fuse: fix pipe_buf_operations

Having this struct in module memory could Oops when if the module is
unloaded while the buffer still persists in a pipe.

Since sock_pipe_buf_ops is essentially the same as fuse_dev_pipe_buf_steal
merge them into nosteal_pipe_buf_ops (this is the same as
default_pipe_buf_ops except stealing the page from the buffer is not
allowed).

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@vger.kernel.org

4 files changed, 26 insertions, 48 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index ef74ad5fd362..fa8cb4b7b8fe 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1296,22 +1296,6 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
         return fuse_dev_do_read(fc, file, &cs, iov_length(iov, nr_segs));
 }
 
-static int fuse_dev_pipe_buf_steal(struct pipe_inode_info *pipe,
-                                   struct pipe_buffer *buf)
-{
-        return 1;
-}
-
-static const struct pipe_buf_operations fuse_dev_pipe_buf_ops = {
-        .can_merge = 0,
-        .map = generic_pipe_buf_map,
-        .unmap = generic_pipe_buf_unmap,
-        .confirm = generic_pipe_buf_confirm,
-        .release = generic_pipe_buf_release,
-        .steal = fuse_dev_pipe_buf_steal,
-        .get = generic_pipe_buf_get,
-};
-
 static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
                                     struct pipe_inode_info *pipe,
                                     size_t len, unsigned int flags)
@@ -1358,7 +1342,11 @@ static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
                 buf->page = bufs[page_nr].page;
                 buf->offset = bufs[page_nr].offset;
                 buf->len = bufs[page_nr].len;
-                buf->ops = &fuse_dev_pipe_buf_ops;
+                /*
+                 * Need to be careful about this.  Having buf->ops in module
+                 * code can Oops if the buffer persists after module unload.
+                 */
+                buf->ops = &nosteal_pipe_buf_ops;
 
                 pipe->nrbufs++;
                 page_nr++;
diff --git a/fs/splice.c b/fs/splice.c
index 46a08f772d7d..12028fa41def 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -555,6 +555,24 @@ static const struct pipe_buf_operations default_pipe_buf_ops = {
         .get = generic_pipe_buf_get,
 };
 
+static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
+                                    struct pipe_buffer *buf)
+{
+        return 1;
+}
+
+/* Pipe buffer operations for a socket and similar. */
+const struct pipe_buf_operations nosteal_pipe_buf_ops = {
+        .can_merge = 0,
+        .map = generic_pipe_buf_map,
+        .unmap = generic_pipe_buf_unmap,
+        .confirm = generic_pipe_buf_confirm,
+        .release = generic_pipe_buf_release,
+        .steal = generic_pipe_buf_nosteal,
+        .get = generic_pipe_buf_get,
+};
+EXPORT_SYMBOL(nosteal_pipe_buf_ops);
+
 static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
                             unsigned long vlen, loff_t offset)
 {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index b8809fef61f5..ab5752692113 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -157,6 +157,8 @@ int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 
+extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
+
 /* for F_SETPIPE_SZ and F_GETPIPE_SZ */
 long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
 struct pipe_inode_info *get_pipe_info(struct file *file);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 06e72d3cdf60..0b5149c5bc4a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -74,36 +74,6 @@
 struct kmem_cache *skbuff_head_cache __read_mostly;
 static struct kmem_cache *skbuff_fclone_cache __read_mostly;
 
-static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
-                                  struct pipe_buffer *buf)
-{
-        put_page(buf->page);
-}
-
-static void sock_pipe_buf_get(struct pipe_inode_info *pipe,
-                                struct pipe_buffer *buf)
-{
-        get_page(buf->page);
-}
-
-static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
-                               struct pipe_buffer *buf)
-{
-        return 1;
-}
-
-
-/* Pipe buffer operations for a socket. */
-static const struct pipe_buf_operations sock_pipe_buf_ops = {
-        .can_merge = 0,
-        .map = generic_pipe_buf_map,
-        .unmap = generic_pipe_buf_unmap,
-        .confirm = generic_pipe_buf_confirm,
-        .release = sock_pipe_buf_release,
-        .steal = sock_pipe_buf_steal,
-        .get = sock_pipe_buf_get,
-};
-
 /**
  *      skb_panic - private function for out-of-line support
  *      @skb:   buffer
@@ -1830,7 +1800,7 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
                 .partial = partial,
                 .nr_pages_max = MAX_SKB_FRAGS,
                 .flags = flags,
-                .ops = &sock_pipe_buf_ops,
+                .ops = &nosteal_pipe_buf_ops,
                 .spd_release = sock_spd_release,
         };
         struct sk_buff *frag_iter;