From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: [PATCH 2/2] fs/pipe.c: return error code rather than 0 in pipe_write() Date: Sat, 17 Oct 2015 16:26:09 -0500 Message-ID: <1445117169-9665-2-git-send-email-ebiggers3@gmail.com> References: <1445117169-9665-1-git-send-email-ebiggers3@gmail.com> Cc: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, Eric Biggers To: linux-fsdevel@vger.kernel.org Return-path: In-Reply-To: <1445117169-9665-1-git-send-email-ebiggers3@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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 --- fs/pipe.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 997de34..42cf8dd 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; } -- 2.6.1