Description of problem:
If libcall read(sysfd, buffer, sizeof(buffer) returns 0, it may lead to an underflow later in buffer[len - 1].

...snip...
248 static unsigned int
249 get_flags(char *module)
250 {
251         char    buffer[256], filename[256];
252         int     sysfd, len;
253
254         snprintf(filename, 256, "/proc/sys/sunrpc/%s_debug", module);
255
256         if ((sysfd = open(filename, O_RDONLY)) < 0) {
257                 perror(filename);
258                 exit(1);
259         }
260         if ((len = read(sysfd, buffer, sizeof(buffer))) < 0) {   // <- if len returns 0 here
261                 perror("read");
262                 exit(1);
263         }
264         close(sysfd);
265         buffer[len - 1] = '\0';    // <- buffer underflow
266
267         return strtoul(buffer, NULL, 0);
268 }
...snip...

Version-Release number of selected component (if applicable):
nfs-utils-2.5.4-18.el9