From: Xiaoguang Wang <[email protected]>
[ Upstream commit 6f2cc1664db20676069cff27a461ccc97dbfd114 ]
In io_read() or io_write(), when io request is submitted successfully,
it'll go through the below sequence:
kfree(iovec);
req->flags &= ~REQ_F_NEED_CLEANUP;
return ret;
But clearing REQ_F_NEED_CLEANUP might be unsafe. The io request may
already have been completed, and then io_complete_rw_iopoll()
and io_complete_rw() will be called, both of which will also modify
req->flags if needed. This causes a race condition, with concurrent
non-atomic modification of req->flags.
To eliminate this race, in io_read() or io_write(), if io request is
submitted successfully, we don't remove REQ_F_NEED_CLEANUP flag. If
REQ_F_NEED_CLEANUP is set, we'll leave __io_req_aux_free() to the
iovec cleanup work correspondingly.
Cc: [email protected]
Signed-off-by: Xiaoguang Wang <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/io_uring.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2614,8 +2614,8 @@ copy_iov:
}
}
out_free:
- kfree(iovec);
- req->flags &= ~REQ_F_NEED_CLEANUP;
+ if (!(req->flags & REQ_F_NEED_CLEANUP))
+ kfree(iovec);
return ret;
}
@@ -2737,8 +2737,8 @@ copy_iov:
}
}
out_free:
- req->flags &= ~REQ_F_NEED_CLEANUP;
- kfree(iovec);
+ if (!(req->flags & REQ_F_NEED_CLEANUP))
+ kfree(iovec);
return ret;
}
