recompress_store() parses the type= parameter with three if statements
checking for "idle", "huge", and "huge_idle". An unrecognized value
silently falls through with mode left at 0, causing the recompression
pass to run with no slot filter — processing all slots instead of the
intended subset.

Add a !mode check after the type parsing block to return -EINVAL for
unrecognized values, consistent with the function's other parameter
validation.

Suggested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
---

Changes in v2:
  - Use !mode check after the strcmp chain instead of restructuring
    into if/else if/else, as suggested by Sergey Senozhatsky.

 drivers/block/zram/zram_drv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 8ea2a12..67dea80 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2552,6 +2552,9 @@ static ssize_t recompress_store(struct device *dev,
 			if (!strcmp(val, "huge_idle"))
 				mode = RECOMPRESS_IDLE | RECOMPRESS_HUGE;

+			if (!mode)
+				return -EINVAL;
+
 			continue;
 		}

--
2.34.1

Adding Andrew on this:
Message-ID: <20260407153027.42425-1-astellman@stellman-greene.com>


On (26/04/07 11:30), Andrew Stellman wrote:
[..]
> recompress_store() parses the type= parameter with three if statements
> checking for "idle", "huge", and "huge_idle". An unrecognized value
> silently falls through with mode left at 0, causing the recompression
> pass to run with no slot filter — processing all slots instead of the
> intended subset.
> 
> Add a !mode check after the type parsing block to return -EINVAL for
> unrecognized values, consistent with the function's other parameter
> validation.
> 
> Suggested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
> ---

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

Thank you.