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Message-ID: <20140117155330.GH24171@tucsk.piliscsaba.szeredi.hu>
Date: Fri, 17 Jan 2014 16:53:30 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: Al Viro <viro@...IV.linux.org.uk>
Cc: Jens Axboe <axboe@...nel.dk>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [oops?] what protects buf->ops->confirm() from rmmod fuse
unmapping buf->ops?
On Fri, Jan 17, 2014 at 11:48:32AM +0000, Al Viro wrote:
> On Fri, Jan 17, 2014 at 10:49:30AM +0100, Miklos Szeredi wrote:
>
> > Can't we just move the fuse_dev_pipe_buf_ops to some non-modular
> > place (splice.c). It's a hack, yes, but it seems to be the simplest
> > fix.
>
> Umm... Not even that much of a hack, really, when you consider that it
> ends up identical to socket pipe_buf_ops (page_cache_release() and
> put_page() are the same thing, so sock_pipe_buf_release() is the same
> as generic_pipe_buf_release()). Might as well merge them (and
> take to pipe.c or splice.c)...
Okay, patch below.
Thanks,
Miklos
----
Subject: fuse: fix pipe_buf_operations
From: Miklos Szeredi <mszeredi@...e.cz>
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@...iv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
Cc: stable@...r.kernel.org
---
fs/fuse/dev.c | 22 +++++-----------------
fs/splice.c | 19 +++++++++++++++++++
include/linux/pipe_fs_i.h | 2 ++
net/core/skbuff.c | 32 +-------------------------------
4 files changed, 27 insertions(+), 48 deletions(-)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1296,22 +1296,6 @@ static ssize_t fuse_dev_read(struct kioc
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(stru
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++;
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -555,6 +555,25 @@ static const struct pipe_buf_operations
.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)
{
--- 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
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);
--- 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,
.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;
--
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