From dc0f7c58ecaff61e587153a0a6bc4884846f1e8b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sat, 17 Oct 2015 16:26:09 -0500 Subject: [PATCH] fs/pipe.c: return error code rather than 0 in pipe_write() 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 #include #include 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 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/pipe.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 8865f79637007..14788ddcd3f3b 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -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; } -- 2.47.2