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hush: fix "redirects can close script fd" bug

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2016-08-22 19:54:12 +02:00
parent d8e61bbf13
commit aa3576a29b
4 changed files with 186 additions and 69 deletions
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24
include/libbb.h
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@ -185,24 +185,32 @@ int klogctl(int type, char *b, int len);
/* Busybox does not use threads, we can speed up stdio. */
#ifdef HAVE_UNLOCKED_STDIO
# undef getc
# define getc(stream) getc_unlocked(stream)
# define getc(stream) getc_unlocked(stream)
# undef getchar
# define getchar() getchar_unlocked()
# define getchar() getchar_unlocked()
# undef putc
# define putc(c, stream) putc_unlocked(c, stream)
# define putc(c,stream) putc_unlocked(c,stream)
# undef putchar
# define putchar(c) putchar_unlocked(c)
# define putchar(c) putchar_unlocked(c)
# undef fgetc
# define fgetc(stream) getc_unlocked(stream)
# define fgetc(stream) getc_unlocked(stream)
# undef fputc
# define fputc(c, stream) putc_unlocked(c, stream)
# define fputc(c,stream) putc_unlocked(c,stream)
#endif
/* Above functions are required by POSIX.1-2008, below ones are extensions */
#ifdef HAVE_UNLOCKED_LINE_OPS
# undef fgets
# define fgets(s, n, stream) fgets_unlocked(s, n, stream)
# define fgets(s,n,stream) fgets_unlocked(s,n,stream)
# undef fputs
# define fputs(s, stream) fputs_unlocked(s, stream)
# define fputs(s,stream) fputs_unlocked(s,stream)
# undef fflush
# define fflush(stream) fflush_unlocked(stream)
# undef feof
# define feof(stream) feof_unlocked(stream)
# undef ferror
# define ferror(stream) ferror_unlocked(stream)
# undef fileno
# define fileno(stream) fileno_unlocked(stream)
#endif

201
shell/hush.c
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@ -103,6 +103,9 @@
#else
# define CLEAR_RANDOM_T(rnd) ((void)0)
#endif
#ifndef F_DUPFD_CLOEXEC
# define F_DUPFD_CLOEXEC F_DUPFD
#endif
#ifndef PIPE_BUF
# define PIPE_BUF 4096 /* amount of buffering in a pipe */
#endif
@ -711,10 +714,10 @@ enum {
};
/* Can be extended to handle a FIXME in setup_redirects about not saving script fds */
struct FILE_list {
struct FILE_list *next;
FILE *fp;
int fd;
};
@ -809,9 +812,7 @@ struct globals {
unsigned handled_SIGCHLD;
smallint we_have_children;
#endif
#if ENABLE_FEATURE_SH_STANDALONE
struct FILE_list *FILE_list;
#endif
/* Which signals have non-DFL handler (even with no traps set)?
* Set at the start to:
* (SIGQUIT + maybe SPECIAL_INTERACTIVE_SIGS + maybe SPECIAL_JOBSTOP_SIGS)
@ -1262,35 +1263,34 @@ static void free_strings(char **strings)
}
static int xdup_and_close(int fd, int F_DUPFD_maybe_CLOEXEC)
{
/* We avoid taking stdio fds. Mimicking ash: use fds above 9 */
int newfd = fcntl(fd, F_DUPFD_maybe_CLOEXEC, 10);
if (newfd < 0) {
/* fd was not open? */
if (errno == EBADF)
return fd;
xfunc_die();
}
close(fd);
return newfd;
}
/* Manipulating the list of open FILEs */
static FILE *remember_FILE(FILE *fp)
{
if (fp) {
#if ENABLE_FEATURE_SH_STANDALONE
struct FILE_list *n = xmalloc(sizeof(*n));
n->fp = fp;
n->next = G.FILE_list;
G.FILE_list = n;
#endif
close_on_exec_on(fileno(fp));
n->fp = fp;
n->fd = fileno(fp);
close_on_exec_on(n->fd);
}
return fp;
}
#if ENABLE_FEATURE_SH_STANDALONE
static void close_all_FILE_list(void)
{
struct FILE_list *fl = G.FILE_list;
while (fl) {
/* fclose would also free FILE object.
* It is disastrous if we share memory with a vforked parent.
* I'm not sure we never come here after vfork.
* Therefore just close fd, nothing more.
*/
/*fclose(fl->fp); - unsafe */
close(fileno(fl->fp));
fl = fl->next;
}
}
static void fclose_and_forget(FILE *fp)
{
struct FILE_list **pp = &G.FILE_list;
@ -1305,8 +1305,46 @@ static void fclose_and_forget(FILE *fp)
}
fclose(fp);
}
#else
# define fclose_and_forget(fp) fclose(fp);
static int save_FILEs_on_redirect(int fd)
{
struct FILE_list *fl = G.FILE_list;
while (fl) {
if (fd == fl->fd) {
/* We use it only on script files, they are all CLOEXEC */
fl->fd = xdup_and_close(fd, F_DUPFD_CLOEXEC);
return 1;
}
fl = fl->next;
}
return 0;
}
static void restore_redirected_FILEs(void)
{
struct FILE_list *fl = G.FILE_list;
while (fl) {
int should_be = fileno(fl->fp);
if (fl->fd != should_be) {
xmove_fd(fl->fd, should_be);
fl->fd = should_be;
}
fl = fl->next;
}
}
#if ENABLE_FEATURE_SH_STANDALONE
static void close_all_FILE_list(void)
{
struct FILE_list *fl = G.FILE_list;
while (fl) {
/* fclose would also free FILE object.
* It is disastrous if we share memory with a vforked parent.
* I'm not sure we never come here after vfork.
* Therefore just close fd, nothing more.
*/
/*fclose(fl->fp); - unsafe */
close(fl->fd);
fl = fl->next;
}
}
#endif
@ -6147,6 +6185,74 @@ static void setup_heredoc(struct redir_struct *redir)
wait(NULL); /* wait till child has died */
}
/* fd: redirect wants this fd to be used (e.g. 3>file).
* Move all conflicting internally used fds,
* and remember them so that we can restore them later.
*/
static int save_fds_on_redirect(int fd, int squirrel[3])
{
if (squirrel) {
/* Handle redirects of fds 0,1,2 */
/* If we collide with an already moved stdio fd... */
if (fd == squirrel[0]) {
squirrel[0] = xdup_and_close(squirrel[0], F_DUPFD);
return 1;
}
if (fd == squirrel[1]) {
squirrel[1] = xdup_and_close(squirrel[1], F_DUPFD);
return 1;
}
if (fd == squirrel[2]) {
squirrel[2] = xdup_and_close(squirrel[2], F_DUPFD);
return 1;
}
/* If we are about to redirect stdio fd, and did not yet move it... */
if (fd <= 2 && squirrel[fd] < 0) {
/* We avoid taking stdio fds */
squirrel[fd] = fcntl(fd, F_DUPFD, 10);
if (squirrel[fd] < 0 && errno != EBADF)
xfunc_die();
return 0; /* "we did not close fd" */
}
}
#if ENABLE_HUSH_INTERACTIVE
if (fd != 0 && fd == G.interactive_fd) {
G.interactive_fd = xdup_and_close(G.interactive_fd, F_DUPFD_CLOEXEC);
return 1;
}
#endif
/* Are we called from setup_redirects(squirrel==NULL)? Two cases:
* (1) Redirect in a forked child. No need to save FILEs' fds,
* we aren't going to use them anymore, ok to trash.
* (2) "exec 3>FILE". Bummer. We can save FILEs' fds,
* but how are we doing to use them?
* "fileno(fd) = new_fd" can't be done.
*/
if (!squirrel)
return 0;
return save_FILEs_on_redirect(fd);
}
static void restore_redirects(int squirrel[3])
{
int i, fd;
for (i = 0; i <= 2; i++) {
fd = squirrel[i];
if (fd != -1) {
/* We simply die on error */
xmove_fd(fd, i);
}
}
/* Moved G.interactive_fd stays on new fd, not doing anything for it */
restore_redirected_FILEs();
}
/* squirrel != NULL means we squirrel away copies of stdin, stdout,
* and stderr if they are redirected. */
static int setup_redirects(struct command *prog, int squirrel[])
@ -6157,13 +6263,7 @@ static int setup_redirects(struct command *prog, int squirrel[])
for (redir = prog->redirects; redir; redir = redir->next) {
if (redir->rd_type == REDIRECT_HEREDOC2) {
/* "rd_fd<<HERE" case */
if (redir->rd_fd <= 2
&& squirrel
&& squirrel[redir->rd_fd] < 0
) {
/* Save old fds 0..2 if redirect uses them */
squirrel[redir->rd_fd] = dup(redir->rd_fd);
}
save_fds_on_redirect(redir->rd_fd, squirrel);
/* for REDIRECT_HEREDOC2, rd_filename holds _contents_
* of the heredoc */
debug_printf_parse("set heredoc '%s'\n",
@ -6199,47 +6299,26 @@ static int setup_redirects(struct command *prog, int squirrel[])
}
if (openfd != redir->rd_fd) {
if (redir->rd_fd <= 2
&& squirrel
&& squirrel[redir->rd_fd] < 0
) {
/* Save old fds 0..2 if redirect uses them */
//FIXME: script fd's also need this! "sh SCRIPT" and SCRIPT has "echo FOO 3>&-":
// open("SCRIPT", O_RDONLY) = 3
// fcntl(3, F_SETFD, FD_CLOEXEC) = 0
// read(3, "echo FOO 3>&-\n....", 4096) = N
// close(3) = 0
// write(1, "FOO\n", 4) = 4
// ...
// read(3, 0x205f8e0, 4096) = -1 EBADF <== BUG
//
squirrel[redir->rd_fd] = dup(redir->rd_fd);
}
int closed = save_fds_on_redirect(redir->rd_fd, squirrel);
if (openfd == REDIRFD_CLOSE) {
/* "n>-" means "close me" */
close(redir->rd_fd);
/* "rd_fd >&-" means "close me" */
if (!closed) {
/* ^^^ optimization: saving may already
* have closed it. If not... */
close(redir->rd_fd);
}
} else {
xdup2(openfd, redir->rd_fd);
if (redir->rd_dup == REDIRFD_TO_FILE)
/* "rd_fd > FILE" */
close(openfd);
/* else: "rd_fd > rd_dup" */
}
}
}
return 0;
}
static void restore_redirects(int squirrel[])
{
int i, fd;
for (i = 0; i <= 2; i++) {
fd = squirrel[i];
if (fd != -1) {
/* We simply die on error */
xmove_fd(fd, i);
}
}
}
static char *find_in_path(const char *arg)
{
char *ret = NULL;

1
shell/hush_test/hush-misc/redir_script.right Normal file
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@ -0,0 +1 @@
Ok: script fd is not closed

29
shell/hush_test/hush-misc/redir_script.tests Executable file
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@ -0,0 +1,29 @@
# Builds a " 3>&- 4>&-" string.
# Note: one of these fds is a directory opened to /proc/self/fd
# for globbing. It is unwanted, but I don't know how to filter it out.
find_fds() {
fds=""
for f in /proc/self/fd/*; do
test "$f" = "/proc/self/fd/0" && continue
test "$f" = "/proc/self/fd/1" && continue
test "$f" = "/proc/self/fd/2" && continue
fds="$fds ${f##*/}>&-"
done
}
find_fds
fds1="$fds"
# One of the fds is open to the script body
# Close it while executing something.
eval "find_fds $fds"
# Shell should not lose that fd. Did it?
find_fds
test x"$fds1" = x"$fds" && { echo "Ok: script fd is not closed"; exit 0; }
echo "Bug: script fd is closed"
echo "fds1:$fds1"
echo "fds2:$fds"
exit 1