Fix read_file in case file size if > SSIZE_MAX

src/read_file.c

@@ -1,10 +1,11 @@
-#include    <stdlib.h>
-#include    <fcntl.h>
-#include    <unistd.h>
-#include    <errno.h>
-#include    <sys/types.h>
-#include    <sys/stat.h>
-#include   "ucore/read_file.h"
+#include <stdlib.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include "ucore/read_file.h"
 
 #define CHUNK_SZ 1024
 
@@ -27,17 +28,21 @@ uc_read_file(const char *f, size_t *length, size_t max)
     }
 
     if ((statb.st_mode & S_IFMT) == S_IFREG) {
-        if ((size_t)statb.st_size > max) {
+        if (statb.st_size > (off_t)max) {
             errno = EMSGSIZE;
             goto out_close;
         }
-        alloc_sz = (size_t) statb.st_size + 1; // + 1 to avoid one realloc
-        s = malloc((size_t) alloc_sz + 1); //+1 for nul terminator
+        if (statb.st_size > SSIZE_MAX) {
+            //otherwise we cannot detect the return value of read()
+            alloc_sz = SSIZE_MAX;
+        } else {
+            alloc_sz = statb.st_size; 
+        }
     } else {
         alloc_sz = CHUNK_SZ;
-        s = malloc(alloc_sz + 1); //+1 for nul terminator
     }
 
+    s = malloc(alloc_sz + 1); //+1 for nul terminator
     if (s == NULL) {
         goto out_close;
     }