c2315c187f
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>
130 lines
3 KiB
C
130 lines
3 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");
|