2023-09-19 16:44:47

by Shivamurthy Shastri

Subject: [PATCH] mtd: map_ram: prevent use of point and unpoint when NO_XIP is set

When the DT property no-unaligned-direct-access is set, map->phys is set
to NO_XIP. With this property set, the flash should not be exposed
directly to MTD users, since it cannot be mapped.

map_ram() exposes the flash direct access unconditionally which leads to
access errors (when the bus width does not match the RAM width).

Therefore do not set point and unpoint when NO_XIP is set.

Signed-off-by: Shivamurthy Shastri <[email protected]>
Reviewed-by: Benedikt Spranger <[email protected]>
---
drivers/mtd/chips/map_ram.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/chips/map_ram.c b/drivers/mtd/chips/map_ram.c
index e8dd6496927e..f9d3e32ef8e9 100644
--- a/drivers/mtd/chips/map_ram.c
+++ b/drivers/mtd/chips/map_ram.c
@@ -70,12 +70,16 @@ static struct mtd_info *map_ram_probe(struct map_info *map)
mtd->_read = mapram_read;
mtd->_write = mapram_write;
mtd->_panic_write = mapram_write;
- mtd->_point = mapram_point;
mtd->_sync = mapram_nop;
- mtd->_unpoint = mapram_unpoint;
mtd->flags = MTD_CAP_RAM;
mtd->writesize = 1;

+ /* Disable direct access when NO_XIP is set */
+ if (map->phys != NO_XIP) {
+ mtd->_point = mapram_point;
+ mtd->_unpoint = mapram_unpoint;
+ }
+
mtd->erasesize = PAGE_SIZE;
while(mtd->size & (mtd->erasesize - 1))
mtd->erasesize >>= 1;
--
2.34.1

2023-09-22 18:44:31

by Miquel Raynal

Subject: Re: [PATCH] mtd: map_ram: prevent use of point and unpoint when NO_XIP is set

On Tue, 2023-09-19 at 11:33:20 UTC, Shivamurthy Shastri wrote:
> When the DT property no-unaligned-direct-access is set, map->phys is set
> to NO_XIP. With this property set, the flash should not be exposed
> directly to MTD users, since it cannot be mapped.
>
> map_ram() exposes the flash direct access unconditionally which leads to
> access errors (when the bus width does not match the RAM width).
>
> Therefore do not set point and unpoint when NO_XIP is set.
>
> Signed-off-by: Shivamurthy Shastri <[email protected]>
> Reviewed-by: Benedikt Spranger <[email protected]>

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

Miquel