fat: allow time_offset to be up to 24 hours

Currently we limit values of time_offset mount option to be between -12
and 12 hours.  However e.g.  zone GMT+12 can have a DST correction on top
which makes the total time difference 13 hours.  Update the checks in
mount option parsing to allow offset of upto 24 hours to allow for unusual
cases.

Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Volker Kuhlmann <list0570@paradise.net.nz>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 6aece96df19fcebdda5ed3f036205bbaeddc65a6..3ac9078fde65f87ef3b434d21af0cb78211f3953 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1146,7 +1146,12 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
                case Opt_time_offset:
                        if (match_int(&args[0], &option))
                                return -EINVAL;
-                       if (option < -12 * 60 || option > 12 * 60)
+                       /*
+                        * GMT+-12 zones may have DST corrections so at least
+                        * 13 hours difference is needed. Make the limit 24
+                        * just in case someone invents something unusual.
+                        */
+                       if (option < -24 * 60 || option > 24 * 60)
                                return -EINVAL;
                        opts->tz_set = 1;
                        opts->time_offset = option;