From aa572ac16e455f177357ea57d3ad3d6fd0d96cf9 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Sun, 24 Nov 2019 11:58:24 +0300 Subject: [PATCH 1050/2944] io_uring: fix dead-hung for non-iter fixed rw to #26323578 commit 311ae9e159d81a1ec1cf645daf40b39ae5a0bd84 upstream. Read/write requests to devices without implemented read/write_iter using fixed buffers can cause general protection fault, which totally hangs a machine. io_import_fixed() initialises iov_iter with bvec, but loop_rw_iter() accesses it as iovec, dereferencing random address. kmap() page by page in this case Cc: stable@vger.kernel.org Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe Signed-off-by: Joseph Qi Acked-by: Xiaoguang Wang --- fs/io_uring.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index a5187bf..e20f42f 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1620,9 +1620,19 @@ static ssize_t loop_rw_iter(int rw, struct file *file, struct kiocb *kiocb, return -EAGAIN; while (iov_iter_count(iter)) { - struct iovec iovec = iov_iter_iovec(iter); + struct iovec iovec; ssize_t nr; + if (!iov_iter_is_bvec(iter)) { + iovec = iov_iter_iovec(iter); + } else { + /* fixed buffers import bvec */ + iovec.iov_base = kmap(iter->bvec->bv_page) + + iter->iov_offset; + iovec.iov_len = min(iter->count, + iter->bvec->bv_len - iter->iov_offset); + } + if (rw == READ) { nr = file->f_op->read(file, iovec.iov_base, iovec.iov_len, &kiocb->ki_pos); @@ -1631,6 +1641,9 @@ static ssize_t loop_rw_iter(int rw, struct file *file, struct kiocb *kiocb, iovec.iov_len, &kiocb->ki_pos); } + if (iov_iter_is_bvec(iter)) + kunmap(iter->bvec->bv_page); + if (nr < 0) { if (!ret) ret = nr; -- 1.8.3.1