Re: [PATCH 26/79] block: rnull: add badblocks support

[Alice Ryhl]

On Mon, Feb 16, 2026 at 12:35:13AM +0100, Andreas Hindborg wrote:
> Add badblocks support to the rnull driver with a configfs interface for
> managing bad sectors.
> 
> - Configfs attribute for adding/removing bad blocks via "+start-end" and
>   "-start-end" syntax.
> - Request handling that checks for bad blocks and returns IO errors.
> - Updated request completion to handle error status properly.
> 
> The badblocks functionality is disabled by default and is enabled when
> first bad block is added.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>

> +    fn store(this: &DeviceConfig, page: &[u8]) -> Result {
> +        // This attribute can be set while device is powered.
> +
> +        for line in core::str::from_utf8(page)?.lines() {
> +            let mut chars = line.chars();
> +            match chars.next() {
> +                Some(sign @ '+' | sign @ '-') => {
> +                    if let Some((start, end)) = chars.as_str().split_once('-') {
> +                        let start: u64 = start.parse().map_err(|_| EINVAL)?;
> +                        let end: u64 = end.parse().map_err(|_| EINVAL)?;
> +
> +                        if start > end {
> +                            return Err(EINVAL);
> +                        }
> +
> +                        this.data.lock().bad_blocks.enable();
> +
> +                        if sign == '+' {
> +                            this.data.lock().bad_blocks.set_bad(start..=end, true)?;
> +                        } else {
> +                            this.data.lock().bad_blocks.set_good(start..=end)?;

Taking lock twice: TOCTOU.

> @@ -118,6 +125,7 @@ fn make_group(
>                      home_node: bindings::NUMA_NO_NODE,
>                      discard: false,
>                      no_sched: false,
> +                    bad_blocks: Arc::pin_init(BadBlocks::new(false), GFP_KERNEL)?,
>                  }),
>              }),
>              core::iter::empty(),

[..]

> @@ -155,6 +160,7 @@ fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
>                      home_node: *module_parameters::home_node.value(),
>                      discard: *module_parameters::discard.value() != 0,
>                      no_sched: *module_parameters::no_sched.value() != 0,
> +                    bad_blocks: Arc::pin_init(BadBlocks::new(false), GFP_KERNEL)?,

It seems weird to construct this Arc in two places. Is it shared or not?

Alice