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qemu: Move 'shmem' device size validation to qemu_validate 

The 'size' of a 'shmem' device is parsed and formatted as a "scaled"
value, stored in bytes, but the formatting scale is mebibytes. This
precission loss combined with the fact that the value was validated only
when starting and the size is formatted only when non-zero meant that
on first parse a value < 1 MiB would be accepted, but would be formatted
to the XML as 0 MiB as it was non-zero but truncated and a subsequent
parse would parse of such XML would parse it as 0 bytes, which in turn
would be interpreted as 'default' size.

Fix the issue by moving the validator, which ensures that the number is
a power of two and more than 1 MiB to the validator code so that it'll
be rejected at XML parsing time.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Peter Krempa 2023-12-19 00:16:29 +01:00
parent deb3c834e5
commit 7dd3d77940
7 changed files with 13 additions and 91 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/qemu/qemu_command.c
View File

@ -9086,25 +9086,6 @@ qemuBuildShmemCommandLine(virCommand *cmd,
g_autoptr(virJSONValue) memProps = NULL;
g_autoptr(virJSONValue) devProps = NULL;
if (shmem->size) {
/*
* Thanks to our parsing code, we have a guarantee that the
* size is power of two and is at least a mebibyte in size.
* But because it may change in the future, the checks are
* doubled in here.
*/
if (shmem->size & (shmem->size - 1)) {
virReportError(VIR_ERR_XML_ERROR, "%s",
_("shmem size must be a power of two"));
return -1;
}
if (shmem->size < 1024 * 1024) {
virReportError(VIR_ERR_XML_ERROR, "%s",
_("shmem size must be at least 1 MiB (1024 KiB)"));
return -1;
}
}
if (shmem->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
_("only 'pci' addresses are supported for the shared memory device"));

9
src/qemu/qemu_validate.c
View File

@ -5118,6 +5118,15 @@ static int
qemuValidateDomainDeviceDefShmem(virDomainShmemDef *shmem,
virQEMUCaps *qemuCaps)
{
if (shmem->size > 0) {
if (shmem->size < 1024 * 1024 ||
!VIR_IS_POW2(shmem->size)) {
virReportError(VIR_ERR_XML_ERROR, "%s",
_("shmem size must be a power of 2 and at least 1 MiB (1024 KiB)"));
return -1;
}
}
switch (shmem->model) {
case VIR_DOMAIN_SHMEM_MODEL_IVSHMEM:
virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",

2
tests/qemuxml2argvdata/shmem-invalid-size.x86_64-latest.err
View File

@ -1 +1 @@
XML error: shmem size must be a power of two
XML error: shmem size must be a power of 2 and at least 1 MiB (1024 KiB)

2
tests/qemuxml2argvdata/shmem-small-size.x86_64-latest.err
View File

@ -1 +1 @@
XML error: shmem size must be at least 1 MiB (1024 KiB)
XML error: shmem size must be a power of 2 and at least 1 MiB (1024 KiB)

34
tests/qemuxml2xmloutdata/shmem-invalid-size.x86_64-latest.xml
View File

@ -1,34 +0,0 @@
<domain type='qemu'>
<name>QEMUGuest1</name>
<uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
<memory unit='KiB'>219136</memory>
<currentMemory unit='KiB'>219136</currentMemory>
<vcpu placement='static'>1</vcpu>
<os>
<type arch='x86_64' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<cpu mode='custom' match='exact' check='none'>
<model fallback='forbid'>qemu64</model>
</cpu>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<controller type='usb' index='0' model='piix3-uhci'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'/>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<audio id='1' type='none'/>
<memballoon model='none'/>
<shmem name='shmem0'>
<model type='ivshmem-plain'/>
<size unit='M'>12</size>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</shmem>
</devices>
</domain>

34
tests/qemuxml2xmloutdata/shmem-small-size.x86_64-latest.xml
View File

@ -1,34 +0,0 @@
<domain type='qemu'>
<name>QEMUGuest1</name>
<uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
<memory unit='KiB'>219136</memory>
<currentMemory unit='KiB'>219136</currentMemory>
<vcpu placement='static'>1</vcpu>
<os>
<type arch='x86_64' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<cpu mode='custom' match='exact' check='none'>
<model fallback='forbid'>qemu64</model>
</cpu>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/bin/qemu-system-x86_64</emulator>
<controller type='usb' index='0' model='piix3-uhci'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'/>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<audio id='1' type='none'/>
<memballoon model='none'/>
<shmem name='shmem0'>
<model type='ivshmem-plain'/>
<size unit='M'>0</size>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</shmem>
</devices>
</domain>

4
tests/qemuxmlconftest.c
View File

@ -2456,9 +2456,9 @@ mymain(void)
DO_TEST_CAPS_ARCH_LATEST_FULL("fips-enabled", "x86_64", ARG_FLAGS, FLAG_FIPS_HOST);
DO_TEST_CAPS_LATEST("shmem-plain-doorbell");
DO_TEST_CAPS_LATEST_FAILURE("shmem-invalid-size");
DO_TEST_CAPS_LATEST_PARSE_ERROR("shmem-invalid-size");
DO_TEST_CAPS_LATEST_FAILURE("shmem-invalid-address");
DO_TEST_CAPS_LATEST_FAILURE("shmem-small-size");
DO_TEST_CAPS_LATEST_PARSE_ERROR("shmem-small-size");
DO_TEST_CAPS_LATEST_PARSE_ERROR("shmem-msi-only");
DO_TEST_CAPS_LATEST("cpu-host-passthrough-features");