On Sat, Dec 02, 2017 at 06:48:50PM +0000, Al Viro wrote:
> On Fri, Dec 01, 2017 at 09:47:00PM +0100, Daniel Borkmann wrote:
>
> > > Might want to replace security_path_mknod() with something saner, while
> > > we are
> > > at it.
> > >
> > > Objections?
> >
> > No, thanks for looking into this, and sorry for this fugly hack! :( Not
> > that this doesn't make it any better, but I think back then I took it
> > over from mqueue implementation ... should have known better and looking
> > into making this generic instead, sigh. The above looks good to me, so
> > no objections from my side and thanks for working on it!
> >
> > > PS: mqueue.c would also benefit from such primitive - do_create() there
> > > would
> > > simply pass attr as callback's argument into vfs_mkobj(), with callback
> > > being
> > > the guts of mqueue_create()...
>
> OK... See vfs.git#untested.mkobj; it really needs testing, though -
> mq_open(2)
> passes LTP tests, but that's not saying much, and BPF side is completely
> untested.
... and FWIW, completely untested patch for net/netfilter/xt_bpf.c follows:
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e55e4255a210..a7000e4775e7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -514,6 +514,9 @@ static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
return bpf_prog_get_type_dev(ufd, type, false);
}
+struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type
type);
+bool bpf_prog_get_ok(struct bpf_prog *, enum bpf_prog_type *, bool);
+
int bpf_prog_offload_compile(struct bpf_prog *prog);
void bpf_prog_offload_destroy(struct bpf_prog *prog);
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 2b75faccc771..9d1050dc2a7a 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -364,6 +364,45 @@ int bpf_obj_get_user(const char __user *pathname, int
flags)
}
EXPORT_SYMBOL_GPL(bpf_obj_get_user);
+static struct bpf_prog *__get_prog_inode(struct inode *inode, enum
bpf_prog_type type)
+{
+ struct bpf_prog *prog;
+ int ret = inode_permission(inode, MAY_READ | MAY_WRITE);
+ if (ret)
+ return ERR_PTR(ret);
+
+ if (inode->i_op == &bpf_map_iops)
+ return ERR_PTR(-EINVAL);
+ if (inode->i_op != &bpf_prog_iops)
+ return ERR_PTR(-EACCES);
+
+ prog = inode->i_private;
+
+ ret = security_bpf_prog(prog);
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ if (!bpf_prog_get_ok(prog, &type, false))
+ return ERR_PTR(-EINVAL);
+
+ return bpf_prog_inc(prog);
+}
+
+struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type
type)
+{
+ struct bpf_prog *prog;
+ struct path path;
+ int ret = kern_path(name, LOOKUP_FOLLOW, &path);
+ if (ret)
+ return ERR_PTR(ret);
+ prog = __get_prog_inode(d_backing_inode(path.dentry), type);
+ if (!IS_ERR(prog))
+ touch_atime(&path);
+ path_put(&path);
+ return prog;
+}
+EXPORT_SYMBOL(bpf_prog_get_type_path);
+
static void bpf_evict_inode(struct inode *inode)
{
enum bpf_type type;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2c4cfeaa8d5e..5cb783fc8224 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1057,7 +1057,7 @@ struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog
*prog)
}
EXPORT_SYMBOL_GPL(bpf_prog_inc_not_zero);
-static bool bpf_prog_get_ok(struct bpf_prog *prog,
+bool bpf_prog_get_ok(struct bpf_prog *prog,
enum bpf_prog_type *attach_type, bool attach_drv)
{
/* not an attachment, just a refcount inc, always allow */
diff --git a/net/netfilter/xt_bpf.c b/net/netfilter/xt_bpf.c
index 041da0d9c06f..fa2ca0a13619 100644
--- a/net/netfilter/xt_bpf.c
+++ b/net/netfilter/xt_bpf.c
@@ -52,18 +52,8 @@ static int __bpf_mt_check_fd(int fd, struct bpf_prog **ret)
static int __bpf_mt_check_path(const char *path, struct bpf_prog **ret)
{
- mm_segment_t oldfs = get_fs();
- int retval, fd;
-
- set_fs(KERNEL_DS);
- fd = bpf_obj_get_user(path, 0);
- set_fs(oldfs);
- if (fd < 0)
- return fd;
-
- retval = __bpf_mt_check_fd(fd, ret);
- sys_close(fd);
- return retval;
+ *ret = bpf_prog_get_type_path(path, BPF_PROG_TYPE_SOCKET_FILTER);
+ return PTR_ERR_OR_ZERO(*ret);
}
static int bpf_mt_check(const struct xt_mtchk_param *par)
