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

From: Christophe Leroy
Date: Mon Oct 21 2019 - 11:23:46 EST




Le 21/10/2019 Ã 12:07, Thomas Gleixner a ÃcritÂ:
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 <schwab@xxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

Tested-by: Christophe Leroy <christophe.leroy@xxxxxx>

Cc: stable@xxxxxxxxxxxxxxx
---
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;
}