Root priviledges can be restored after setuid(1000) in musl libc

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musl libc allows you to change uid to root even after supposedly dropping permissions with setuid(1000). I am not able to reproduce the problem with glibc.



Code:



#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>

int main(void) 
 uid_t r, e, s;

 getresuid(&r, &e, &s);
 printf("%d %d %dn", r, e, s);

 if (setuid(1000) != 0)
 puts("setuid(1000) failed");
 else
 puts("setuid(1000) succeded");

 getresuid(&r, &e, &s);
 printf("%d %d %dn", r, e, s);

 if (setuid(0) != 0)
 puts("setuid(0) failed");
 else
 puts("setuid(0) succeded");

 getresuid(&r, &e, &s);
 printf("%d %d %dn", r, e, s);

 return 0;



which after compiling with gcc -o setuidtest setuidtest.c produces the following output when running as root



0 0 0
setuid(1000) succeded
1000 1000 1000
setuid(0) succeded
0 0 0


I am running Void Linux with kernel version 4.18_1 and musl version 1.1.20_2






linux security setuid







share|improve this question

























    up vote
    0
    down vote

    favorite












    musl libc allows you to change uid to root even after supposedly dropping permissions with setuid(1000). I am not able to reproduce the problem with glibc.



    Code:



    #define _GNU_SOURCE
    #include <unistd.h>
    #include <stdio.h>

    int main(void) 
     uid_t r, e, s;

     getresuid(&r, &e, &s);
     printf("%d %d %dn", r, e, s);

     if (setuid(1000) != 0)
     puts("setuid(1000) failed");
     else
     puts("setuid(1000) succeded");

     getresuid(&r, &e, &s);
     printf("%d %d %dn", r, e, s);

     if (setuid(0) != 0)
     puts("setuid(0) failed");
     else
     puts("setuid(0) succeded");

     getresuid(&r, &e, &s);
     printf("%d %d %dn", r, e, s);

     return 0;



    which after compiling with gcc -o setuidtest setuidtest.c produces the following output when running as root



    0 0 0
    setuid(1000) succeded
    1000 1000 1000
    setuid(0) succeded
    0 0 0


    I am running Void Linux with kernel version 4.18_1 and musl version 1.1.20_2






    linux security setuid







    share|improve this question























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      musl libc allows you to change uid to root even after supposedly dropping permissions with setuid(1000). I am not able to reproduce the problem with glibc.



      Code:



      #define _GNU_SOURCE
      #include <unistd.h>
      #include <stdio.h>

      int main(void) 
       uid_t r, e, s;

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       if (setuid(1000) != 0)
       puts("setuid(1000) failed");
       else
       puts("setuid(1000) succeded");

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       if (setuid(0) != 0)
       puts("setuid(0) failed");
       else
       puts("setuid(0) succeded");

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       return 0;



      which after compiling with gcc -o setuidtest setuidtest.c produces the following output when running as root



      0 0 0
      setuid(1000) succeded
      1000 1000 1000
      setuid(0) succeded
      0 0 0


      I am running Void Linux with kernel version 4.18_1 and musl version 1.1.20_2






      linux security setuid







      share|improve this question













      musl libc allows you to change uid to root even after supposedly dropping permissions with setuid(1000). I am not able to reproduce the problem with glibc.



      Code:



      #define _GNU_SOURCE
      #include <unistd.h>
      #include <stdio.h>

      int main(void) 
       uid_t r, e, s;

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       if (setuid(1000) != 0)
       puts("setuid(1000) failed");
       else
       puts("setuid(1000) succeded");

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       if (setuid(0) != 0)
       puts("setuid(0) failed");
       else
       puts("setuid(0) succeded");

       getresuid(&r, &e, &s);
       printf("%d %d %dn", r, e, s);

       return 0;



      which after compiling with gcc -o setuidtest setuidtest.c produces the following output when running as root



      0 0 0
      setuid(1000) succeded
      1000 1000 1000
      setuid(0) succeded
      0 0 0


      I am running Void Linux with kernel version 4.18_1 and musl version 1.1.20_2






      linux security setuid




      linux security setuid






      share|improve this question













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