linux-kernel - [PATCH v3 3/3] ubi: ubi_create_volume: Fix use-after-free when volume creation failed

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Date:   Tue, 10 May 2022 20:31:26 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <richard@....at>, <miquel.raynal@...tlin.com>, <vigneshr@...com>,
        <mcoquelin.stm32@...il.com>, <kirill.shutemov@...ux.intel.com>,
        <s.hauer@...gutronix.de>, <gregkh@...uxfoundation.org>,
        <arne.edholm@...s.com>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <chengzhihao1@...wei.com>, <yukuai3@...wei.com>
Subject: [PATCH v3 3/3] ubi: ubi_create_volume: Fix use-after-free when volume creation failed

There is an use-after-free problem for 'eba_tbl' in ubi_create_volume()'s
error handling path:

  ubi_eba_replace_table(vol, eba_tbl)
    vol->eba_tbl = tbl
out_mapping:
  ubi_eba_destroy_table(eba_tbl)   // Free 'eba_tbl'
out_unlock:
  put_device(&vol->dev)
    vol_release
      kfree(tbl->entries)	  // UAF

Fix it by removing redundant 'eba_tbl' releasing.
Fetch a reproducer in [Link].

Fixes: 493cfaeaa0c9b ("mtd: utilize new cdev_device_add helper function")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215965
Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
---
 drivers/mtd/ubi/vmt.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 1bc7b3a05604..6ea95ade4ca6 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -309,7 +309,6 @@ int ubi_create_volume(struct ubi_device *ubi, struct ubi_mkvol_req *req)
 	ubi->volumes[vol_id] = NULL;
 	ubi->vol_count -= 1;
 	spin_unlock(&ubi->volumes_lock);
-	ubi_eba_destroy_table(eba_tbl);
 out_acc:
 	spin_lock(&ubi->volumes_lock);
 	ubi->rsvd_pebs -= vol->reserved_pebs;
-- 
2.31.1