Unfortunately, advisory record locking lose the lock if any fd refering
to the file is closed. There doesn't seem to be a way to preserve the
lock atomically. We could eventually retake the lock if low pidfilefd
is required.
This fixes processes being leaked, as they are not killed in
virPidFileForceCleanupPath() if the lock can be taken. Here also, we may
consider this is not good enough, as a process may leak by simply
closing the pidfilefd.
Fixes commit d146105f1e ("virCommand:
Actually acquire pidfile instead of just writing it")
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Our virCommand module allows us to set a pidfile for commands we
want to spawn. The caller constructs the string of pidfile path
and then uses virCommandSetPidFile() to tell the module to write
the pidfile once the command is ran. This usually works, but has
two flaws:
1) the child process does not hold the pidfile open & locked.
Therefore, the caller (or anybody else) can't use our fancy
virPidFileForceCleanupPath() function to kill the command
afterwards. Also, for everybody else on the system it's
needlessly harder to check if the pid from the pidfile is still
alive or not.
2) if the caller ever makes a mistake and passes the same pidfile
path for two different commands, the start of the second command
will overwrite the pidfile even though the first command might
still be running.
NOTE that this temporarily renders some command spawning
unusable, specifically those code patterns where both
virCommandSetPidFile() is used together with instructing spawned
command to acquire pidfile itself. Fortunately, there is only one
occurrence of such pattern and it is in
qemuProcessStartManagedPRDaemon(). This is fixed in next commit.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
This effectively reverts
commit 39c77fe586
Author: Michal Prívozník <mprivozn@redhat.com>
Date: Wed Jan 16 11:58:00 2013 +0100
Introduce event loop to commandtest
because nothing in the current test suite needs this
event loop.
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The recently added test27 spawns commandhelper. This is fine,
except, one of the things that commandhelper does is it records
arguments it was spawn with into commandhelper.log. Other test
cases then use checkoutput() to compare the arguments against the
expected ones and also unlink() the log file. However, test27()
is not doing that and thus it leaves the file behind. This
breaks distcheck.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
The only use of this code was removed by:
commit be78814ae0
Author: Michal Privoznik <mprivozn@redhat.com>
Date: Thu Apr 2 14:41:17 2015 +0200
virNetSocketNewConnectUNIX: Use flocks when spawning a daemon
less than a year after it was first introduced in
commit 1b807f92db
Author: Martin Kletzander <mkletzan@redhat.com>
Date: Wed Jul 16 08:00:19 2014 +0200
rpc: pass listen FD to the daemon being started
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
The QEMU command line arguments are very long and currently all written
on a single line to /var/log/libvirt/qemu/$GUEST.log. This introduces
logic to add line breaks after every env variable and "-" optional
argument, and every positional argument. This will create a clearer log
file, which will in turn present better in bug reports when people cut +
paste from the log into a bug comment.
An example log file entry now looks like this:
2018-12-14 12:57:03.677+0000: starting up libvirt version: 5.0.0, qemu version: 3.0.0qemu-3.0.0-1.fc29, kernel: 4.19.5-300.fc29.x86_64, hostname: localhost.localdomain
LC_ALL=C \
PATH=/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin \
HOME=/home/berrange \
USER=berrange \
LOGNAME=berrange \
QEMU_AUDIO_DRV=none \
/usr/bin/qemu-system-ppc64 \
-name guest=guest,debug-threads=on \
-S \
-object secret,id=masterKey0,format=raw,file=/home/berrange/.config/libvirt/qemu/lib/domain-33-guest/master-key.aes \
-machine pseries-2.10,accel=tcg,usb=off,dump-guest-core=off \
-m 1024 \
-realtime mlock=off \
-smp 1,sockets=1,cores=1,threads=1 \
-uuid c8a74977-ab18-41d0-ae3b-4041c7fffbcd \
-display none \
-no-user-config \
-nodefaults \
-chardev socket,id=charmonitor,fd=23,server,nowait \
-mon chardev=charmonitor,id=monitor,mode=control \
-rtc base=utc \
-no-shutdown \
-boot strict=on \
-device qemu-xhci,id=usb,bus=pci.0,addr=0x1 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
2018-12-14 12:57:03.730+0000: shutting down, reason=failed
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
That sets a new flag, but that flag does mean the child will get
LISTEN_FDS and LISTEN_PID environment variables properly set and
passed FDs reordered so that it corresponds with LISTEN_FDS (they must
start right after STDERR_FILENO).
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Commit 39c77fe triggered random failures, depending on the platform
and what other fds leak into the testsuite (for me, it passed on
RHEL 6 but failed on Fedora 18). The reason was that we were
expecting an fd that fell outside of our reserved range. By reserving
a larger range, the test once again passes on all platforms.
* tests/commandtest.c (mymain): Reserve enough fds.
Without this patch, logged command executions can be ambiguous if
the command contained any shell metacharacters. This has caused
more than one person to attempt to patch clients to add unnecessary
quoting, without realizing that the command itself was run with
correct args, and only the logged output was ambiguous.
* src/util/command.c (virCommandToString): Add shell escapes.
* tests/commandtest.c (test16): Test new behavior.
* tests/commanddata/test16.log: Update expected output.
* tests/qemuxml2argvdata/qemuxml2argv-*.args: Likewise.
* tests/networkxml2argvdata/*.argv: Likewise.
It is possible to deadlock libvirt by having a domain with XML
longer than PIPE_BUF, and by writing a hook script that closes
stdin early. This is because libvirt was keeping a copy of the
child's stdin read fd open, which means the write fd in the
parent will never see EPIPE (remember, libvirt should always be
run with SIGPIPE ignored, so we should never get a SIGPIPE signal).
Since there is no error, libvirt blocks waiting for a write to
complete, even though the only reader is also libvirt. The
solution is to ensure that only the child can act as a reader
before the parent does any writes; and then dealing with the
fallout of dealing with EPIPE.
Thankfully, this is not a security hole - since the only way to
trigger the deadlock is to install a custom hook script, anyone
that already has privileges to install a hook script already has
privileges to do any number of other equally disruptive things
to libvirt; it would only be a security hole if an unprivileged
user could install a hook script to DoS a privileged user.
* src/util/command.c (virCommandRun): Close parent's copy of child
read fd earlier.
(virCommandProcessIO): Don't let EPIPE be fatal; the child may
be done parsing input.
* tests/commandhelper.c (main): Set up a SIGPIPE situation.
* tests/commandtest.c (test20): Trigger it.
* tests/commanddata/test20.log: New file.
virBufferContentAndReset (intentionally) returns NULL for a buffer
with no content, but it is feasible to invoke a command with an
explicit empty string.
* src/util/command.c (virCommandAddEnvBuffer): Reject empty string.
(virCommandAddArgBuffer): Allow explicit empty argument.
* tests/commandtest.c (test9): Test it.
* tests/commanddata/test9.log: Adjust.
This introduces a new set of APIs in src/util/command.h
to use for invoking commands. This is intended to replace
all current usage of virRun and virExec variants, with a
more flexible and less error prone API.
* src/util/command.c: New file.
* src/util/command.h: New header.
* src/Makefile.am (UTIL_SOURCES): Build it.
* src/libvirt_private.syms: Export symbols internally.
* tests/commandtest.c: New test.
* tests/Makefile.am (check_PROGRAMS): Run it.
* tests/commandhelper.c: Auxiliary program.
* tests/commanddata/test2.log - test15.log: New expected outputs.
* cfg.mk (useless_free_options): Add virCommandFree.
(msg_gen_function): Add virCommandError.
* po/POTFILES.in: New translation.
* .x-sc_avoid_write: Add exemption.
* tests/.gitignore: Ignore new built file.
