Re: [PATCH 3/3] cxl/hdm: Restore commit_end when decoder enumeration fails

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Transient reset of `port->commit_end` allows concurrent bypass of safety checks in `cxl_mem_sanitize`, potentially destroying active memory.
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--- Patch [3]: [PATCH 3/3] cxl/hdm: Restore commit_end when decoder enumeration fails ---
commit 0d7f87c9ca0ba7b9bbdd31e5ea90994445b1c9b5
Author: Alison Schofield <[email protected]>

cxl/hdm: Restore commit_end when decoder enumeration fails

This commit resets port->commit_end to -1 before enumerating decoders so
the commit state is rebuilt from the decoders actually committed on each
probe. This prevents previous enumeration failures from causing subsequent
probes to fail.

> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 75d17120233da..0145d3db31070 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -1178,6 +1178,10 @@ static int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm,
>  
>  	cxl_settle_decoders(cxlhdm);
>  
> +	/* Reset to the none committed baseline for a fresh enumeration */
> +	scoped_guard(rwsem_write, &cxl_rwsem.region)
> +		port->commit_end = -1;

[Severity: High]
Does this scoped_guard drop the lock too early?

Because scoped_guard only holds the lock for the following single statement,
the rwsem_write lock is released immediately after setting port->commit_end
to -1. This leaves the transient -1 state exposed to readers without protection
while the loop below performs the hardware enumeration.

Could a concurrent reader like cxl_mem_sanitize() acquire the read lock
during this window, observe a temporarily empty committed decoder count
(since cxl_num_decoders_committed() evaluates the exposed -1), and 
erroneously bypass its safety checks to securely erase actively mapped memory?

> +
>  	for (i = 0; i < cxlhdm->decoder_count; i++) {
>  		int rc, target_count = cxlhdm->target_count;
>  		struct cxl_decoder *cxld;

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3