linux-kernel - [PATCH] fs: fuse: dax: set fc->dax to NULL in fuse_dax_conn

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Message-Id: <20231116075726.28634-1-hbh25y@gmail.com>
Date:   Thu, 16 Nov 2023 15:57:26 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     miklos@...redi.hu, vgoyal@...hat.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hangyu Hua <hbh25y@...il.com>
Subject: [PATCH] fs: fuse: dax: set fc->dax to NULL in fuse_dax_conn_free()

fuse_dax_conn_free() will be called when fuse_fill_super_common() fails
after fuse_dax_conn_alloc(). Then deactivate_locked_super() in
virtio_fs_get_tree() will call virtio_kill_sb() to release the discarded
superblock. This will call fuse_dax_conn_free() again in fuse_conn_put(),
resulting in a possible double free.

Fixes: 1dd539577c42 ("virtiofs: add a mount option to enable dax")
Signed-off-by: Hangyu Hua <hbh25y@...il.com>
---
 fs/fuse/dax.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 23904a6a9a96..12ef91d170bb 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -1222,6 +1222,7 @@ void fuse_dax_conn_free(struct fuse_conn *fc)
 	if (fc->dax) {
 		fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
 		kfree(fc->dax);
+		fc->dax = NULL;
 	}
 }
 
-- 
2.34.1