Re: [RFC PATCH v2 03/11] ptwrite uprobes: Add a sample module to exercise interface

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] samples/uprobe: dead code in parse_probe_args due to loop invariants
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commit 77dc8c84b5d7c061149ad9471b13f1d9dabd7049
Author: Andi Kleen <ak@kernel.org>

ptwrite uprobes: Add a sample module to exercise interface

This adds a test module and userspace target program for uprobes ptwrite.
The module can be configured via parameters to register a ptwrite uprobe at
a specified offset and emit live registers or immediates into an Intel PT
stream. It is intended strictly for testing the interface.

> diff --git a/samples/uprobe-ptwrite/uprobe_ptwrite_test.c b/samples/uprobe-ptwrite/uprobe_ptwrite_test.c
> new file mode 100644
> --- /dev/null
> +++ b/samples/uprobe-ptwrite/uprobe_ptwrite_test.c
[ ... ]
> +static int parse_probe_args(void)
> +{
> +	char *s, *p, *tok;
> +	unsigned int n = 0;
> +
> +	s = kstrdup(args, GFP_KERNEL);
> +	if (!s)
> +		return -ENOMEM;
> +
> +	p = s;
> +	while ((tok = strsep(&p, ",")) != NULL) {
> +		struct uprobe_ptwrite_arg *a;
[ ... ]
> +		if (tok[0] == 'r') {
[ ... ]
> +		} else if (tok[0] == 'i') {
[ ... ]
> +		} else {
> +			pr_err("bad arg '%s'\n", tok);
> +			goto err;
> +		}
> +		n++;
> +	}
> +	if (!n) {
> +		pr_err("need 1..%d args\n", UPROBE_PTWRITE_MAX_ARGS);
> +		goto err;
> +	}

[Severity: Low]
Is this zero-argument check reachable? 

Because p is initialized to a non-NULL string returned by kstrdup(), the 
strsep() loop will always execute at least once. Inside the loop, any
invalid token triggers a goto err, skipping this check entirely. If the
token is valid, n is incremented.

Normal termination of the loop seems to guarantee that n >= 1, making this
condition structurally dead code.

> +	desc.nargs = n;
> +	kfree(s);
> +	return 0;
> +err:
> +	kfree(s);
> +	return -EINVAL;
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260917230127.924985-2-ak@kernel.org?part=3