[CIFS] Fix setting time before epoch (negative time values)

[deliverable/linux.git] / fs / cifs / netmisc.c

diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
index 6834b9c3bec12505fe1adc55e17f911fef018eac..b333ff60781d295809d8fa8f23366f9bcf8d9285 100644 (file)
--- a/fs/cifs/netmisc.c
+++ b/fs/cifs/netmisc.c
@@ -925,11 +925,23 @@ cifs_NTtimeToUnix(__le64 ntutc)
        /* BB what about the timezone? BB */
 
        /* Subtract the NTFS time offset, then convert to 1s intervals. */
-       u64 t;
+       s64 t = le64_to_cpu(ntutc) - NTFS_TIME_OFFSET;
+
+       /*
+        * Unfortunately can not use normal 64 bit division on 32 bit arch, but
+        * the alternative, do_div, does not work with negative numbers so have
+        * to special case them
+        */
+       if (t < 0) {
+               t = -t;
+               ts.tv_nsec = (long)(do_div(t, 10000000) * 100);
+               ts.tv_nsec = -ts.tv_nsec;
+               ts.tv_sec = -t;
+       } else {
+               ts.tv_nsec = (long)do_div(t, 10000000) * 100;
+               ts.tv_sec = t;
+       }
 
-       t = le64_to_cpu(ntutc) - NTFS_TIME_OFFSET;
-       ts.tv_nsec = do_div(t, 10000000) * 100;
-       ts.tv_sec = t;
        return ts;
 }