[PATCH] mtd: fix 'part' field data corruption in mtd_info

[PATCH] mtd: fix 'part' field data corruption in mtd_info

[Oleksandr Ocheretnyi]

Commit 46b5889cc2c5 ("mtd: implement proper partition handling")
started using "mtd_get_master_ofs()" in mtd callbacks to determine
memory offsets by means of 'part' field from mtd_info, what previously
was smashed accessing 'master' field in the mtd_set_dev_defaults() method.
That provides wrong offset what causes hardware access errors.

Just make 'part', 'master' as separate fields, rather than using
union type to avoid 'part' data corruption when mtd_set_dev_defaults()
is called.

Fixes: 46b5889cc2c5 ("mtd: implement proper partition handling")
Signed-off-by: Oleksandr Ocheretnyi <oocheret@cisco.com>
---
 include/linux/mtd/mtd.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 88227044fc86..8a2c60235ebb 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -394,10 +394,8 @@ struct mtd_info {
 	/* List of partitions attached to this MTD device */
 	struct list_head partitions;
 
-	union {
-		struct mtd_part part;
-		struct mtd_master master;
-	};
+	struct mtd_part part;
+	struct mtd_master master;
 };
 
 static inline struct mtd_info *mtd_get_master(struct mtd_info *mtd)
-- 
2.26.2.Cisco

Re: [PATCH] mtd: fix 'part' field data corruption in mtd_info

[Miquel Raynal]

On Sun, 2022-04-17 at 18:46:47 UTC, Oleksandr Ocheretnyi wrote:
> Commit 46b5889cc2c5 ("mtd: implement proper partition handling")
> started using "mtd_get_master_ofs()" in mtd callbacks to determine
> memory offsets by means of 'part' field from mtd_info, what previously
> was smashed accessing 'master' field in the mtd_set_dev_defaults() method.
> That provides wrong offset what causes hardware access errors.
> 
> Just make 'part', 'master' as separate fields, rather than using
> union type to avoid 'part' data corruption when mtd_set_dev_defaults()
> is called.
> 
> Fixes: 46b5889cc2c5 ("mtd: implement proper partition handling")
> Signed-off-by: Oleksandr Ocheretnyi <oocheret@cisco.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/fixes, thanks.

Miquel