sysctl: Don't crash file fopen fails

The commit referenced below put a setvbuf() before checking what
fopen() returned. If the file could not be opened then the file
handle was NULL at setvbuf() crashed.

setvbuf() is now called after checking what fopen() returns and only
when it was successful.

References:
 procps-ng/procps#76
 commit 58ae084c2737cdee395915d45dbcb364648ac615

diff --git a/NEWS b/NEWS
index 251a1fec1c35c39647791f157cf9df48c69fed88..7ffe74a9cc8db7d3875c55df0dc4c293d262a462 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,7 @@ procps-ng-NEXT
   * ps: recognizes SCHED_DEADLINE as valid CPU scheduler
   * ps: display NUMA node under which a thread ran         issue #58
   * sysctl: Permit empty string for value                  issue #74
+  * sysctl: Don't segv when file not available             issue #76
   * top: add config file support for XDG specification
   * top: eliminated minor libnuma memory leak
   * top: show fewer memory decimal places (configurable)   issue #50

diff --git a/sysctl.c b/sysctl.c
index 834662b34b40a808876ef637ae7fdfae95aeadf5..7c05243d6c307d04dc47e16abeaf6ad87e05e2f4 100644 (file)
--- a/sysctl.c
+++ b/sysctl.c
@@ -222,9 +222,6 @@ static int ReadSetting(const char *restrict const name)
 
        fp = fopen(tmpname, "r");
 
-       if (iobuf)
-               setvbuf(fp, iobuf, _IOFBF, IOBUFSIZ);
-
        if (!fp) {
                switch (errno) {
                case ENOENT:
@@ -246,6 +243,9 @@ static int ReadSetting(const char *restrict const name)
                        break;
                }
        } else {
+           if (iobuf)
+            setvbuf(fp, iobuf, _IOFBF, IOBUFSIZ);
+
                errno = 0;
                if (fgets(inbuf, sizeof inbuf - 1, fp)) {
                        /* this loop is required, see