On 18.12.2013 15:33, Reco wrote:
Hello, list.
I was pointed here by maintainer of libvirt package in Debian, Guido Günther. For the sake of completeness, the original bug report can be viewed at this link:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=732394
To sum up the bug report, current implementation of virInitctlSetRunLevel function (src/util/virinitctl.c) lacks any sanity checks before writing to container's /dev/initctl. In the absence of such checks, libvirtd can be easily tricked to write runlevel check request to an arbitrary main hosts' file (including hosts' /run/initctl, as described in the bug report). All it takes is one symlink in place of containers' /dev/initctl.
I've checked current libvirtd's git, and it seems to me that the problem is still here.
Attached to this letter is a patch which tries to mitigate the issue by checking whenever container's /dev/initctl is a pipe actually.
Sincerely yours, Reco
PS I'm not subscribed to this list, in case of further questions please CC me.
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[Pasting the patch here]
--- a/src/util/virinitctl.c 2013-12-18 11:13:10.078432196 +0400 +++ b/src/util/virinitctl.c 2013-12-18 11:26:50.000000000 +0400 @@ -24,7 +24,10 @@ #include <config.h>
#include <sys/param.h> +#include <sys/types.h> +#include <sys/stat.h> #include <fcntl.h> +#include <unistd.h>
#include "internal.h" #include "virinitctl.h" @@ -122,6 +125,7 @@ int fd = -1; char *path = NULL; int ret = -1; + struct stat attrs;
memset(&req, 0, sizeof(req));
@@ -139,7 +143,10 @@ return -1; }
- if ((fd = open(path, O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY)) < 0) { + if (lstat(path, &attrs) == -1) + goto cleanup;
While the part above looks okay, I think we should report error if the /dev/initctl is not a pipe. Moreover, with your approach, if it's really not a pipe, we don't call open() and proceed to safewrite(-1, ...) at line 153 which will report EBADF error.
+ + if ((attrs.st_mode & S_IFIFO) && (fd = open(path, O_WRONLY|O_NONBLOCK|O_CLOEXEC|O_NOCTTY)) < 0) { if (errno == ENOENT) { ret = 0; goto cleanup
Missing ';' at EOL ^^^ - I guess you missed that during copy-paste. Looking forward to v2. BTW: consider using git when sending patches. I couldn't really apply this patch via 'git am'. http://libvirt.org/hacking.html#patches Michal