Since libvirt is multi-threaded, we should use FD_CLOEXEC as much
as possible in the parent, and only relax fds to inherited after
forking, to avoid leaking an fd created in one thread to a fork
run in another thread. This gets us closer to that ideal, by
making virCommand automatically clear FD_CLOEXEC on fds intended
for the child, as well as avoiding a window of time with non-cloexec
pipes created for capturing output.
* src/util/command.c (virExecWithHook): Use CLOEXEC in parent. In
child, guarantee that all fds to pass to child are inheritable.
(getDevNull): Use CLOEXEC.
(prepareStdFd): New helper function.
(virCommandRun, virCommandRequireHandshake): Use pipe2.
* src/qemu/qemu_command.c (qemuBuildCommandLine): Simplify caller.
We already have a precedent of function documentation in C files,
where it is closer to the implementation (witness libvirt.h vs.
libvirt.c); maintaining docs in both files risks docs going stale.
While I was at it, I used consistent doxygen style on all comments.
* src/util/command.h: Remove duplicate docs, and move unique
documentation...
* src/util/command.c: ...here.
Suggested by Matthias Bolte.
Enforce the recent flags cleanups - we want to use 'unsigned int flags'
in any of our APIs (except where backwards compatibility is important,
in the public migration APIs), and that all flags are checked for
validity (except when there are stub functions that completely
ignore the flags argument).
There are a few minor tweaks done here to avoid false positives:
signed arguments passed to open() are renamed oflags, and flags
arguments that are legitimately ignored are renamed flags_unused.
* cfg.mk (sc_flags_usage): New rule.
(exclude_file_name_regexp--sc_flags_usage): And a few exemptions.
(sc_flags_debug): Tweak wording.
* src/util/iohelper.c (runIO, main): Rename variable.
* src/util/util.c (virSetInherit): Likewise.
* src/fdstream.h (virFDStreamOpenFile, virFDStreamCreateFile):
Likewise.
* src/fdstream.c (virFDStreamOpenFileInternal)
(virFDStreamOpenFile, virFDStreamCreateFile): Likewise.
* src/util/command.c (virExecWithHook) [WIN32]: Likewise.
* src/util/util.c (virFileOpenAs, virDirCreate) [WIN32]: Likewise.
* src/locking/lock_manager.c (virLockManagerPluginNew)
[!HAVE_DLFCN_H]: Likewise.
* src/locking/lock_driver_nop.c (virLockManagerNopNew)
(virLockManagerNopAddResource, virLockManagerNopAcquire)
(virLockManagerNopRelease, virLockManagerNopInquire): Likewise.
When using virCommandRunAsync and saving the pid for later, it
is useful to be able to reap that pid in the same way that it
would have been auto-reaped by virCommand if we had passed
NULL for the pid argument in the first place.
* src/util/command.c (virPidWait, virPidAbort): New functions,
created from...
(virCommandWait, virCommandAbort): ...bodies of these.
(includes): Drop duplicate <stdlib.h>. Ensure that our pid_t
assumptions hold.
(virCommandRunAsync): Improve documentation.
* src/util/command.h (virPidWait, virPidAbort): New prototypes.
* src/libvirt_private.syms: Export them.
* docs/internals/command.html.in: Document them.
Previously, the parent process opened 'null' to /dev/null, then
the child process closes 'null' as well as 'childout'. But if
childout was set to be null, then this is a double close. At
least the double close was confined to the child process after a
fork, and therefore there is no risk of another thread opening
an fd of the same value to be bitten by the double close, but it
is always better to avoid double-close to begin with.
Additionally, if all three fds were specified, then opening
'null' was wasted.
This patch fixes things to lazily open null on the first use,
then guarantees it gets closed exactly once.
* src/util/command.c (getDevNull): New helper function.
(virExecWithHook): Use it to avoid spurious opens and double close.
This also reduces malloc pressure for invoking a child when
VIR_DEBUG is enabled.
* src/util/command.c (virExecWithHook): Drop debug, since the only
caller (virCommandRunAsync) also prints debug info.
Similar in nature to commit fd21ecfd, which shut up valgrind.
sigaction is apparently a nasty interface for analyzer tools,
at least for how many false positives it generates.
* src/util/command.c (virExecWithHook): Initialize entire var, since
coverity gripes about the (unused and non-standard) sa_restorer.
Seems reasonable to have all command wrappers in the same place
v2:
Dont move SetInherit
v3:
Comment spelling fix
Adjust WARN0 comment
Remove spurious #include movement
Don't include sys/types.h
Combine virExec enums
Signed-off-by: Cole Robinson <crobinso@redhat.com>
Coverity complained that infd could be -1 at the point where it is
passed to write, when in reality, this code can only be reached if
infd is non-negative.
* src/util/command.c (virCommandProcessIO): Help out coverity.
Detected by Coverity. While it is possible on OOM condition, as
well as with bad code that passes binary == NULL, it is unlikely
to be encountered in the wild.
* src/util/command.c (virCommandNewArgList): Don't leak memory.
Allow the parent process to perform a bi-directional handshake
with the child process during fork/exec. The child process
will fork and do its initial setup. Immediately prior to the
exec(), it will stop & wait for a handshake from the parent
process. The parent process will spawn the child and wait
until the child reaches the handshake point. It will do
whatever extra setup work is required, before signalling the
child to continue.
The implementation of this is done using two pairs of blocking
pipes. The first pair is used to block the parent, until the
child writes a single byte. Then the second pair pair is used
to block the child, until the parent confirms with another
single byte.
* src/util/command.c, src/util/command.h,
src/libvirt_private.syms: Add APIs to perform a handshake
Mingw execve() has a broken signature. Disable this
function until gnulib fixes the signature, since we
don't really need this on Win32 anyway.
* src/util/command.c: Disable virCommandExec on Win32
These VIR_XXXX0 APIs make us confused, use the non-0-suffix APIs instead.
How do these coversions works? The magic is using the gcc extension of ##.
When __VA_ARGS__ is empty, "##" will swallow the "," in "fmt," to
avoid compile error.
example: origin after CPP
high_level_api("%d", a_int) low_level_api("%d", a_int)
high_level_api("a string") low_level_api("a string")
About 400 conversions.
8 special conversions:
VIR_XXXX0("") -> VIR_XXXX("msg") (avoid empty format) 2 conversions
VIR_XXXX0(string_literal_with_%) -> VIR_XXXX(%->%%) 0 conversions
VIR_XXXX0(non_string_literal) -> VIR_XXXX("%s", non_string_literal)
(for security) 6 conversions
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Actually execs the argv/env we've generated, replacing the current process.
Kind of has a limited usage, but allows us to use virCommand in LXC
driver to launch the 'init' process
Sometimes, an asynchronous helper is started (such as a compressor
or iohelper program), but a later error means that we want to
abort that child. Make this easier.
Note that since daemons and virCommandRunAsync can't mix, the only
time virCommandFree can reap a process is if someone did
virCommandRunAsync for a non-daemon and didn't stash the pid.
* src/util/command.h (virCommandAbort): New prototype.
* src/util/command.c (_virCommand): Add new field.
(virCommandRunAsync, virCommandWait): Track whether pid was used.
(virCommandFree): Reap child if caller did not request pid.
(virCommandAbort): New function.
* src/libvirt_private.syms (command.h): Export it.
* tests/commandtest.c (test19): New test.
It doesn't make sense to run a daemon without synchronously
waiting for the child process to reply whether the daemon has
been kicked off and pidfile written yet.
* src/util/command.c (VIR_EXEC_RUN_SYNC): New constant.
(virCommandRun): Set temporary flag.
(virCommandRunAsync): Use it to prevent async runs of intermediate
child when spawning asynchronous daemon grandchild.
Child processes don't always reach _exit(); if they die from a
signal, then any messages should still be accurate. Most users
either expect a 0 status (thankfully, if status==0, then
WIFEXITED(status) is true and WEXITSTATUS(status)==0 for all
known platforms) or were filtering on WIFEXITED before printing
a status, but a few were missing this check. Additionally,
nwfilter_ebiptables_driver was making an assumption that works
on Linux (where WEXITSTATUS shifts and WTERMSIG just masks)
but fails on other platforms (where WEXITSTATUS just masks and
WTERMSIG shifts).
* src/util/command.h (virCommandTranslateStatus): New helper.
* src/libvirt_private.syms (command.h): Export it.
* src/util/command.c (virCommandTranslateStatus): New function.
(virCommandWait): Use it to also diagnose status from signals.
* src/security/security_apparmor.c (load_profile): Likewise.
* src/storage/storage_backend.c
(virStorageBackendQEMUImgBackingFormat): Likewise.
* src/util/util.c (virExecDaemonize, virRunWithHook)
(virFileOperation, virDirCreate): Likewise.
* daemon/remote.c (remoteDispatchAuthPolkit): Likewise.
* src/nwfilter/nwfilter_ebiptables_driver.c (ebiptablesExecCLI):
Likewise.
The virCommandNewArgs() method would free the virCommandPtr
if it failed to add the args. This meant errors reported in
virCommandAddArgSet() were lost. Simply removing the check
for errors from the constructor means they can be reported
correctly later
The virCommandAddEnvPassCommon() method failed to check for
errors before reallocating the cmd->env array, causing a
potential SEGV if cmd was NULL
The virCommandAddArgSet() method needs to validate that at
least 1 element in 'val's parameter is non-NULL, otherwise
code like
cmd = virCommandNew(binary)
virCommandAddAtg(cmd, "foo")
Would end up trying todo execve("foo"), if binary was
NULL.
clang had 5 reports against virCommand; three were false positives
(a NULL deref in ProcessIO solved by sa_assert, and two uninitialized
memory operations solved by adding an initializer), but two were real.
* src/util/command.c (virCommandProcessIO): Fix real bug of
possible NULL dereference. Teach clang that buf is never NULL.
(virCommandRun): Teach clang that infd is only ever accessed when
initialized.
Guarantee that outbuf/errbuf are allocated on success, even if to the
empty string. Caller always has to free the result, and empty output
check requires checking if *outbuf=='\0'. Makes the API easier to use
safely. Failure is best effort allocation (some paths, like
out-of-memory, cannot allocate a buffer, but most do), so caller must
free buffer on failure.
* docs/internals/command.html.in: Update documentation.
* src/util/command.c (virCommandSetOutputBuffer)
(virCommandSetErrorBuffer, virCommandProcessIO) Guarantee empty
string on no output.
* tests/commandtest.c (test17): New test.
* docs/internals/command.html.in: Better documentation of buffer
vs. fd considerations.
* src/util/command.c (virCommandRunAsync): Reject raw execution
with string io.
(virCommandRun): Reject execution with user-specified fds not
visiting a regular file.
"virCommandRun": if "cmd->outbuf" or "cmd->errbuf" is NULL,
libvirtd will be crashed when trying to start a qemu domain
(which invokes "virCommandRun"), it caused by we try to use
"*cmd->outbuf" and "*cmd->errbuf" regardless of cmd->outbuf
or cmd->errbuf is NULL.
* src/util/command.c (virCommandRun)
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.
