On Tue, Jan 25, 2011 at 04:24:19AM -0500, Laine Stump wrote:
This patch is a partial resolution to the following bug:
https://bugzilla.redhat.com/show_bug.cgi?id=667756
(to complete the fix, an updated selinux-policy package is required, to add the policy that allows libvirt to set the context of a fifo, which was previously not allowed).
Explanation : When an incoming migration is over a pipe (for example, if the image was compressed and is being fed through gzip, or was on a root-squash nfs server, so needed to be opened by a child process running as a different uid), qemu cannot read it unless the selinux context label for the pipe has been set properly.
The solution is to check the fd used as the source of the migration just before passing it to qemu; if it's a fifo (implying that it's a pipe), we call the newly added virSecurityManagerSetFDLabel() function to set the context properly. --- src/qemu/qemu_driver.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 34cc29f..985b062 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -2667,6 +2667,24 @@ static int qemudStartVMDaemon(virConnectPtr conn, vm, stdin_path) < 0) goto cleanup;
+ if (stdin_fd != -1) { + /* if there's an fd to migrate from, and it's a pipe, put the + * proper security label on it + */ + struct stat stdin_sb; + + DEBUG0("setting security label on pipe used for migration"); + + if (fstat(stdin_fd, &stdin_sb) < 0) { + virReportSystemError(errno, + _("cannot stat fd %d"), stdin_fd); + goto cleanup; + } + if (S_ISFIFO(stdin_sb.st_mode) && + virSecurityManagerSetFDLabel(driver->securityManager, vm, stdin_fd) < 0) + goto cleanup; + }
This feels like the wrong place to put this call. The callers of qemudStartVMDaemon() which opened 'stdin_fd' in the first place will already know if it is a pipe or not. If we put the virSecurityManagerSetFDLabel call in the appropriate callers, then the fstat() complexity is avoided. Daniel