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When relocating preserved fds, start with the highest ones first

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to avoid moving fds around more than we have to.  Now uses a bitmap
to keep track of which fds are being preserved.  Fixes a bug where
the debugging fd could be relocated to the same fd as the error
backchannel temporarily, resulting in debugging output being printed
to the backchannel if util@debug was enabled.
This commit is contained in:
Todd C. Miller
2014-01-14 20:20:26 -07:00
parent 26cff8bcb5
commit 77b126acc4
1 changed files with 46 additions and 48 deletions
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94
src/preserve_fds.c
View File

@@ -16,7 +16,13 @@
#include <config.h>
#include <sys/types.h>
#include <sys/param.h> /* for howmany() on Linux */
#ifdef HAVE_SYS_SYSMACROS_H
# include <sys/sysmacros.h> /* for howmany() on Solaris */
#endif /* HAVE_SYS_SYSMACROS_H */
#ifdef HAVE_SYS_SELECT_H
# include <sys/select.h> /* for FD_* macros */
#endif /* HAVE_SYS_SELECT_H */
#include <stdio.h>
#ifdef STDC_HEADERS
# include <stdlib.h>
@@ -65,6 +71,8 @@ add_preserved_fd(struct preserved_fd_list *pfds, int fd)
TAILQ_FOREACH(pfd, pfds, entries) {
if (fd == pfd->highfd) {
/* already preserved */
sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
"fd %d already preserved", fd);
efree(pfd_new);
break;
}
@@ -84,28 +92,6 @@ add_preserved_fd(struct preserved_fd_list *pfds, int fd)
debug_return_int(0);
}
/*
* Close fds in the range [from,to]
*/
static void
closefrom_range(int from, int to)
{
debug_decl(closefrom_range, SUDO_DEBUG_UTIL)
sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
"closing fds [%d, %d]", from, to);
while (from <= to) {
#ifdef __APPLE__
/* Avoid potential libdispatch crash when we close its fds. */
(void) fcntl(from, F_SETFD, FD_CLOEXEC);
#else
(void) close(from);
#endif
from++;
}
debug_return;
}
/*
* Close all descriptors, startfd and higher except those listed
* in pfds.
@@ -113,29 +99,31 @@ closefrom_range(int from, int to)
void
closefrom_except(int startfd, struct preserved_fd_list *pfds)
{
int tmpfd;
int fd, lastfd = -1;
struct preserved_fd *pfd, *pfd_next;
fd_set *fdsp;
debug_decl(closefrom_except, SUDO_DEBUG_UTIL)
/*
* First, relocate preserved fds to be as contiguous as possible.
*/
TAILQ_FOREACH_SAFE(pfd, pfds, entries, pfd_next) {
/* First, relocate preserved fds to be as contiguous as possible. */
TAILQ_FOREACH_REVERSE_SAFE(pfd, pfds, preserved_fd_list, entries, pfd_next) {
if (pfd->highfd < startfd)
continue;
tmpfd = dup(pfd->highfd);
if (tmpfd < pfd->highfd) {
if (tmpfd == -1) {
fd = dup(pfd->highfd);
if (fd < pfd->highfd) {
if (fd == -1) {
if (errno == EBADF)
TAILQ_REMOVE(pfds, pfd, entries);
continue;
}
pfd->lowfd = tmpfd;
tmpfd = pfd->highfd;
pfd->lowfd = fd;
fd = pfd->highfd;
sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
"dup %d -> %d", pfd->highfd, pfd->lowfd);
}
(void) close(tmpfd);
(void) close(fd);
if (pfd->lowfd > lastfd)
lastfd = pfd->lowfd; /* highest (relocated) preserved fd */
}
if (TAILQ_EMPTY(pfds)) {
@@ -146,24 +134,34 @@ closefrom_except(int startfd, struct preserved_fd_list *pfds)
debug_return;
}
/* Close any fds [startfd,TAILQ_FIRST(pfds)->lowfd) */
closefrom_range(startfd, TAILQ_FIRST(pfds)->lowfd - 1);
/* Close any unpreserved fds (TAILQ_LAST(pfds)->lowfd,startfd) */
TAILQ_FOREACH_SAFE(pfd, pfds, entries, pfd_next) {
if (pfd->lowfd < startfd)
continue;
if (pfd_next != NULL && pfd->lowfd + 1 != pfd_next->lowfd)
closefrom_range(pfd->lowfd + 1, pfd_next->lowfd);
/* Create bitmap of preserved (relocated) fds. */
fdsp = ecalloc(howmany(lastfd + 1, NFDBITS), sizeof(fd_mask));
TAILQ_FOREACH(pfd, pfds, entries) {
FD_SET(pfd->lowfd, fdsp);
}
/*
* Close any unpreserved fds [startfd,lastfd]
* NOTE: this could relocate the debug fd, breaking the debug subsystem.
*/
for (fd = startfd; fd <= lastfd; fd++) {
if (!FD_ISSET(fd, fdsp)) {
sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
"closing fd %d", fd);
#ifdef __APPLE__
/* Avoid potential libdispatch crash when we close its fds. */
(void) fcntl(fd, F_SETFD, FD_CLOEXEC);
#else
(void) close(fd);
#endif
}
}
free(fdsp);
/* Let closefrom() do the rest for us. */
pfd = TAILQ_LAST(pfds, preserved_fd_list);
if (pfd != NULL && pfd->lowfd + 1 > startfd)
startfd = pfd->lowfd + 1;
sudo_debug_printf(SUDO_DEBUG_DEBUG|SUDO_DEBUG_LINENO,
"closefrom(%d)", startfd);
closefrom(startfd);
"closefrom(%d)", lastfd + 1);
closefrom(lastfd + 1);
/* Restore preserved fds and set flags. */
TAILQ_FOREACH_REVERSE(pfd, pfds, preserved_fd_list, entries) {