exec: load_script: kill the onstack interp[BINPRM_BUF_SIZE] array

load_script() can simply use i_name instead, it points into bprm->buf[] and nobody can change this memory until we call prepare_binprm().

The only complication is that we need to also change the signature of bprm_change_interp() but this change looks good too.

While at it, do whitespace/style cleanups.

NOTE: the real motivation for this change is that people want to increase BINPRM_BUF_SIZE, we need to change load_misc_binary() too but this looks more complicated because afaics it is very buggy.

Signed-off-by Oleg Nesterov <[email protected]>

---
 fs/binfmt_script.c      | 17 +++++++++--------
 fs/exec.c               |  2 +-
 include/linux/binfmts.h |  2 +-
 3 files changed, 11 insertions(+), 10 deletions(-)

fs/binfmt_script.c +9 -8

index afdf4e3..7cde3f4 100644
@@ -19,7 +19,6 @@ static int load_script(struct linux_binprm *bprm)
        const char *i_arg, *i_name;
        char *cp;
        struct file *file;
-       char interp[BINPRM_BUF_SIZE];
        int retval;
 
        if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))

@@ -55,7 +54,7 @@ static int load_script(struct linux_binprm *bprm)
                        break;
        }
        for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
-       if (*cp == '\0')
+       if (*cp == '\0')
                return -ENOEXEC; /* No interpreter name found */
        i_name = cp;
        i_arg = NULL;

@@ -65,7 +64,6 @@ static int load_script(struct linux_binprm *bprm)
                *cp++ = '\0';
        if (*cp)
                i_arg = cp;
-       strcpy (interp, i_name);
        /*
         * OK, we've parsed out the interpreter name and
         * (optional) argument.

@@ -80,24 +78,27 @@ static int load_script(struct linux_binprm *bprm)
        if (retval)
                return retval;
        retval = copy_strings_kernel(1, &bprm->interp, bprm);
-       if (retval < 0) return retval;
+       if (retval < 0)
+               return retval;
        bprm->argc++;
        if (i_arg) {
                retval = copy_strings_kernel(1, &i_arg, bprm);
-               if (retval < 0) return retval;
+               if (retval < 0)
+                       return retval;
                bprm->argc++;
        }
        retval = copy_strings_kernel(1, &i_name, bprm);
-       if (retval) return retval;
+       if (retval)
+               return retval;
        bprm->argc++;
-       retval = bprm_change_interp(interp, bprm);
+       retval = bprm_change_interp(i_name, bprm);
        if (retval < 0)
                return retval;
 
        /*
         * OK, now restart the process with the interpreter's dentry.
         */
-       file = open_exec(interp);
+       file = open_exec(i_name);
        if (IS_ERR(file))
                return PTR_ERR(file);
 

fs/exec.c +1 -1

index 01a9fb9..8a665ec 100644
@@ -1429,7 +1429,7 @@ static void free_bprm(struct linux_binprm *bprm)
        kfree(bprm);
 }
 
-int bprm_change_interp(char *interp, struct linux_binprm *bprm)
+int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
 {
        /* If a binfmt changed the interp, free it first. */
        if (bprm->interp != bprm->filename)

include/linux/binfmts.h +1 -2

index fb44d61..18d05b5 100644
@@ -131,7 +131,7 @@ extern int setup_arg_pages(struct linux_binprm * bprm,
                           int executable_stack);
 extern int transfer_args_to_stack(struct linux_binprm *bprm,
                                  unsigned long *sp_location);
-extern int bprm_change_interp(char *interp, struct linux_binprm *bprm);
+extern int bprm_change_interp(const char *interp, struct linux_binprm *bprm);
 extern int copy_strings_kernel(int argc, const char *const *argv,
                               struct linux_binprm *bprm);
 extern int prepare_bprm_creds(struct linux_binprm *bprm);
--

2.5.0