On 09/05/2017 10:51 PM, John Ferlan wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1471225
Commit id '99a2d6af2' was a bit too aggressive with determining whether the provided path was a "physical" cd-rom in order to generate a taint message due to the possibility of some guest and host trying to control the tray. For cd-rom guest devices backed to some VIR_STORAGE_TYPE_FILE storage, this wouldn't be a problem and as such it shouldn't be a problem for guest devices using some sort of block device on the host such as iSCSI, LVM, or a Disk pool would present.
Signed-off-by: John Ferlan <jferlan@redhat.com> --- src/libvirt_private.syms | 1 + src/qemu/qemu_domain.c | 2 +- src/util/virfile.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ src/util/virfile.h | 4 ++++ 4 files changed, 54 insertions(+), 1 deletion(-)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index f30a04b..0354568 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1680,6 +1680,7 @@ virFileGetMountSubtree; virFileHasSuffix; virFileInData; virFileIsAbsPath; +virFileIsCDROM; virFileIsDir; virFileIsExecutable; virFileIsLink; diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 9cff501..426c577 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -4807,7 +4807,7 @@ void qemuDomainObjCheckDiskTaint(virQEMUDriverPtr driver,
if (disk->device == VIR_DOMAIN_DISK_DEVICE_CDROM && virStorageSourceGetActualType(disk->src) == VIR_STORAGE_TYPE_BLOCK && - disk->src->path) + disk->src->path && virFileIsCDROM(disk->src->path)) qemuDomainObjTaint(driver, obj, VIR_DOMAIN_TAINT_CDROM_PASSTHROUGH, logCtxt);
diff --git a/src/util/virfile.c b/src/util/virfile.c index 2f28e83..4c31949 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -4166,3 +4166,51 @@ virFileReadValueString(char **value, const char *format, ...) VIR_FREE(str); return ret; } + + +#if defined(__linux__) + +/* virFileIsCDROM + * @path: Supplied path. + * + * Determine if the path is a CD-ROM path. Typically on Linux systems this + * is either /dev/cdrom or /dev/sr0, so those are easy checks. Still if + * someone is trying to be tricky, we can resolve the link to /dev/cdrom + * and compare it to the resolved link of the supplied @path to compare + * if they're the same. + * + * Returns true if the path is a CDROM, false otherwise. + */ +bool +virFileIsCDROM(const char *path) +{ + bool ret = false; + char *linkpath = NULL; + char *cdrompath = NULL; + + if (STREQ(path, "/dev/cdrom") || STREQ(path, "/dev/sr0")) + return true;
What if I have two CDROMs? /dev/sr0 and /dev/sr1? I'm worried that name match is not sufficient and we need to lstat() and check if the major number (st.st_rdev) is 11 (0xb) (according to Documentation/admin-guide/devices.txt from kernel sources). And even that might be not enough :(
+ + if (virFileResolveLink(path, &linkpath) < 0 || + virFileResolveLink("/dev/cdrom", &cdrompath) < 0) + goto cleanup;
This will only work for cases where /dev/cdrom points to the device in @path. However, if /dev/cdrom is pointing to /dev/sr0 and I'm calling this function over /dev/sr1 (because I have a machine with dozens of CDROMs) this function returns false which is obviously wrong. Michal