Re: [PATCH] lib/vdso: Make clock_getres() POSIX compliant again

[Christophe Leroy]

Le 21/10/2019 à 12:07, Thomas Gleixner a écrit :

A recent commit removed the NULL pointer check from the clock_getres()
implementation causing a test case to fault.

POSIX requires an explicit NULL pointer check for clock_getres() aside of
the validity check of the clock_id argument for obscure reasons.

Add it back for both 32bit and 64bit.

Note, this is only a partial revert of the offending commit which does not
bring back the broken fallback invocation in the the 32bit compat
implementations of clock_getres() and clock_gettime().

Fixes: a9446a906f52 ("lib/vdso/32: Remove inconsistent NULL pointer checks")
Reported-by: Andreas Schwab <sch...@linux-m68k.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>

Tested-by: Christophe Leroy <christophe.le...@c-s.fr>

Cc: sta...@vger.kernel.org
---
  lib/vdso/gettimeofday.c |    9 +++++----
  1 file changed, 5 insertions(+), 4 deletions(-)

--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -214,9 +214,10 @@ int __cvdso_clock_getres_common(clockid_
                return -1;
        }

- res->tv_sec = 0;

-       res->tv_nsec = ns;
-
+       if (likely(res)) {
+               res->tv_sec = 0;
+               res->tv_nsec = ns;
+       }
        return 0;
  }

@@ -245,7 +246,7 @@ static __maybe_unused int

                ret = clock_getres_fallback(clock, &ts);
  #endif

- if (likely(!ret)) {

+       if (likely(!ret && res)) {
                res->tv_sec = ts.tv_sec;
                res->tv_nsec = ts.tv_nsec;
        }