[LLVMbugs] [Bug 11843] New: Stack protection not working properly

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Jan 24 03:00:13 PST 2012


             Bug #: 11843
           Summary: Stack protection not working properly
           Product: dragonegg
           Version: 3.0
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: New Bugs
        AssignedTo: baldrick at free.fr
        ReportedBy: pbarrio at die.upm.es
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 7939
  --> http://llvm.org/bugs/attachment.cgi?id=7939
Resulting bitcode from dragonegg

Generated IR segfaults when executing with lli. Native executable works fine.
If option "-fno-stack-protector" is passed to dragonegg, it also works.

$> gcc -fplugin=~/dragonegg.so -O1 -fplugin-arg-dragonegg-enable-gcc-optzns
test.c -S -fplugin-arg-dragonegg-emit-ir -o test.ll

$> lli test.ll

The original code is:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char** argv){

        char a[15] = "aaaaaaaaaaaaaa";
        char b[15] = "bbbbbbbbbbbbbb";

        char *c = (char*) malloc(sizeof(char)*(strlen(a)+strlen(b)+1));
        memcpy(c, a, strlen(a));
        memcpy(c + strlen(a), b, strlen(b) + 1);

        printf("a = %s, b = %s, c = %s\n", a, b, c);

If arrays "a" and "b" are shrinked to 7 chars, then it works as well. If these
arrays are allocated with malloc or declared as globals (out of main), it also
works. It's very likely to be a stack issue.

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