[PATCH 2/2] util: command: improve generic mass close of fds
Add a portable generic implementation of virMassClose as fallback on
non-FreeBSD and non-glibc.
This implementation uses poll(2) to look for open files to keep
performance reasonable while not using any mallocs.
This solves a deadlock with musl libc.
Signed-off-by: Natanael Copa <ncopa(a)alpinelinux.org>
---
src/util/vircommand.c | 76 +++++++++++++++++++++++++++++++++----------
1 file changed, 58 insertions(+), 18 deletions(-)
diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 17e5bb00d3..06579cfb44 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -443,7 +443,7 @@ virExecCommon(virCommandPtr cmd, gid_t *groups, int ngroups)
return 0;
}
-# ifdef __linux__
+# if defined(__linux__) && defined(__GLIBC__)
/* On Linux, we can utilize procfs and read the table of opened
* FDs and selectively close only those FDs we don't want to pass
* onto child process (well, the one we will exec soon since this
@@ -482,17 +482,7 @@ virCommandMassCloseGetFDsLinux(virCommandPtr cmd G_GNUC_UNUSED,
VIR_DIR_CLOSE(dp);
return ret;
}
-
-# else /* !__linux__ */
-
-static int
-virCommandMassCloseGetFDsGeneric(virCommandPtr cmd G_GNUC_UNUSED,
- virBitmapPtr fds)
-{
- virBitmapSetAll(fds);
- return 0;
-}
-# endif /* !__linux__ */
+# endif /* __linux__ && __GLIBC__ */
# ifdef __FreeBSD__
@@ -546,7 +536,7 @@ virCommandMassClose(virCommandPtr cmd,
return 0;
}
-# else /* ! __FreeBSD__ */
+# elif defined(__GLIBC_) /* ! __FreeBSD__ */
static int
virCommandMassClose(virCommandPtr cmd,
@@ -574,13 +564,8 @@ virCommandMassClose(virCommandPtr cmd,
if (!(fds = virBitmapNew(openmax)))
return -1;
-# ifdef __linux__
if (virCommandMassCloseGetFDsLinux(cmd, fds) < 0)
return -1;
-# else
- if (virCommandMassCloseGetFDsGeneric(cmd, fds) < 0)
- return -1;
-# endif
fd = virBitmapNextSetBit(fds, 2);
for (; fd >= 0; fd = virBitmapNextSetBit(fds, fd)) {
@@ -598,6 +583,61 @@ virCommandMassClose(virCommandPtr cmd,
return 0;
}
+#else /* ! __FreeBSD__ && ! __GLIBC__ */
+static int
+virCommandMassClose(virCommandPtr cmd,
+ int childin,
+ int childout,
+ int childerr)
+{
+ static struct pollfd pfds[1024];
+ int fd = 0;
+ int i, total;
+ int max_fd = sysconf(_SC_OPEN_MAX);
+
+ if (max_fd < 0) {
+ virReportSystemError(errno, "%s", _("sysconf(_SC_OPEN_MAX)
failed"));
+ return -1;
+ }
+
+ total = max_fd - fd;
+ for (i = 0; i < (total < 1024 ? total : 1024); i++)
+ pfds[i].events = 0;
+
+ while (fd < max_fd) {
+ int nfds, r = 0;
+
+ total = max_fd - fd;
+ nfds = total < 1024 ? total : 1024;
+
+ for (i = 0; i < nfds; i++)
+ pfds[i].fd = fd + i;
+
+ do {
+ r = poll(pfds, nfds, 0);
+ } while (r == -1 && errno == EINTR);
+
+ if (r < 0) {
+ virReportSystemError(errno, "%s", _("poll() failed"));
+ return -1;
+ }
+
+ for (i = 0; i < nfds; i++)
+ if (pfds[i].revents != POLLNVAL) {
+ if (pfds[i].fd == childin || pfds[i].fd == childout || pfds[i].fd ==
childerr)
+ continue;
+ if (!virCommandFDIsSet(cmd, pfds[i].fd)) {
+ VIR_MASS_CLOSE(pfds[i].fd);
+ } else if (virSetInherit(pfds[i].fd, true) < 0) {
+ virReportSystemError(errno, _("failed to preserve fd %d"),
pfds[i].fd);
+ return -1;
+ }
+ }
+ fd += nfds;
+ }
+ return 0;
+}
+
# endif /* ! __FreeBSD__ */
/*
--
2.28.0