File: local-stack-grows-up.diff

package info (click to toggle)
glibc 2.24-10
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 223,412 kB
  • sloc: ansic: 991,967; asm: 261,800; sh: 10,385; makefile: 9,710; cpp: 4,169; python: 3,971; perl: 2,254; awk: 1,753; pascal: 1,521; yacc: 291; sed: 80
file content (19 lines) | stat: -rw-r--r-- 710 bytes parent folder | download | duplicates (3) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
 
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -683,9 +692,13 @@
 			prot) != 0)
 	    goto mprot_error;
 #elif _STACK_GROWS_UP
-	  if (mprotect ((char *) pd - pd->guardsize,
-			pd->guardsize - guardsize, prot) != 0)
-	    goto mprot_error;
+	  char *new_guard = (char *) (((uintptr_t) pd - guardsize) & ~pagesize_m1);
+	  char *old_guard = (char *) (((uintptr_t) pd - pd->guardsize) & ~pagesize_m1);
+	  /* The guard size difference might be > 0, but once rounded
+	     to the nearest page the size difference might be zero.  */
+	  if (old_guard - new_guard > 0)
+	    if (mprotect (old_guard, new_guard - old_guard, prot) != 0)
+	      goto mprot_error;
 #endif
 
 	  pd->guardsize = guardsize;