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authorEric W. Biederman <ebiederm@xmission.com>2016-05-20 17:22:48 -0500
committerDavid S. Miller <davem@davemloft.net>2016-05-20 19:45:40 -0400
commite27f4a942a0ee4b84567a3c6cfa84f273e55cbb7 (patch)
tree3be25bbf26d34827d5cd8100f3012a8758a9c771 /kernel/bpf
parent56025caa821d8e398b7cff2c45fb1e3e769549d7 (diff)
downloadlinux-sh-e27f4a942a0ee4b84567a3c6cfa84f273e55cbb7.tar.gz
bpf: Use mount_nodev not mount_ns to mount the bpf filesystem
While reviewing the filesystems that set FS_USERNS_MOUNT I spotted the bpf filesystem. Looking at the code I saw a broken usage of mount_ns with current->nsproxy->mnt_ns. As the code does not acquire a reference to the mount namespace it can not possibly be correct to store the mount namespace on the superblock as it does. Replace mount_ns with mount_nodev so that each mount of the bpf filesystem returns a distinct instance, and the code is not buggy. In discussion with Hannes Frederic Sowa it was reported that the use of mount_ns was an attempt to have one bpf instance per mount namespace, in an attempt to keep resources that pin resources from hiding. That intent simply does not work, the vfs is not built to allow that kind of behavior. Which means that the bpf filesystem really is buggy both semantically and in it's implemenation as it does not nor can it implement the original intent. This change is userspace visible, but my experience with similar filesystems leads me to believe nothing will break with a model of each mount of the bpf filesystem is distinct from all others. Fixes: b2197755b263 ("bpf: add support for persistent maps/progs") Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/inode.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 71b75d9c81da..04be7021f848 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -357,7 +357,7 @@ static int bpf_fill_super(struct super_block *sb, void *data, int silent)
static struct dentry *bpf_mount(struct file_system_type *type, int flags,
const char *dev_name, void *data)
{
- return mount_ns(type, flags, current->nsproxy->mnt_ns, bpf_fill_super);
+ return mount_nodev(type, flags, data, bpf_fill_super);
}
static struct file_system_type bpf_fs_type = {