fs: prevent page refcount overflow in pipe_buf_get

Change pipe_buf_get() to return a bool indicating whether it succeeded
in raising the refcount of the page (if the thing in the pipe is a page).
This removes another mechanism for overflowing the page refcount.  All
callers converted to handle a failure.

Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 809c0f2f9942e372d67ddd7e45e6cee2b344414b..64f4de9834687abd7fa9ccc2c282f0ac019f5917 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -2034,10 +2034,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
                rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
 
        ret = -EINVAL;
-       if (rem < len) {
-               pipe_unlock(pipe);
-               goto out;
-       }
+       if (rem < len)
+               goto out_free;
 
        rem = len;
        while (rem) {
@@ -2055,7 +2053,9 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
                        pipe->nrbufs--;
                } else {
-                       pipe_buf_get(pipe, ibuf);
+                       if (!pipe_buf_get(pipe, ibuf))
+                               goto out_free;
+
                        *obuf = *ibuf;
                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
                        obuf->len = rem;
@@ -2078,11 +2078,11 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
        ret = fuse_dev_do_write(fud, &cs, len);
 
        pipe_lock(pipe);
+out_free:
        for (idx = 0; idx < nbuf; idx++)
                pipe_buf_release(pipe, &bufs[idx]);
        pipe_unlock(pipe);
 
-out:
        kvfree(bufs);
        return ret;
 }

diff --git a/fs/pipe.c b/fs/pipe.c
index bdc5d3c0977d09b37d5eb80abfb92c3a336f6c92..b1543b85c14a4427a8659f1656ea140cd913f9e6 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -189,9 +189,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal);
  *     in the tee() system call, when we duplicate the buffers in one
  *     pipe into another.
  */
-void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
+bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 {
-       get_page(buf->page);
+       return try_get_page(buf->page);
 }
 EXPORT_SYMBOL(generic_pipe_buf_get);
 

diff --git a/fs/splice.c b/fs/splice.c
index de2ede048473cef81bec9161cf1842b70835ea63..f30af82b850dd339056de3e2ca62dcb1ad121458 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1588,7 +1588,11 @@ retry:
                         * Get a reference to this pipe buffer,
                         * so we can copy the contents over.
                         */
-                       pipe_buf_get(ipipe, ibuf);
+                       if (!pipe_buf_get(ipipe, ibuf)) {
+                               if (ret == 0)
+                                       ret = -EFAULT;
+                               break;
+                       }
                        *obuf = *ibuf;
 
                        /*
@@ -1660,7 +1664,11 @@ static int link_pipe(struct pipe_inode_info *ipipe,
                 * Get a reference to this pipe buffer,
                 * so we can copy the contents over.
                 */
-               pipe_buf_get(ipipe, ibuf);
+               if (!pipe_buf_get(ipipe, ibuf)) {
+                       if (ret == 0)
+                               ret = -EFAULT;
+                       break;
+               }
 
                obuf = opipe->bufs + nbuf;
                *obuf = *ibuf;

diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 5a3bb3b7c9ad3fb287e3133d81cd52b0def6bdde..3f2a42c11e206e7702aae43021a4d25792039aaa 100644 (file)
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -108,18 +108,20 @@ struct pipe_buf_operations {
        /*
         * Get a reference to the pipe buffer.
         */
-       void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
+       bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 };
 
 /**
  * pipe_buf_get - get a reference to a pipe_buffer
  * @pipe:      the pipe that the buffer belongs to
  * @buf:       the buffer to get a reference to
+ *
+ * Return: %true if the reference was successfully obtained.
  */
-static inline void pipe_buf_get(struct pipe_inode_info *pipe,
+static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
                                struct pipe_buffer *buf)
 {
-       buf->ops->get(pipe, buf);
+       return buf->ops->get(pipe, buf);
 }
 
 /**
@@ -178,7 +180,7 @@ struct pipe_inode_info *alloc_pipe_info(void);
 void free_pipe_info(struct pipe_inode_info *);
 
 /* Generic pipe buffer ops functions */
-void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
+bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 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 *);

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c4238b441624415cfd6113bb36ea5d71b6eaaa54..0f300d488c9ff7690dfb76ff0a71411a3e8ef741 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6835,12 +6835,16 @@ static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
        buf->private = 0;
 }
 
-static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
+static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
                                struct pipe_buffer *buf)
 {
        struct buffer_ref *ref = (struct buffer_ref *)buf->private;
 
+       if (ref->ref > INT_MAX/2)
+               return false;
+
        ref->ref++;
+       return true;
 }
 
 /* Pipe buffer operations for a buffer. */