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ash,hush: ">&10" redirects to script/tty fds should not work

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The fact that shell has open fds to tty and/or scripts should be
unobservable, if possible. In particular, if redirect tries to dup
one of them via ">&script_fd", it's better to pretend that script_fd
is closed, and thus redirect fails with EBADF.

Fixes these two testcase failures:
ash-redir/redir_to_bad_fd.tests
hush-redir/redir_to_bad_fd3.tests

function                                             old     new   delta
redirect                                            1018    1129    +111
setup_redirects                                      250     359    +109
readtoken1                                          2651    2655      +4
cmdloop                                              185     187      +2
changepath                                           194     195      +1
save_fd_on_redirect                                  203     194      -9
evaltree                                             501     484     -17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/2 up/down: 227/-26)           Total: 201 bytes
   text    data     bss     dec     hex filename
 914553     485    6848  921886   e111e busybox_old
 914754     485    6848  922087   e11e7 busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-07-31 04:32:06 +02:00
parent 035486c750
commit 32fdf2f9fc
2 changed files with 72 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
shell/ash.c
View File

@ -5503,6 +5503,31 @@ save_fd_on_redirect(int fd, int avoid_fd, struct redirtab *sq)
return 0; /* "we did not close fd" */
}
static int
internally_opened_fd(int fd, struct redirtab *sq)
{
int i;
#if JOBS
if (fd == ttyfd)
return 1;
#endif
/* If this one of script's fds? */
if (fd != 0) {
struct parsefile *pf = g_parsefile;
while (pf) {
if (fd == pf->pf_fd)
return 1;
pf = pf->prev;
}
}
if (sq) for (i = 0; i < sq->pair_count && sq->two_fd[i].orig_fd != EMPTY; i++) {
if (fd == sq->two_fd[i].moved_to)
return 1;
}
return 0;
}
/*
* Process a list of redirection commands. If the REDIR_PUSH flag is set,
* old file descriptors are stashed away so that the redirection can be
@ -5567,15 +5592,11 @@ redirect(union node *redir, int flags)
close(fd);
}
} else {
///TODO: if _newfd_ is a script fd or saved fd, then simulate EBADF!
//if (newfd == ttyfd) {
// errno = EBADF;
// ash_msg_and_raise_perror("A %d", newfd);
//}
//if (newfd == g_parsefile->pf_fd) {
// errno = EBADF;
// ash_msg_and_raise_perror("B %d", newfd);
//}
/* if newfd is a script fd or saved fd, simulate EBADF */
if (internally_opened_fd(newfd, sv)) {
errno = EBADF;
ash_msg_and_raise_perror("%d", newfd);
}
dup2_or_raise(newfd, fd);
if (close_fd >= 0) /* "N>FILE" or ">&FILE" or heredoc? */
close(close_fd);

52
shell/hush.c
View File

@ -1546,6 +1546,16 @@ static void close_all_FILE_list(void)
}
}
#endif
static int fd_in_FILEs(int fd)
{
struct FILE_list *fl = G.FILE_list;
while (fl) {
if (fl->fd == fd)
return 1;
fl = fl->next;
}
return 0;
}
/* Helpers for setting new $n and restoring them back
@ -6686,9 +6696,9 @@ static struct squirrel *append_squirrel(struct squirrel *sq, int i, int orig, in
static struct squirrel *add_squirrel(struct squirrel *sq, int fd, int avoid_fd)
{
int moved_to;
int i = 0;
int i;
if (sq) while (sq[i].orig_fd >= 0) {
if (sq) for (i = 0; sq[i].orig_fd >= 0; i++) {
/* If we collide with an already moved fd... */
if (fd == sq[i].moved_to) {
sq[i].moved_to = fcntl_F_DUPFD(sq[i].moved_to, avoid_fd);
@ -6702,7 +6712,6 @@ static struct squirrel *add_squirrel(struct squirrel *sq, int fd, int avoid_fd)
debug_printf_redir("redirect_fd %d: already moved\n", fd);
return sq;
}
i++;
}
/* If this fd is open, we move and remember it; if it's closed, moved_to = -1 */
@ -6717,8 +6726,7 @@ static struct squirrel *add_squirrel_closed(struct squirrel *sq, int fd)
{
int i;
i = 0;
if (sq) while (sq[i].orig_fd >= 0) {
if (sq) for (i = 0; sq[i].orig_fd >= 0; i++) {
/* If we collide with an already moved fd... */
if (fd == sq[i].orig_fd) {
/* Examples:
@ -6730,7 +6738,6 @@ static struct squirrel *add_squirrel_closed(struct squirrel *sq, int fd)
debug_printf_redir("redirect_fd %d: already moved or closed\n", fd);
return sq;
}
i++;
}
debug_printf_redir("redirect_fd %d: previous fd was closed\n", fd);
@ -6747,7 +6754,8 @@ static int save_fd_on_redirect(int fd, int avoid_fd, struct squirrel **sqp)
avoid_fd = 9;
#if ENABLE_HUSH_INTERACTIVE
if (fd != 0 && fd == G.interactive_fd) {
if (fd == G.interactive_fd) {
/* Testcase: "ls -l /proc/$$/fd 255>&-" should work */
G.interactive_fd = xdup_CLOEXEC_and_close(G.interactive_fd, avoid_fd);
debug_printf_redir("redirect_fd %d: matches interactive_fd, moving it to %d\n", fd, G.interactive_fd);
return 1; /* "we closed fd" */
@ -6775,8 +6783,8 @@ static int save_fd_on_redirect(int fd, int avoid_fd, struct squirrel **sqp)
static void restore_redirects(struct squirrel *sq)
{
if (sq) {
int i = 0;
while (sq[i].orig_fd >= 0) {
int i;
for (i = 0; sq[i].orig_fd >= 0; i++) {
if (sq[i].moved_to >= 0) {
/* We simply die on error */
debug_printf_redir("restoring redirected fd from %d to %d\n", sq[i].moved_to, sq[i].orig_fd);
@ -6786,7 +6794,6 @@ static void restore_redirects(struct squirrel *sq)
debug_printf_redir("restoring redirected fd %d: closing it\n", sq[i].orig_fd);
close(sq[i].orig_fd);
}
i++;
}
free(sq);
}
@ -6796,6 +6803,25 @@ static void restore_redirects(struct squirrel *sq)
restore_redirected_FILEs();
}
static int internally_opened_fd(int fd, struct squirrel *sq)
{
int i;
#if ENABLE_HUSH_INTERACTIVE
if (fd == G.interactive_fd)
return 1;
#endif
/* If this one of script's fds? */
if (fd_in_FILEs(fd))
return 1;
if (sq) for (i = 0; sq[i].orig_fd >= 0; i++) {
if (fd == sq[i].moved_to)
return 1;
}
return 0;
}
/* squirrel != NULL means we squirrel away copies of stdin, stdout,
* and stderr if they are redirected. */
static int setup_redirects(struct command *prog, struct squirrel **sqp)
@ -6878,6 +6904,12 @@ static int setup_redirects(struct command *prog, struct squirrel **sqp)
* and second redirect closes 3! Restore code then closes 3 again.
*/
} else {
/* if newfd is a script fd or saved fd, simulate EBADF */
if (internally_opened_fd(newfd, sqp ? *sqp : NULL)) {
//errno = EBADF;
//bb_perror_msg_and_die("can't duplicate file descriptor");
newfd = -1; /* same effect as code above */
}
xdup2(newfd, redir->rd_fd);
if (redir->rd_dup == REDIRFD_TO_FILE)
/* "rd_fd > FILE" */