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Add helper functions to copy strings into struct image_args.

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Given a zeroed struct image_args with an allocated buf member,
exec_args_add_fname() must be called to install a file name (or NULL).
Then zero or more calls to exec_args_add_env() followed by zero or
more calls to exec_args_add_env(). exec_args_adjust_args() may be
called after args and/or env to allow an interpreter to be prepended to
the argument list.

To allow code reuse when adding arg and env variables, begin_envv
should be accessed with the accessor exec_args_get_begin_envv()
which handles the case when no environment entries have been added.

Use these functions to simplify exec_copyin_args() and
freebsd32_exec_copyin_args().

Reviewed by:	kib
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D15468
This commit is contained in:
brooks 2018-11-29 21:00:56 +00:00
parent 8d1fd0fff1
commit 54c8f3c8e7
7 changed files with 168 additions and 105 deletions
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5
sys/compat/cloudabi32/cloudabi32_module.c
View File

@ -54,7 +54,7 @@ cloudabi32_copyout_strings(struct image_params *imgp)
/* Copy out program arguments. */
args = imgp->args;
len = args->begin_envv - args->begin_argv;
len = exec_args_get_begin_envv(args) - args->begin_argv;
begin = rounddown2(imgp->sysent->sv_usrstack - len, sizeof(register_t));
copyout(args->begin_argv, (void *)begin, len);
return ((register_t *)begin);
@ -109,7 +109,8 @@ cloudabi32_fixup(register_t **stack_base, struct image_params *imgp)
* exec_copyin_data_fds(). Undo this by reducing the length.
*/
args = (Elf32_Auxargs *)imgp->auxargs;
argdatalen = imgp->args->begin_envv - imgp->args->begin_argv;
argdatalen = exec_args_get_begin_envv(imgp->args) -
imgp->args->begin_argv;
if (argdatalen > 0)
--argdatalen;

5
sys/compat/cloudabi64/cloudabi64_module.c
View File

@ -54,7 +54,7 @@ cloudabi64_copyout_strings(struct image_params *imgp)
/* Copy out program arguments. */
args = imgp->args;
len = args->begin_envv - args->begin_argv;
len = exec_args_get_begin_envv(args) - args->begin_argv;
begin = rounddown2(imgp->sysent->sv_usrstack - len, sizeof(register_t));
copyout(args->begin_argv, (void *)begin, len);
return ((register_t *)begin);
@ -109,7 +109,8 @@ cloudabi64_fixup(register_t **stack_base, struct image_params *imgp)
* exec_copyin_data_fds(). Undo this by reducing the length.
*/
args = (Elf64_Auxargs *)imgp->auxargs;
argdatalen = imgp->args->begin_envv - imgp->args->begin_argv;
argdatalen = exec_args_get_begin_envv(imgp->args) -
imgp->args->begin_argv;
if (argdatalen > 0)
--argdatalen;

40
sys/compat/freebsd32/freebsd32_misc.c
View File

@ -337,7 +337,6 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
{
char *argp, *envp;
u_int32_t *p32, arg;
size_t length;
int error;
bzero(args, sizeof(*args));
@ -355,19 +354,9 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
/*
* Copy the file name.
*/
if (fname != NULL) {
args->fname = args->buf;
error = (segflg == UIO_SYSSPACE) ?
copystr(fname, args->fname, PATH_MAX, &length) :
copyinstr(fname, args->fname, PATH_MAX, &length);
if (error != 0)
goto err_exit;
} else
length = 0;
args->begin_argv = args->buf + length;
args->endp = args->begin_argv;
args->stringspace = ARG_MAX;
error = exec_args_add_fname(args, fname, segflg);
if (error != 0)
goto err_exit;
/*
* extract arguments first
@ -380,19 +369,11 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
if (arg == 0)
break;
argp = PTRIN(arg);
error = copyinstr(argp, args->endp, args->stringspace, &length);
if (error) {
if (error == ENAMETOOLONG)
error = E2BIG;
error = exec_args_add_arg(args, argp, UIO_USERSPACE);
if (error != 0)
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->argc++;
}
args->begin_envv = args->endp;
/*
* extract environment strings
*/
@ -405,16 +386,9 @@ freebsd32_exec_copyin_args(struct image_args *args, const char *fname,
if (arg == 0)
break;
envp = PTRIN(arg);
error = copyinstr(envp, args->endp, args->stringspace,
&length);
if (error) {
if (error == ENAMETOOLONG)
error = E2BIG;
error = exec_args_add_env(args, envp, UIO_USERSPACE);
if (error != 0)
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->envc++;
}
}

15
sys/kern/imgact_binmisc.c
View File

@ -649,22 +649,13 @@ imgact_binmisc_exec(struct image_params *imgp)
s++;
}
/* Check to make sure we won't overrun the stringspace. */
if (offset > imgp->args->stringspace) {
/* Make room for the interpreter */
error = exec_args_adjust_args(imgp->args, 0, offset);
if (error != 0) {
sx_sunlock(&interp_list_sx);
error = E2BIG;
goto done;
}
/* Make room for the interpreter */
bcopy(imgp->args->begin_argv, imgp->args->begin_argv + offset,
imgp->args->endp - imgp->args->begin_argv);
/* Adjust everything by the offset. */
imgp->args->begin_envv += offset;
imgp->args->endp += offset;
imgp->args->stringspace -= offset;
/* Add the new argument(s) in the count. */
imgp->args->argc += ibe->ibe_interp_argcnt;

13
sys/kern/imgact_shell.c
View File

@ -196,20 +196,13 @@ exec_shell_imgact(struct image_params *imgp)
length = (imgp->args->argc == 0) ? 0 :
strlen(imgp->args->begin_argv) + 1; /* bytes to delete */
if (offset > imgp->args->stringspace + length) {
error = exec_args_adjust_args(imgp->args, length, offset);
if (error != 0) {
if (sname != NULL)
sbuf_delete(sname);
return (E2BIG);
return (error);
}
bcopy(imgp->args->begin_argv + length, imgp->args->begin_argv + offset,
imgp->args->endp - (imgp->args->begin_argv + length));
offset -= length; /* calculate actual adjustment */
imgp->args->begin_envv += offset;
imgp->args->endp += offset;
imgp->args->stringspace -= offset;
/*
* If there was no arg[0] when we started, then the interpreter_name
* is adding an argument (instead of replacing the arg[0] we started

183
sys/kern/kern_exec.c
View File

@ -345,9 +345,9 @@ kern_execve(struct thread *td, struct image_args *args, struct mac *mac_p)
{
AUDIT_ARG_ARGV(args->begin_argv, args->argc,
args->begin_envv - args->begin_argv);
AUDIT_ARG_ENVV(args->begin_envv, args->envc,
args->endp - args->begin_envv);
exec_args_get_begin_envv(args) - args->begin_argv);
AUDIT_ARG_ENVV(exec_args_get_begin_envv(args), args->envc,
args->endp - exec_args_get_begin_envv(args));
return (do_execve(td, args, mac_p));
}
@ -717,7 +717,7 @@ interpret:
/*
* Malloc things before we need locks.
*/
i = imgp->args->begin_envv - imgp->args->begin_argv;
i = exec_args_get_begin_envv(imgp->args) - imgp->args->begin_argv;
/* Cache arguments if they fit inside our allowance */
if (ps_arg_cache_limit >= i + sizeof(struct pargs)) {
newargs = pargs_alloc(i);
@ -1171,9 +1171,8 @@ int
exec_copyin_args(struct image_args *args, const char *fname,
enum uio_seg segflg, char **argv, char **envv)
{
u_long argp, envp;
u_long arg, env;
int error;
size_t length;
bzero(args, sizeof(*args));
if (argv == NULL)
@ -1190,67 +1189,43 @@ exec_copyin_args(struct image_args *args, const char *fname,
/*
* Copy the file name.
*/
if (fname != NULL) {
args->fname = args->buf;
error = (segflg == UIO_SYSSPACE) ?
copystr(fname, args->fname, PATH_MAX, &length) :
copyinstr(fname, args->fname, PATH_MAX, &length);
if (error != 0)
goto err_exit;
} else
length = 0;
args->begin_argv = args->buf + length;
args->endp = args->begin_argv;
args->stringspace = ARG_MAX;
error = exec_args_add_fname(args, fname, segflg);
if (error != 0)
goto err_exit;
/*
* extract arguments first
*/
for (;;) {
error = fueword(argv++, &argp);
error = fueword(argv++, &arg);
if (error == -1) {
error = EFAULT;
goto err_exit;
}
if (argp == 0)
if (arg == 0)
break;
error = copyinstr((void *)(uintptr_t)argp, args->endp,
args->stringspace, &length);
if (error != 0) {
if (error == ENAMETOOLONG)
error = E2BIG;
error = exec_args_add_arg(args, (char *)(uintptr_t)arg,
UIO_USERSPACE);
if (error != 0)
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->argc++;
}
args->begin_envv = args->endp;
/*
* extract environment strings
*/
if (envv) {
for (;;) {
error = fueword(envv++, &envp);
error = fueword(envv++, &env);
if (error == -1) {
error = EFAULT;
goto err_exit;
}
if (envp == 0)
if (env == 0)
break;
error = copyinstr((void *)(uintptr_t)envp,
args->endp, args->stringspace, &length);
if (error != 0) {
if (error == ENAMETOOLONG)
error = E2BIG;
error = exec_args_add_env(args,
(char *)(uintptr_t)env, UIO_USERSPACE);
if (error != 0)
goto err_exit;
}
args->stringspace -= length;
args->endp += length;
args->envc++;
}
}
@ -1305,8 +1280,6 @@ exec_copyin_data_fds(struct thread *td, struct image_args *args,
/* No argument buffer provided. */
args->endp = args->begin_argv;
}
/* There are no environment variables. */
args->begin_envv = args->endp;
/* Create new file descriptor table. */
kfds = malloc(fdslen * sizeof(int), M_TEMP, M_WAITOK);
@ -1462,6 +1435,126 @@ exec_free_args(struct image_args *args)
fdescfree_remapped(args->fdp);
}
/*
* A set to functions to fill struct image args.
*
* NOTE: exec_args_add_fname() must be called (possibly with a NULL
* fname) before the other functions. All exec_args_add_arg() calls must
* be made before any exec_args_add_env() calls. exec_args_adjust_args()
* may be called any time after exec_args_add_fname().
*
* exec_args_add_fname() - install path to be executed
* exec_args_add_arg() - append an argument string
* exec_args_add_env() - append an env string
* exec_args_adjust_args() - adjust location of the argument list to
* allow new arguments to be prepended
*/
int
exec_args_add_fname(struct image_args *args, const char *fname,
enum uio_seg segflg)
{
int error;
size_t length;
KASSERT(args->fname == NULL, ("fname already appended"));
KASSERT(args->endp == NULL, ("already appending to args"));
if (fname != NULL) {
args->fname = args->buf;
error = segflg == UIO_SYSSPACE ?
copystr(fname, args->fname, PATH_MAX, &length) :
copyinstr(fname, args->fname, PATH_MAX, &length);
if (error != 0)
return (error == ENAMETOOLONG ? E2BIG : error);
} else
length = 0;
/* Set up for _arg_*()/_env_*() */
args->endp = args->buf + length;
/* begin_argv must be set and kept updated */
args->begin_argv = args->endp;
KASSERT(exec_map_entry_size - length >= ARG_MAX,
("too little space remaining for arguments %zu < %zu",
exec_map_entry_size - length, (size_t)ARG_MAX));
args->stringspace = ARG_MAX;
return (0);
}
static int
exec_args_add_str(struct image_args *args, const char *str,
enum uio_seg segflg, int *countp)
{
int error;
size_t length;
KASSERT(args->endp != NULL, ("endp not initialized"));
KASSERT(args->begin_argv != NULL, ("begin_argp not initialized"));
error = (segflg == UIO_SYSSPACE) ?
copystr(str, args->endp, args->stringspace, &length) :
copyinstr(str, args->endp, args->stringspace, &length);
if (error != 0)
return (error == ENAMETOOLONG ? E2BIG : error);
args->stringspace -= length;
args->endp += length;
(*countp)++;
return (0);
}
int
exec_args_add_arg(struct image_args *args, const char *argp,
enum uio_seg segflg)
{
KASSERT(args->envc == 0, ("appending args after env"));
return (exec_args_add_str(args, argp, segflg, &args->argc));
}
int
exec_args_add_env(struct image_args *args, const char *envp,
enum uio_seg segflg)
{
if (args->envc == 0)
args->begin_envv = args->endp;
return (exec_args_add_str(args, envp, segflg, &args->envc));
}
int
exec_args_adjust_args(struct image_args *args, size_t consume, ssize_t extend)
{
ssize_t offset;
KASSERT(args->endp != NULL, ("endp not initialized"));
KASSERT(args->begin_argv != NULL, ("begin_argp not initialized"));
offset = extend - consume;
if (args->stringspace < offset)
return (E2BIG);
memmove(args->begin_argv + extend, args->begin_argv + consume,
args->endp - args->begin_argv + consume);
if (args->envc > 0)
args->begin_envv += offset;
args->endp += offset;
args->stringspace -= offset;
return (0);
}
char *
exec_args_get_begin_envv(struct image_args *args)
{
KASSERT(args->endp != NULL, ("endp not initialized"));
if (args->envc > 0)
return (args->begin_envv);
return (args->endp);
}
/*
* Copy strings out to the new process address space, constructing new arg
* and env vector tables. Return a pointer to the base so that it can be used

12
sys/sys/imgact.h
View File

@ -46,7 +46,8 @@ struct image_args {
char *buf; /* pointer to string buffer */
void *bufkva; /* cookie for string buffer KVA */
char *begin_argv; /* beginning of argv in buf */
char *begin_envv; /* beginning of envv in buf */
char *begin_envv; /* (interal use only) beginning of envv in buf,
* access with exec_args_get_begin_envv(). */
char *endp; /* current `end' pointer of arg & env strings */
char *fname; /* pointer to filename of executable (system space) */
char *fname_buf; /* pointer to optional malloc(M_TEMP) buffer */
@ -96,6 +97,15 @@ struct thread;
struct vmspace;
int exec_alloc_args(struct image_args *);
int exec_args_add_arg(struct image_args *args, const char *argp,
enum uio_seg segflg);
int exec_args_add_env(struct image_args *args, const char *envp,
enum uio_seg segflg);
int exec_args_add_fname(struct image_args *args, const char *fname,
enum uio_seg segflg);
int exec_args_adjust_args(struct image_args *args, size_t consume,
ssize_t extend);
char *exec_args_get_begin_envv(struct image_args *args);
int exec_check_permissions(struct image_params *);
register_t *exec_copyout_strings(struct image_params *);
void exec_free_args(struct image_args *);