From: Pavel Begunkov asml.silence@gmail.com
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 asml.silence@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/io_uring.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1351,9 +1351,19 @@ static ssize_t loop_rw_iter(int rw, stru 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); @@ -1362,6 +1372,9 @@ static ssize_t loop_rw_iter(int rw, stru iovec.iov_len, &kiocb->ki_pos); }
+ if (iov_iter_is_bvec(iter)) + kunmap(iter->bvec->bv_page); + if (nr < 0) { if (!ret) ret = nr;