Fix some #! misparsing in check_interpreter

* exec/exec.c: Do not include ctype.h, as the kernel
does not care about the locale.
(check_interpreter): Treat only spaces and tabs as white space.
Do not inspect more bytes than were read.
Although the resulting code does not exactly match what
the Android kernel does, it’s closer than what it was before.

(cherry picked from commit e0b027d1215ed32fe0f3d0956d2d7a81552274f2)

diff --git a/exec/exec.c b/exec/exec.c
index 775a8b06b968018b6d688c3e6670efdf243f731e..f31c9a8974414d56d4fb63058aa76a6d948648b1 100644 (file)
--- a/exec/exec.c
+++ b/exec/exec.c
@@ -24,7 +24,6 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include <fcntl.h>
 #include <assert.h>
 #include <string.h>
-#include <ctype.h>
 #include <stdlib.h>
 
 #include <sys/ptrace.h>
@@ -116,11 +115,11 @@ check_interpreter (const char *name, int fd, const char **extra)
 
   /* Strip leading whitespace.  */
   start = buffer;
-  while (*start && ((unsigned char) *start) < 128 && isspace (*start))
+  while (start < buffer + rc && (*start == ' ' || *start == '\t'))
     ++start;
 
   /* Look for a newline character.  */
-  end = memchr (start, '\n', rc);
+  end = memchr (start, '\n', buffer + rc - start);
 
   if (!end)
     goto fail;
@@ -130,11 +129,12 @@ check_interpreter (const char *name, int fd, const char **extra)
   *end = '\0';
 
   /* Now look for any whitespace characters.  */
-  ws = strchr (start, ' ');
+  for (ws = start; *ws && *ws != ' ' && *ws != '\t'; ws++)
+    continue;
 
   /* If there's no whitespace, return the entire start.  */
 
-  if (!ws)
+  if (!*ws)
     {
       if (lseek (fd, 0, SEEK_SET))
        goto fail;