[PATCH v2] xfs_repair: detect null buf passed to duration

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

gcc 12.2 with ubsan and fortify turned on complains about this:

In file included from /usr/include/stdio.h:906,
                 from ../include/platform_defs.h:9,
                 from ../include/libxfs.h:16,
                 from progress.c:3:
In function ‘sprintf’,
    inlined from ‘duration’ at progress.c:443:4:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:30:10: error: null destination pointer [-Werror=format-overflow=]
   30 |   return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   31 |                                   __glibc_objsize (__s), __fmt,
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   32 |                                   __va_arg_pack ());
      |                                   ~~~~~~~~~~~~~~~~~

I think this is a false negative since all callers are careful not to
pass in a null pointer.  Unfortunately the compiler cannot detect that
since this isn't a static function and complains.  Fix this by adding an
explicit declaration that buf isn't null.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 repair/progress.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/repair/progress.h b/repair/progress.h
index 0b06b2c4f43f..c09aa69413ac 100644
--- a/repair/progress.h
+++ b/repair/progress.h
@@ -38,7 +38,7 @@ extern void summary_report(void);
 extern int  set_progress_msg(int report, uint64_t total);
 extern uint64_t print_final_rpt(void);
 extern char *timestamp(struct xfs_mount *mp, int end, int phase, char *buf);
-extern char *duration(time_t val, char *buf);
+char *duration(time_t val, char *buf) __attribute__((nonnull(2)));
 extern int do_parallel;
 
 #define	PROG_RPT_INC(a,b) if (ag_stride && prog_rpt_done) (a) += (b)