Commit dc0f7c58 authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman

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

commit 6ae08069 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 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);
	}
Signed-off-by: default avatarEric Biggers <ebiggers3@gmail.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d5c7bab6
...@@ -366,18 +366,17 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) ...@@ -366,18 +366,17 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
int offset = buf->offset + buf->len; int offset = buf->offset + buf->len;
if (ops->can_merge && offset + chars <= PAGE_SIZE) { if (ops->can_merge && offset + chars <= PAGE_SIZE) {
int error = ops->confirm(pipe, buf); ret = ops->confirm(pipe, buf);
if (error) if (ret)
goto out; goto out;
ret = copy_page_from_iter(buf->page, offset, chars, from); ret = copy_page_from_iter(buf->page, offset, chars, from);
if (unlikely(ret < chars)) { if (unlikely(ret < chars)) {
error = -EFAULT; ret = -EFAULT;
goto out; goto out;
} }
do_wakeup = 1; do_wakeup = 1;
buf->len += chars; buf->len += ret;
ret = chars;
if (!iov_iter_count(from)) if (!iov_iter_count(from))
goto out; goto out;
} }
......
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