Read/write requests to devices without implemented read/write_iter
using fixed buffers causes general protection fault, which totally
hangs a machine.
io_import_fixed() initialises iov_iter with bvec, but loop_rw_iter()
accesses it as iovec, so dereferencing random address.
kmap() page by page in this case
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
v2: use kmap
P.S. this one passes all tests well
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 8119cbae4fb6..1a9f34645586 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1613,9 +1613,19 @@ 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);
@@ -1624,6 +1634,9 @@ 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;
--
2.24.0
