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tar: handle the case when opened created tarball happens to have fd#0

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Reproducer:
    exec 0>&-
    exec 1>&-
    tar czf z.tar.gz FILE

function                                             old     new   delta
vfork_compressor                                     229     257     +28

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-08-04 18:15:19 +02:00
parent 45d68c3749
commit 037759bb4f
1 changed files with 18 additions and 6 deletions
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24
archival/tar.c
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@ -611,6 +611,7 @@ static void NOINLINE vfork_compressor(int tar_fd, const char *gzip)
if (xvfork() == 0) {
/* child */
int tfd;
/* NB: close _first_, then move fds! */
close(data.wr);
# if WAIT_FOR_CHILD
@ -619,8 +620,23 @@ static void NOINLINE vfork_compressor(int tar_fd, const char *gzip)
* parent waits for this close to happen */
fcntl(status.wr, F_SETFD, FD_CLOEXEC);
# endif
/* copy it: parent's tar_fd variable must not change */
tfd = tar_fd;
if (tfd == 0) {
/* Output tar fd may be zero.
* xmove_fd(data.rd, 0) would destroy it.
* Reproducer:
* exec 0>&-
* exec 1>&-
* tar czf Z.tar.gz FILE
* Swapping move_fd's order wouldn't work:
* data.rd is 1 and _it_ would be destroyed.
*/
xmove_fd(tfd, 3);
tfd = 3;
}
xmove_fd(data.rd, 0);
xmove_fd(tar_fd, 1);
xmove_fd(tfd, 1);
/* exec gzip/bzip2 program/applet */
BB_EXECLP(gzip, gzip, "-f", (char *)0);
vfork_exec_errno = errno;
@ -715,11 +731,7 @@ static NOINLINE int writeTarFile(
return errorFlag;
}
#else /* !FEATURE_TAR_CREATE */
# define writeTarFile(...) 0
#endif
#endif /* FEATURE_TAR_CREATE */
#if ENABLE_FEATURE_TAR_FROM
static llist_t *append_file_list_to_list(llist_t *list)