From 38d78e587d4960d0db94add518d27ee74bad2301 Mon Sep 17 00:00:00 2001 From: Vladimir Davydov Date: Fri, 22 Mar 2013 15:04:51 -0700 Subject: mqueue: sys_mq_open: do not call mnt_drop_write() if read-only mnt_drop_write() must be called only if mnt_want_write() succeeded, otherwise the mnt_writers counter will diverge. mnt_writers counters are used to check if remounting FS as read-only is OK, so after an extra mnt_drop_write() call, it would be impossible to remount mqueue FS as read-only. Besides, on umount a warning would be printed like this one: ===================================== [ BUG: bad unlock balance detected! ] 3.9.0-rc3 #5 Not tainted ------------------------------------- a.out/12486 is trying to release lock (sb_writers) at: mnt_drop_write+0x1f/0x30 but there are no more locks to release! Signed-off-by: Vladimir Davydov Cc: Doug Ledford Cc: KOSAKI Motohiro Cc: "Eric W. Biederman" Cc: Al Viro Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/mqueue.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'ipc/mqueue.c') diff --git a/ipc/mqueue.c b/ipc/mqueue.c index e5c4f609f22c..3953fda2e8bd 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -840,7 +840,8 @@ out_putfd: fd = error; } mutex_unlock(&root->d_inode->i_mutex); - mnt_drop_write(mnt); + if (!ro) + mnt_drop_write(mnt); out_putname: putname(name); return fd; -- cgit v1.2.3 From a636b702ed1805e988ad3d8ff8b52c060f8b341c Mon Sep 17 00:00:00 2001 From: Eric W. Biederman Date: Thu, 21 Mar 2013 18:13:15 -0700 Subject: ipc: Restrict mounting the mqueue filesystem Only allow mounting the mqueue filesystem if the caller has CAP_SYS_ADMIN rights over the ipc namespace. The principle here is if you create or have capabilities over it you can mount it, otherwise you get to live with what other people have mounted. This information is not particularly sensitive and mqueue essentially only reports which posix messages queues exist. Still when creating a restricted environment for an application to live any extra information may be of use to someone with sufficient creativity. The historical if imperfect way this information has been restricted has been not to allow mounts and restricting this to ipc namespace creators maintains the spirit of the historical restriction. Cc: stable@vger.kernel.org Acked-by: Serge Hallyn Signed-off-by: "Eric W. Biederman" --- ipc/mqueue.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'ipc/mqueue.c') diff --git a/ipc/mqueue.c b/ipc/mqueue.c index e5c4f609f22c..c4ae32ec6c6b 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -330,8 +330,16 @@ static struct dentry *mqueue_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { - if (!(flags & MS_KERNMOUNT)) - data = current->nsproxy->ipc_ns; + if (!(flags & MS_KERNMOUNT)) { + struct ipc_namespace *ns = current->nsproxy->ipc_ns; + /* Don't allow mounting unless the caller has CAP_SYS_ADMIN + * over the ipc namespace. + */ + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + + data = ns; + } return mount_ns(fs_type, flags, data, mqueue_fill_super); } -- cgit v1.2.3