linux/fs/binfmt_script.c
Oleg Nesterov c2315c187f exec: load_script: kill the onstack interp[BINPRM_BUF_SIZE] array
Patch series "exec: binfmt_misc: fix use-after-free, kill
iname[BINPRM_BUF_SIZE]".

It looks like this code was always wrong, then commit 948b701a60
("binfmt_misc: add persistent opened binary handler for containers")
added more problems.

This patch (of 6):

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.

Link: http://lkml.kernel.org/r/20170918163446.GA26793@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Travis Gummels <tgummels@redhat.com>
Cc: Ben Woodard <woodard@redhat.com>
Cc: Jim Foraker <foraker1@llnl.gov>
Cc: <tdhooge@llnl.gov>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-03 17:54:25 -07:00

131 lines
3.0 KiB
C

/*
* linux/fs/binfmt_script.c
*
* Copyright (C) 1996 Martin von Löwis
* original #!-checking implemented by tytso.
*/
#include <linux/module.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/binfmts.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/err.h>
#include <linux/fs.h>
static int load_script(struct linux_binprm *bprm)
{
const char *i_arg, *i_name;
char *cp;
struct file *file;
int retval;
if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!'))
return -ENOEXEC;
/*
* If the script filename will be inaccessible after exec, typically
* because it is a "/dev/fd/<fd>/.." path against an O_CLOEXEC fd, give
* up now (on the assumption that the interpreter will want to load
* this file).
*/
if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
return -ENOENT;
/*
* This section does the #! interpretation.
* Sorta complicated, but hopefully it will work. -TYT
*/
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
if ((cp = strchr(bprm->buf, '\n')) == NULL)
cp = bprm->buf+BINPRM_BUF_SIZE-1;
*cp = '\0';
while (cp > bprm->buf) {
cp--;
if ((*cp == ' ') || (*cp == '\t'))
*cp = '\0';
else
break;
}
for (cp = bprm->buf+2; (*cp == ' ') || (*cp == '\t'); cp++);
if (*cp == '\0')
return -ENOEXEC; /* No interpreter name found */
i_name = cp;
i_arg = NULL;
for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++)
/* nothing */ ;
while ((*cp == ' ') || (*cp == '\t'))
*cp++ = '\0';
if (*cp)
i_arg = cp;
/*
* OK, we've parsed out the interpreter name and
* (optional) argument.
* Splice in (1) the interpreter's name for argv[0]
* (2) (optional) argument to interpreter
* (3) filename of shell script (replace argv[0])
*
* This is done in reverse order, because of how the
* user environment and arguments are stored.
*/
retval = remove_arg_zero(bprm);
if (retval)
return retval;
retval = copy_strings_kernel(1, &bprm->interp, bprm);
if (retval < 0)
return retval;
bprm->argc++;
if (i_arg) {
retval = copy_strings_kernel(1, &i_arg, bprm);
if (retval < 0)
return retval;
bprm->argc++;
}
retval = copy_strings_kernel(1, &i_name, bprm);
if (retval)
return retval;
bprm->argc++;
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(i_name);
if (IS_ERR(file))
return PTR_ERR(file);
bprm->file = file;
retval = prepare_binprm(bprm);
if (retval < 0)
return retval;
return search_binary_handler(bprm);
}
static struct linux_binfmt script_format = {
.module = THIS_MODULE,
.load_binary = load_script,
};
static int __init init_script_binfmt(void)
{
register_binfmt(&script_format);
return 0;
}
static void __exit exit_script_binfmt(void)
{
unregister_binfmt(&script_format);
}
core_initcall(init_script_binfmt);
module_exit(exit_script_binfmt);
MODULE_LICENSE("GPL");