Re: [RFC PATCH v2 05/13] mm/kwatch: add watch expression parser and dereference engine

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The watch expression parser incorrectly shadows valid 4-character symbol names starting with 'arg' (e.g., 'args', 'argv', 'argc', 'arg0').
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--- Patch [5]: [RFC PATCH v2 05/13] mm/kwatch: add watch expression parser and dereference engine ---
commit f73ceb00166a670b40222eb3b2e46fa6d5931306
Author: Jinchao Wang <wangjinchao600@gmail.com>

mm/kwatch: add watch expression parser and dereference engine

This commit introduces the watch expression parser and dereference engine for
KWatch. It allows parsing textual expressions into configurations and resolving
them safely against pt_regs at probe time.

> diff --git a/mm/kwatch/deref.c b/mm/kwatch/deref.c
> new file mode 100644
> index 0000000000000..a93c76139e7cd
> --- /dev/null
> +++ b/mm/kwatch/deref.c
[ ... ]
> +int kwatch_deref_parse(struct kwatch_config *cfg, const char *watch_expr)
> +{
[ ... ]
> +	if (!strcmp(dup_expr, "stack")) {
> +		cfg->base = KWATCH_BASE_STACK;
> +	} else if (!strncmp(dup_expr, "arg", 3) && strlen(dup_expr) == 4) {
> +		int arg_num;
> +
> +		if (kstrtoint(dup_expr + 3, 10, &arg_num) || arg_num < 1 ||
> +		    arg_num > 6) {
> +			ret = -EINVAL;
> +			goto out;
> +		}

[Severity: Medium]
Will this logic incorrectly reject valid 4-character symbol names that start
with "arg" (like "args", "argv", or "arg0")?

If a user attempts to watch a global symbol like "argv", this block intercepts
it because it starts with "arg" and is 4 characters long. However, the call to
kstrtoint() will fail on the "v" character, causing the parser to return
-EINVAL immediately instead of falling through to the general symbol lookup
block.

> +		cfg->base = KWATCH_BASE_ARG1 + (arg_num - 1);
> +	} else if (kstrtoul(dup_expr, 0, &cfg->sym_addr) == 0) {
> +		cfg->base = KWATCH_BASE_ABS_ADDR;
> +	} else {

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Sashiko AI review · https://sashiko.dev/#/patchset/20260717125023.1895892-1-wangjinchao600@gmail.com?part=5