If you have a qcow2 file /path1/to/file pointed to by symlink
/path2/symlink, and pass qemu /path2/symlink, then qemu treats
a relative backing file in the qcow2 metadata as being relative
to /path2, not /path1/to. Yes, this means that it is possible
to create a qcow2 file where the choice of WHICH directory and
symlink you access its contents from will then determine WHICH
backing file (if any) you actually find; the results can be
rather screwy, but we have to match what qemu does.
Libvirt and qemu default to creating absolute backing file
names, so most users don't hit this. But at least VDSM uses
symlinks and relative backing names alongside the
--reuse-external flags to libvirt snapshot operations, with the
result that libvirt was failing to follow the intended chain of
backing files, and then backing files were not granted the
necessary sVirt permissions to be opened by qemu.
See https://bugzilla.redhat.com/show_bug.cgi?id=903248 for
more gory details. This fixes a regression introduced in
commit 8250783.
I tested this patch by creating the following chain:
ls /home/eblake/Downloads/Fedora.iso # raw file for base
cd /var/lib/libvirt/images
qemu-img create -f qcow2 \
-obacking_file=/home/eblake/Downloads/Fedora.iso,backing_fmt=raw one
mkdir sub
cd sub
ln -s ../one onelink
qemu-img create -f qcow2 \
-obacking_file=../sub/onelink,backing_fmt=qcow2 two
mv two ..
ln -s ../two twolink
qemu-img create -f qcow2 \
-obacking_file=../sub/twolink,backing_fmt=qcow2 three
mv three ..
ln -s ../three threelink
then pointing my domain at /var/lib/libvirt/images/sub/threelink.
Prior to this patch, I got complaints about missing backing
files; afterwards, I was able to verify that the backing chain
(and hence DAC and SELinux relabels) of the entire chain worked.
* src/util/virstoragefile.h (_virStorageFileMetadata): Add
directory member.
* src/util/virstoragefile.c (absolutePathFromBaseFile): Drop,
replaced by...
(virFindBackingFile): ...better function.
(virStorageFileGetMetadataInternal): Add an argument.
(virStorageFileGetMetadataFromFD, virStorageFileChainLookup)
(virStorageFileGetMetadata): Update callers.
Prior to this patch, we had the callchains:
external users
\-> virStorageFileGetMetadataFromFD
\-> virStorageFileGetMetadataFromBuf
virStorageFileGetMetadataRecurse
\-> virStorageFileGetMetadataFromFD
\-> virStorageFileGetMetadataFromBuf
However, a future patch wants to add an additional parameter to
the bottom of the chain, for use by virStorageFileGetMetadataRecurse,
without affecting existing external callers. Since there is only a
single caller of the internal function, we can repurpose it to fit
our needs, with this patch giving us:
external users
\-> virStorageFileGetMetadataFromFD
\-> virStorageFileGetMetadataInternal
virStorageFileGetMetadataRecurse /
\-> virStorageFileGetMetadataInternal
* src/util/virstoragefile.c (virStorageFileGetMetadataFromFD):
Move most of the guts...
(virStorageFileGetMetadataFromBuf): ...here, and rename...
(virStorageFileGetMetadataInternal): ...to this.
(virStorageFileGetMetadataRecurse): Use internal helper.
virStorageFileGetMetadataFromFD is the only caller of
virStorageFileGetMetadataFromBuf; and it doesn't care about the
difference between a return of 0 (total success) or 1
(metadata was inconsistent, but pointer was populated as best
as possible); only about a return of -1 (could not read metadata
or out of memory). Changing the return type, and normalizing
the variable names used, will make merging the functions easier
in the next commit.
* src/util/virstoragefile.c (virStorageFileGetMetadataFromBuf):
Change return value, and rename some variables.
(virStorageFileGetMetadataFromFD): Rename some variables.
No semantic change; done so the next patch doesn't need a forward
declaration of a static function.
* src/util/virstoragefile.c (virStorageFileProbeFormatFromBuf):
Hoist earlier.
CC libvirt_util_la-vircommand.lo
../../src/util/vircommand.c:2358:1: error: 'virCommandHandshakeChild' defined but not used [-Werror=unused-function]
The function is only implemented inside #ifndef WIN32.
* src/util/vircommand.c (virCommandHandshakeChild): Hoist earlier,
so that win32 build doesn't hit an unused forward declaration.
virCommand was previously calling virSetUIDGID() to change the uid and
gid of the child process, then separately calling
virSetCapabilities(). This did not work if the desired uid was != 0,
since a setuid to anything other than 0 normally clears all
capabilities bits.
The solution is to use the new virSetUIDGIDWithCaps(), sending it the
uid, gid, and capabilities bits. This will get the new process setup
properly.
Since the static functions virSetCapabilities() and
virClearCapabilities are no longer called, they have been removed.
NOTE: When combined with "filecap $path-to-qemu sys_rawio", this patch
will make CAP_SYS_RAWIO (which is required for passthrough of generic
scsi commands to a guest - see commits e8daeeb, 177db08, 397e6a7, and
74e0349) be retained by qemu when necessary. Apparently that
capability has been broken for non-root qemu ever since it was
originally added.
Normally when a process' uid is changed to non-0, all the capabilities
bits are cleared, even those explicitly set with calls to
capng_update()/capng_apply() made immediately before setuid. And
*after* the process' uid has been changed, it no longer has the
necessary privileges to add capabilities back to the process.
In order to set a non-0 uid while still maintaining any capabilities
bits, it is necessary to either call capng_change_id() (which
unfortunately doesn't currently call initgroups to setup auxiliary
group membership), or to perform the small amount of calisthenics
contained in the new utility function virSetUIDGIDWithCaps().
Another very important difference between the capabilities
setting/clearing in virSetUIDGIDWithCaps() and virCommand's
virSetCapabilities() (which it will replace in the next patch) is that
the new function properly clears the capabilities bounding set, so it
will not be possible for a child process to set any new
capabilities.
A short description of what is done by virSetUIDGIDWithCaps():
1) clear all capabilities then set all those desired by the caller (in
capBits) plus CAP_SETGID, CAP_SETUID, and CAP_SETPCAP (which is needed
to change the capabilities bounding set).
2) call prctl(), telling it that we want to maintain current
capabilities across an upcoming setuid().
3) switch to the new uid/gid
4) again call prctl(), telling it we will no longer want capabilities
maintained if this process does another setuid().
5) clear the capabilities that we added to allow us to
setuid/setgid/change the bounding set (unless they were also requested
by the caller via the virCommand API).
Because the modification/maintaining of capabilities is intermingled
with setting the uid, this is necessarily done in a single function,
rather than having two independent functions.
Note that, due to the way that effective capabilities are computed (at
time of execve) for a process that has uid != 0, the *file*
capabilities of the binary being executed must also have the desired
capabilities bit(s) set (see "man 7 capabilities"). This can be done
with the "filecap" command. (e.g. "filecap /usr/bin/qemu-kvm sys_rawio").
This is an interim measure to make sure everything still works in this
order. The next step will be to perform capabilities drop and
setuid/gid as a single operation (which is the only way to keep any
capabilities when switching to a non-root uid).
virCommand gets two new APIs: virCommandSetSELinuxLabel() and
virCommandSetAppArmorProfile(), which both save a copy of a
null-terminated string in the virCommand. During virCommandRun, if the
string is non-NULL and we've been compiled with AppArmor and/or
SELinux security driver support, the appropriate security library
function is called for the child process, using the string that was
previously set. In the case of SELinux, setexeccon_raw() is called,
and for AppArmor, aa_change_profile() is called.
This functionality has been added so that users of virCommand can use
the upcoming virSecurityManagerSetChildProcessLabel() prior to running
a child process, rather than needing to setup a hook function to be
called (and in turn call virSecurityManagerSetProcessLabel()) *during*
the setup of the child process.
Rather than treating uid:gid of 0:0 as a NOP, we blindly pass that
through to the lower layers. However, we *do* check for a requested
value of "-1" to mean "don't change this setting". setregid() and
setreuid() already interpret -1 as a NOP, so this is just an
optimization, but we are also calling getpwuid_r and initgroups, and
it's unclear what the former would do with a uid of -1.
If a uid and/or gid is specified for a command, it will be set just
after the user-supplied post-fork "hook" function is called.
The intent is that this can replace user hook functions that set
uid/gid. This moves the setting of uid/gid and dropping of
capabilities closer to each other, which is important since the two
should really be done at the same time (libcapng provides a single
function that does both, which we will be unable to use, but want to
mimic as closely as possible).
All args except "cmd" in the call to virExec are now redundant, since
they can all be found in cmd, so remove the args and reference the
data directly in cmd. One exception to this is that "infd" was being
modified within virExec, and modifying the original in cmd caused make
check failures, so cmd->infd is copied to a local, and the local is
used during virExec().
virExecWithHook is only called from one place, so it always has the
same "hook" function (virHookCommand), and the data sent to that
function is always a virCommandPtr, so eliminate the function and
generic data from the arglist, and replace it with "virCommandPtr
cmd". The call to (hook)(data) is replaced with
"virHookCommand(cmd)". Finally, virExecWithHook is renamed to virExec.
Indentation has been updated only for code that will remain after the
next patch, which will remove all other args to virExec (since they
are now redundant, as they're all members of virCommandPtr).
Currently, if a command wants to do asynchronous IO, a callback
is registered in the libvirtd eventloop to handle writes and
reads. However, there's a race in virCommandWait. The eventloop
may already be executing the callback, while virCommandWait is
mangling internal state of virCommand. To deal with it, we need
to either introduce locking or spawn a separate thread where we
poll() on stdio from child. The former, however, requires to
unlock all mutexes held, as the event loop may execute other
callbacks which tries to lock one of the mutexes, deadlock and
thus never wake us up. So it's safer to spawn a separate thread.
This makes code easier to read, by avoiding lines longer than
80 columns and removing the repetition from the callers.
* src/util/virstoragefile.c (qedGetHeaderUL, qedGetHeaderULL):
Delete in favor of more generic macros.
(qcow2GetBackingStoreFormat, qcowXGetBackingStore)
(qedGetBackingStore, virStorageFileMatchesVersion)
(virStorageFileGetMetadataInternal): Use new macros.
* src/cpu/cpu_x86.c (x86VendorLoad): Likewise.
We have several cases where we need to read endian-dependent
data regardless of host endianness; rather than open-coding
these call sites, it will be nicer to funnel things through
a macro.
The virendian.h file can be expanded to add writer functions,
and/or 16-bit access patterns, if needed. Also, if we need
to turn things into a function to avoid multiple evaluations
of buf, that can be done later. But for now, a macro worked.
* src/util/virendian.h: New file.
* src/Makefile.am (UTIL_SOURCES): Ship it.
* tests/virendiantest.c: New test.
* tests/Makefile.am (test_programs, virendiantest_SOURCES): Run
the test.
* .gitignore: Ignore built file.
Instead of creating an iptables command in one shot, do it in steps
so we can add conditional options like physdev and protocol.
This removes code duplication while keeping existing behaviour.
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Eric Blake <eblake@redhat.com>
We are requesting for stderr catching for all cases in
virFileWrapperFdNew(). There is no need to have a separate
function just to report an error, esp. when we can do it in
virFileWrapperFdClose().
We had an easy way to iterate set bits, but not for iterating
cleared bits.
* src/util/virbitmap.h (virBitmapNextClearBit): New prototype.
* src/util/virbitmap.c (virBitmapNextClearBit): Implement it.
* src/libvirt_private.syms (bitmap.h): Export it.
* tests/virbitmaptest.c (test4): Test it.
To allow modifications to the lists to be synchronized, convert
virPCIDeviceList and virUSBDeviceList into virObjectLockable
classes. The locking, however, will not be self-contained. The
users of these classes will have to call virObjectLock/Unlock
in the critical regions.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Commit 34e8f63a32 introduced support for catching errors from
libvirt iohelper. However, at those times there wasn't such fancy
API as virCommandDoAsyncIO(), so everything has to be implemented
on our own. But since we do have the API now, we can use it and
drop our implementation then.
Currently, if we want to feed stdin, or catch stdout or stderr of a
virCommand we have to use virCommandRun(). When using virCommandRunAsync()
we have to register FD handles by hand. This may lead to code duplication.
Hence, introduce an internal API, which does this automatically within
virCommandRunAsync(). The intended usage looks like this:
virCommandPtr cmd = virCommandNew*(...);
char *buf = NULL;
...
virCommandSetOutputBuffer(cmd, &buf);
virCommandDoAsyncIO(cmd);
if (virCommandRunAsync(cmd, NULL) < 0)
goto cleanup;
...
if (virCommandWait(cmd, NULL) < 0)
goto cleanup;
/* @buf now contains @cmd's stdout */
VIR_DEBUG("STDOUT: %s", NULLSTR(buf));
...
cleanup:
VIR_FREE(buf);
virCommandFree(cmd);
Note, that both stdout and stderr buffers may change until virCommandWait()
returns.
QEMU is fully capable of handling VDI images and we just refuse to
work with them. As qemu-img knows and supports this, there should be
no problem with this addition.
This is of course, just basic functionality, without searching for any
backing files, etc.
Some files have the magic shifted to some offset other than 0, so we
have to support that. I also cleaned up some lines to be more
readable and added missing magic for iso file format.
Commit 6094ad7b (0.9.3 release) promoted several functions from
internal to public, but forgot to fix the documentation generator
to provide details about those functions.
For an example of what this fixes, look at:
file:///path/to/libvirt/docs/html/libvirt-libvirt.html#virEventAddHandle
before and after the patch.
* docs/apibuild.py (ignored_functions): Don't ignore functions
that were turned into official API.
* src/util/virevent.c: Fix comments to pass through parser.
Way back when I started making changes for Coverity messages my first set
were to a bunch of CHECKED_RETURN errors. In particular virAsprintf() had
a few callers that Coverity noted didn't check their return (although some
did check if the buffer being printed to was NULL or not).
It was suggested at the time as a further patch an ATTRIBUTE_RETURN_CHECK
should be added to virAsprintf(), see:
https://www.redhat.com/archives/libvir-list/2013-January/msg00120.html
This patch does that and fixes a few more instances not found by Coverity
that failed the check.
Setting the log output prefix to 0 is not supported and in fact results
in the following message:
warning : virLogParseOutputs:1021 : Ignoring invalid log output setting.
This patch changes the name of the @sep argument to @terminator and
clarifies it's usage. This patch also explicitly documents that
whitespace can't be used as @terminator as it is skipped multiple times
in the implementation.
When building with static analysis enabled, we turn on attribute
nonnull checking. However, this caused the build to fail with:
../../src/util/virobject.c: In function 'virObjectOnceInit':
../../src/util/virobject.c:55:40: error: null argument where non-null required (argument 1) [-Werror=nonnull]
Creation of the virObject class is the one instance where the
parent class is allowed to be NULL. Making things conditional
will let us keep static analysis checking for all other .c file
callers, without breaking the build on this one exception.
* src/util/virobject.c: Define witness.
* src/util/virobject.h (virClassNew): Use it to force most callers
to pass non-null parameter.
The Coverity static analyzer was generating many false positives for the
unary operation inside the VIR_FREE() definition as it was trying to evaluate
the else portion of the "?:" even though the if portion was (1).
Signed-off-by: Eric Blake <eblake@redhat.com>
Currently, whenever somebody calls saferead() on nonblocking FD
(safewrite() is totally interchangeable for purpose of this message)
he might get wrong return value. For instance, in the first iteration
some data is read. The number of bytes read is stored into local
variable 'nread'. However, in next iterations we can get -1 from
read() with errno == EAGAIN, in which case the -1 is returned despite
fact some data has already been read. So the caller gets confused.
Bare read() should be used for nonblocking FD.
Working with virTypedParameters in clients written in C is ugly and
requires all clients to duplicate the same code. This set of APIs makes
this code for manipulating with virTypedParameters integral part of
libvirt so that all clients may benefit from it.
A build on FreeBSD failed with:
util/virportallocator.c:108: error: storage size of 'addr' isn't known
util/virportallocator.c:123: error: 'INADDR_ANY' undeclared (first use in this function)
It turns out that while POSIX allows sockaddr_in to leak in through
<arpa/inet.h> (the way Linux does it), it is not mandatory, and
conforming applications are required to get it through <netinet/in.h>.
* src/util/virportallocator.c: Include header for struct
sockaddr_in.
* tests/virportallocatortest.c: Likewise.
The QEMU driver default max port is 65535, but it then increments
this by 1 to 65536. This maps to 0 in an unsigned short :-( This
was apparently done so that for() loops could use "< max" instead
of "<= max". Remove this insanity and just make the loop do the
right thing.
