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aports/community/libvirt/libvirt-fork-exec-deadlock.patch
Leo 26ac94048b community/libvirt: move from main
2020-09-13 08:04:24 +00:00

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From c0c3240552c833c354c3cf2deb86f928df7e7e4f Mon Sep 17 00:00:00 2001
From: Natanael Copa <ncopa@alpinelinux.org>
Date: Wed, 12 Aug 2020 19:51:05 +0200
Subject: [PATCH 1/2] util: avoid free() when reset log after fork
Doing malloc/free after fork is techincally not allowed in POSIX and
deadlocks[1] with musl libc.
[1]: https://gitlab.com/libvirt/libvirt/-/issues/52
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
---
src/util/vircommand.c | 4 ++--
src/util/virlog.c | 44 +++++++++++++++++++++++++++++++++----------
src/util/virlog.h | 1 +
3 files changed, 37 insertions(+), 12 deletions(-)
diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 76f7eb9a3d..17e5bb00d3 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -304,7 +304,7 @@ virFork(void)
/* Make sure any hook logging is sent to stderr, since child
* process may close the logfile FDs */
logprio = virLogGetDefaultPriority();
- virLogReset();
+ virLogResetWithoutFree();
virLogSetDefaultPriority(logprio);
/* Clear out all signal handlers from parent so nothing
@@ -861,7 +861,7 @@ virExec(virCommandPtr cmd)
goto fork_error;
/* Close logging again to ensure no FDs leak to child */
- virLogReset();
+ virLogResetWithoutFree();
if (cmd->env)
execve(binary, cmd->args, cmd->env);
diff --git a/src/util/virlog.c b/src/util/virlog.c
index 3217e5eb73..3959de5ca7 100644
--- a/src/util/virlog.c
+++ b/src/util/virlog.c
@@ -108,8 +108,8 @@ static size_t virLogNbOutputs;
*/
static virLogPriority virLogDefaultPriority = VIR_LOG_DEFAULT;
-static void virLogResetFilters(void);
-static void virLogResetOutputs(void);
+static void virLogResetFilters(bool freemem);
+static void virLogResetOutputs(bool freemem);
static void virLogOutputToFd(virLogSourcePtr src,
virLogPriority priority,
const char *filename,
@@ -284,8 +284,30 @@ virLogReset(void)
return -1;
virLogLock();
- virLogResetFilters();
- virLogResetOutputs();
+ virLogResetFilters(true);
+ virLogResetOutputs(true);
+ virLogDefaultPriority = VIR_LOG_DEFAULT;
+ virLogUnlock();
+ return 0;
+}
+
+/**
+ * virLogResetWithoutFree:
+ *
+ * Reset the logging module to its default initial state, but avoid doing
+ * free() so it can be used after fork and before exec.
+ *
+ * Returns 0 if successful, and -1 in case or error
+ */
+int
+virLogResetWithoutFree(void)
+{
+ if (virLogInitialize() < 0)
+ return -1;
+
+ virLogLock();
+ virLogResetFilters(false);
+ virLogResetOutputs(false);
virLogDefaultPriority = VIR_LOG_DEFAULT;
virLogUnlock();
return 0;
@@ -324,9 +346,10 @@ virLogSetDefaultPriority(virLogPriority priority)
* Removes the set of logging filters defined.
*/
static void
-virLogResetFilters(void)
+virLogResetFilters(bool freemem)
{
- virLogFilterListFree(virLogFilters, virLogNbFilters);
+ if (freemem)
+ virLogFilterListFree(virLogFilters, virLogNbFilters);
virLogFilters = NULL;
virLogNbFilters = 0;
virLogFiltersSerial++;
@@ -371,9 +394,10 @@ virLogFilterListFree(virLogFilterPtr *list, int count)
* Removes the set of logging output defined.
*/
static void
-virLogResetOutputs(void)
+virLogResetOutputs(bool freemem)
{
- virLogOutputListFree(virLogOutputs, virLogNbOutputs);
+ if (freemem)
+ virLogOutputListFree(virLogOutputs, virLogNbOutputs);
virLogOutputs = NULL;
virLogNbOutputs = 0;
}
@@ -1392,7 +1416,7 @@ virLogDefineOutputs(virLogOutputPtr *outputs, size_t noutputs)
return -1;
virLogLock();
- virLogResetOutputs();
+ virLogResetOutputs(true);
#if HAVE_SYSLOG_H
/* syslog needs to be special-cased, since it keeps the fd in private */
@@ -1435,7 +1459,7 @@ virLogDefineFilters(virLogFilterPtr *filters, size_t nfilters)
return -1;
virLogLock();
- virLogResetFilters();
+ virLogResetFilters(true);
virLogFilters = filters;
virLogNbFilters = nfilters;
virLogUnlock();
diff --git a/src/util/virlog.h b/src/util/virlog.h
index 984a9d5a43..69f7b1ef94 100644
--- a/src/util/virlog.h
+++ b/src/util/virlog.h
@@ -168,6 +168,7 @@ void virLogSetDefaultOutput(const char *fname, bool godaemon, bool privileged);
void virLogLock(void);
void virLogUnlock(void);
int virLogReset(void);
+int virLogResetWithoutFree(void);
int virLogParseDefaultPriority(const char *priority);
int virLogPriorityFromSyslog(int priority);
void virLogMessage(virLogSourcePtr source,
--
2.28.0
From 9d070b977c7031263504e32a753facc6a28f5980 Mon Sep 17 00:00:00 2001
From: Natanael Copa <ncopa@alpinelinux.org>
Date: Wed, 19 Aug 2020 11:28:43 +0200
Subject: [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@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
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