Re: [PATCH v7 20/29] dyndbg: refactor param_set_dyndbg_classes and below

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The refactored `param_set_dyndbg_module_classes` is structurally incapable of correctly applying existing global classmap settings to newly loaded modules, and it corrupts the global state.
--

--- Patch [20]: [PATCH v7 20/29] dyndbg: refactor param_set_dyndbg_classes and below ---
commit fd7e6888285afde6b911cef67e7e2452e7180dba
Author: Jim Cromie <jim.cromie@gmail.com>

dyndbg: refactor param_set_dyndbg_classes and below

This commit refactors the param_set_dyndbg_classes callchain to support
module-specific classmap updates, primarily intended for modprobe handling.
It splits the function into upper and lower parts, threading a modname
parameter through to ddebug_exec_queries. It also adds a check in
ddebug_apply_class_bitmap to skip printing if bits haven't changed.

> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index f66e5373e61e2..a619cefd801f7 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
[ ... ]
> @@ -625,7 +626,9 @@ static int ddebug_apply_class_bitmap(const struct ddebug_class_param *dcp,
>  	int matches = 0;
>  	int bi, ct;
>  
> -	v2pr_info("apply: 0x%lx to: 0x%lx\n", *new_bits, *old_bits);
> +	if (*new_bits != *old_bits)
> +		v2pr_info("apply bitmap: 0x%lx to: 0x%lx for %s\n", *new_bits,
> +			  *old_bits, query_modname ?: "'*'");
>  
>  	for (bi = 0; bi < map->length; bi++) {
>  		if (test_bit(bi, new_bits) == test_bit(bi, old_bits))
>  			continue;

[Severity: Medium]
When applying the current global state to a newly probed module, will this
continue statement incorrectly skip all configuration queries?

Since old_bits represents the global state, test_bit() will evaluate to true
when applying the same global configuration to a new module, silently
skipping required query updates.

>  		snprintf(query, QUERY_SIZE, "class %s %c%s", map->class_names[bi],
>  			 test_bit(bi, new_bits) ? '+' : '-', dcp->flags);
>  
[ ... ]
> @@ -683,8 +693,8 @@ int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
>  				KP_NAME(kp), inrep, CLASSMAP_BITMASK(map->length));
>  			inrep &= CLASSMAP_BITMASK(map->length);
>  		}
> -		v2pr_info("bits:%lx > %s\n", inrep, KP_NAME(kp));
> -		totct += ddebug_apply_class_bitmap(dcp, &inrep, dcp->bits);
> +		v2pr_info("bits:0x%lx > %s.%s\n", inrep, mod_name ?: "*", KP_NAME(kp));
> +		totct += ddebug_apply_class_bitmap(dcp, &inrep, dcp->bits, mod_name);
>  		*dcp->bits = inrep;

[Severity: Medium]
Does this code inadvertently corrupt the global state if a module-specific
override is applied?

It appears that *dcp->bits (the global parameter state) is unconditionally
overwritten with inrep, even when a mod_name is provided.

Should the state update be conditional on mod_name being NULL, to prevent
modprobe handling from modifying the global state?

>  		break;
>  	case DD_CLASS_TYPE_LEVEL_NUM:
> @@ -697,7 +707,7 @@ int param_set_dyndbg_classes(const char *instr, const struct kernel_param *kp)
>  		old_bits = CLASSMAP_BITMASK(*dcp->lvl);
>  		new_bits = CLASSMAP_BITMASK(inrep);
>  		v2pr_info("lvl:%ld bits:0x%lx > %s\n", inrep, new_bits, KP_NAME(kp));
> -		totct += ddebug_apply_class_bitmap(dcp, &new_bits, &old_bits);
> +		totct += ddebug_apply_class_bitmap(dcp, &new_bits, &old_bits, mod_name);
>  		*dcp->lvl = inrep;

[Severity: Medium]
Similarly, is the global *dcp->lvl state unconditionally overwritten here
when a module-specific override is applied for LEVEL_NUM map types?

>  		break;
>  	default:

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260721-dd-maint-2-v7-0-010fbe73b311@gmail.com?part=20