[glibc] linux: wait4: Fix incorrect return value comparison

[glibc] linux: wait4: Fix incorrect return value comparison

[Alistair Francis]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=00515ea3a15703a3d196c1d1bd372214abc990ad

commit 00515ea3a15703a3d196c1d1bd372214abc990ad
Author: Alistair Francis <alistair.francis@wdc.com>
Date:   Mon Apr 6 10:56:26 2020 -0700

    linux: wait4: Fix incorrect return value comparison
    
    Patch 600f00b "linux: Use long time_t for wait4/getrusage" introduced
    two bugs:
     - The usage32 struct was set if the wait4 syscall had an error.
     - For 32-bit systems the usage struct was set even if it was specified
       as NULL.
    
    This patch fixes the two issues.

Diff:
---
 sysdeps/unix/sysv/linux/wait4.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/wait4.c b/sysdeps/unix/sysv/linux/wait4.c
index d14bd4da27..44c55f60fe 100644
--- a/sysdeps/unix/sysv/linux/wait4.c
+++ b/sysdeps/unix/sysv/linux/wait4.c
@@ -29,13 +29,13 @@ __wait4_time64 (pid_t pid, int *stat_loc, int options, struct __rusage64 *usage)
 # if __KERNEL_OLD_TIMEVAL_MATCHES_TIMEVAL64
   return SYSCALL_CANCEL (wait4, pid, stat_loc, options, usage);
 # else
+  pid_t ret;
   struct __rusage32 usage32;
-  pid_t ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options, &usage32);
 
-  if (ret != 0)
-    return ret;
+  ret = SYSCALL_CANCEL (wait4, pid, stat_loc, options,
+                        usage != NULL ? &usage32 : NULL);
 
-  if (usage != NULL)
+  if (ret > 0 && usage != NULL)
     rusage32_to_rusage64 (&usage32, usage);
 
   return ret;
@@ -114,15 +114,14 @@ libc_hidden_def (__wait4_time64)
 pid_t
 __wait4 (pid_t pid, int *stat_loc, int options, struct rusage *usage)
 {
-  pid_t ret ;
+  pid_t ret;
   struct __rusage64 usage64;
 
-  ret = __wait4_time64 (pid, stat_loc, options, &usage64);
+  ret = __wait4_time64 (pid, stat_loc, options,
+                        usage != NULL ? &usage64 : NULL);
 
-  if (ret != 0)
-    return ret;
-
-  rusage64_to_rusage (&usage64, usage);
+  if (ret > 0 && usage != 0)
+    rusage64_to_rusage (&usage64, usage);
 
   return ret;
 }