librbd: clear ctx before initiating close in Image::{aio_,}close()

Image::aio_close() must clear ctx before initiating close.  Otherwise
the provided callback may see a non-NULL ctx and attempt to close the
image again from Image destructor, leading to an invalid memory access
as ImageCtx and ImageState are both freed immediately after the image
is closed (i.e. before AioCompletion is completed and the callback is
executed).

The same adjustment is made to Image::close() just for consistency.

Fixes: https://tracker.ceph.com/issues/69619
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/src/librbd/librbd.cc b/src/librbd/librbd.cc
index 49a774fdf7cb6043194945487e7c0aab2fa092ea..01bbb6e34b1b9693b8f6eceac555ceda07a1861b 100644 (file)
--- a/src/librbd/librbd.cc
+++ b/src/librbd/librbd.cc
@@ -1704,8 +1704,8 @@ namespace librbd {
       ImageCtx *ictx = (ImageCtx *)ctx;
       tracepoint(librbd, close_image_enter, ictx, ictx->name.c_str(), ictx->id.c_str());
 
+      ctx = NULL;  // before initiating close
       r = ictx->state->close();
-      ctx = NULL;
 
       tracepoint(librbd, close_image_exit, r);
     }
@@ -1721,9 +1721,9 @@ namespace librbd {
     ImageCtx *ictx = (ImageCtx *)ctx;
     tracepoint(librbd, aio_close_image_enter, ictx, ictx->name.c_str(), ictx->id.c_str(), c->pc);
 
+    ctx = NULL;  // before initiating close
     ictx->state->close(new C_AioCompletion(ictx, librbd::io::AIO_TYPE_CLOSE,
                                            get_aio_completion(c)));
-    ctx = NULL;
 
     tracepoint(librbd, aio_close_image_exit, 0);
     return 0;