mtd: docg3: fix use-after-free in docg3_release()

In docg3_release(), the docg3 pointer is obtained from
cascade->floors[0]->priv before the loop that calls
doc_release_device() on each floor. doc_release_device() frees the
docg3 struct via kfree(docg3) at line 1881. After the loop,
docg3->cascade->bch dereferences the already-freed pointer.

Fix this by accessing cascade->bch directly, which is equivalent
since docg3->cascade points back to the same cascade struct, and
is already available as a local variable. This also removes the
now-unused docg3 local variable.

Fixes: c8ae3f744ddc ("lib/bch: Rework a little bit the exported function names")
Cc: stable@vger.kernel.org
Signed-off-by: James Kim <james010kim@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

diff --git a/drivers/mtd/devices/docg3.c b/drivers/mtd/devices/docg3.c
index 33050a2a80f79e31d84f6c6d4068d798c930c2a0..603fd0efc2ea2da3f7f2e739a7a3c6f1fd346155 100644 (file)
--- a/drivers/mtd/devices/docg3.c
+++ b/drivers/mtd/devices/docg3.c
@@ -2049,7 +2049,6 @@ err_probe:
 static void docg3_release(struct platform_device *pdev)
 {
        struct docg3_cascade *cascade = platform_get_drvdata(pdev);
-       struct docg3 *docg3 = cascade->floors[0]->priv;
        int floor;
 
        doc_unregister_sysfs(pdev, cascade);
@@ -2057,7 +2056,7 @@ static void docg3_release(struct platform_device *pdev)
                if (cascade->floors[floor])
                        doc_release_device(cascade->floors[floor]);
 
-       bch_free(docg3->cascade->bch);
+       bch_free(cascade->bch);
 }
 
 #ifdef CONFIG_OF