (owner->colon + 1, &lfinfo_end, 10);
+      boot_time = strtoimax (boot, &lfinfo_end, 10);
       break;
 
     default: