Commit 6ae08069 authored by Eric Biggers's avatar Eric Biggers Committed by Al Viro

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

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 f0d1bec9 ("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);
	}

Cc: stable@vger.kernel.org # at least v3.15+
Signed-off-by: default avatarEric Biggers <ebiggers3@gmail.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent e9bb1f9b
......@@ -366,18 +366,17 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
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;
}
......
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