CID 337783: Avoid passing -1 to read

diff --git a/src/magic.c b/src/magic.c
index 2207f083466f79467ba578cbf7c918bfb76987a1..0796a753a819491091e9d0a9cb1c8f007833132a 100644 (file)
--- a/src/magic.c
+++ b/src/magic.c
@@ -33,7 +33,7 @@
 #include "file.h"
 
 #ifndef        lint
-FILE_RCSID("@(#)$File: magic.c,v 1.109 2019/02/20 02:35:27 christos Exp $")
+FILE_RCSID("@(#)$File: magic.c,v 1.110 2019/04/15 16:49:29 christos Exp $")
 #endif /* lint */
 
 #include "magic.h"
@@ -472,12 +472,14 @@ file_or_fd(struct magic_set *ms, const char *inname, int fd)
         * try looking at the first ms->bytes_max bytes
         */
        if (ispipe) {
-               ssize_t r = 0;
+               if (fd != -1) {
+                       ssize_t r = 0;
 
-               while ((r = sread(fd, RCAST(void *, &buf[nbytes]),
-                   CAST(size_t, ms->bytes_max - nbytes), 1)) > 0) {
-                       nbytes += r;
-                       if (r < PIPE_BUF) break;
+                       while ((r = sread(fd, RCAST(void *, &buf[nbytes]),
+                           CAST(size_t, ms->bytes_max - nbytes), 1)) > 0) {
+                               nbytes += r;
+                               if (r < PIPE_BUF) break;
+                       }
                }
 
                if (nbytes == 0 && inname) {
@@ -488,13 +490,13 @@ file_or_fd(struct magic_set *ms, const char *inname, int fd)
                        goto done;
                }
 
-       } else {
+       } else if (fd != -1) {
                /* Windows refuses to read from a big console buffer. */
                size_t howmany =
 #if defined(WIN32)
-                               _isatty(fd) ? 8 * 1024 :
+                   _isatty(fd) ? 8 * 1024 :
 #endif
-                               ms->bytes_max;
+                   ms->bytes_max;
                if ((nbytes = read(fd, RCAST(void *, buf), howmany)) == -1) {
                        if (inname == NULL && fd != STDIN_FILENO)
                                file_error(ms, errno, "cannot read fd %d", fd);