Patch "fs/pipe.c: return error code rather than 0 in pipe_write()" has been added to the 4.3-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    fs/pipe.c: return error code rather than 0 in pipe_write()

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-pipe.c-return-error-code-rather-than-0-in-pipe_write.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6ae08069939f17422835448acae76bda8d96b16a Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 17 Oct 2015 16:26:09 -0500
Subject: fs/pipe.c: return error code rather than 0 in pipe_write()

From: Eric Biggers <ebiggers3@gmail.com>

commit 6ae08069939f17422835448acae76bda8d96b16a upstream.

pipe_write() would return 0 if it failed to merge the beginning of the
data to write with the last, partially filled pipe buffer.  It should
return an error code instead.  Userspace programs could be confused by
write() returning 0 when called with a nonzero 'count'.

The EFAULT error case was a regression from f0d1bec9d5 ("new helper:
copy_page_from_iter()"), while the ops->confirm() error case was a much
older bug.

Test program:

	#include <assert.h>
	#include <errno.h>
	#include <unistd.h>

	int main(void)
	{
		int fd[2];
		char data[1] = {0};

		assert(0 == pipe(fd));
		assert(1 == write(fd[1], data, 1));

		/* prior to this patch, write() returned 0 here  */
		assert(-1 == write(fd[1], NULL, 1));
		assert(errno == EFAULT);
	}

Signed-off-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/pipe.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -366,18 +366,17 @@ pipe_write(struct kiocb *iocb, struct io
 		int offset = buf->offset + buf->len;
 
 		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
-			int error = ops->confirm(pipe, buf);
-			if (error)
+			ret = ops->confirm(pipe, buf);
+			if (ret)
 				goto out;
 
 			ret = copy_page_from_iter(buf->page, offset, chars, from);
 			if (unlikely(ret < chars)) {
-				error = -EFAULT;
+				ret = -EFAULT;
 				goto out;
 			}
 			do_wakeup = 1;
-			buf->len += chars;
-			ret = chars;
+			buf->len += ret;
 			if (!iov_iter_count(from))
 				goto out;
 		}


Patches currently in stable-queue which might be from ebiggers3@gmail.com are

queue-4.3/fs-pipe.c-return-error-code-rather-than-0-in-pipe_write.patch