This is a note to let you know that I've just added the patch titled mtd: mtdconcat: Check _read, _write callbacks existence before assignment to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mtd-mtdconcat-check-_read-_write-callbacks-existence.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 7b346db2954bc65af7bb30cb79369ded3eae2013 Author: Zhihao Cheng <chengzhihao1@xxxxxxxxxx> Date: Tue Aug 17 19:48:57 2021 +0800 mtd: mtdconcat: Check _read, _write callbacks existence before assignment [ Upstream commit a89d69a44e282be95ae76125dddc79515541efeb ] Since 2431c4f5b46c3 ("mtd: Implement mtd_{read,write}() as wrappers around mtd_{read,write}_oob()") don't allow _write|_read and _write_oob|_read_oob existing at the same time, we should check the existence of callbacks "_read and _write" from subdev's master device (We can trust master device since it has been registered) before assigning, otherwise following warning occurs while making concatenated device: WARNING: CPU: 2 PID: 6728 at drivers/mtd/mtdcore.c:595 add_mtd_device+0x7f/0x7b0 Fixes: 2431c4f5b46c3 ("mtd: Implement mtd_{read,write}() around ...") Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx> Link: https://lore.kernel.org/linux-mtd/20210817114857.2784825-3-chengzhihao1@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c index af51eee6b5e8..f685a581df48 100644 --- a/drivers/mtd/mtdconcat.c +++ b/drivers/mtd/mtdconcat.c @@ -694,6 +694,10 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c concat->mtd._block_markbad = concat_block_markbad; if (subdev_master->_panic_write) concat->mtd._panic_write = concat_panic_write; + if (subdev_master->_read) + concat->mtd._read = concat_read; + if (subdev_master->_write) + concat->mtd._write = concat_write; concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks; @@ -755,8 +759,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *subdev[], /* subdevices to c concat->mtd.name = name; concat->mtd._erase = concat_erase; - concat->mtd._read = concat_read; - concat->mtd._write = concat_write; concat->mtd._sync = concat_sync; concat->mtd._lock = concat_lock; concat->mtd._unlock = concat_unlock;