Fix 'zdb -o' segmentation fault

Fix a regression accidentally introduced by OpenZFS 7280 in ed828c0: since
whether to accept NULL as a valid first parameter in strchr() is implementation
specific we add an additional check to avoid crashing.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #5917

diff --git a/lib/libzpool/util.c b/lib/libzpool/util.c
index 3bdc3172298117ba835d3adc82252d9845313ef2..8e1c104a3d516511778fb90b4a3ff69f22ae1e0a 100644 (file)
--- a/lib/libzpool/util.c
+++ b/lib/libzpool/util.c
@@ -182,7 +182,7 @@ set_global_var(char *arg)
            "little-endian systems\n");
        return (ENOTSUP);
 #endif
-       if ((varval = strchr(arg, '=')) != NULL) {
+       if (arg != NULL && (varval = strchr(arg, '=')) != NULL) {
                *varval = '\0';
                varval++;
                val = strtoull(varval, NULL, 0);