Re: [PATCH bpf-next] selftests/bpf: add test for arena vma split and fork rejection

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Multi-line comments do not follow the BPF subsystem style guide.
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commit 68912cf41a7e5ee9f6445ed2bc4cecbbb14bad14
Author: Ruslan Valiyev <linuxoid@gmail.com>

selftests/bpf: add test for arena vma split and fork rejection

This commit adds a selftest to verify that an arena map's mmap()ed VMA
cannot be split with a partial munmap() or inherited across fork().

> diff --git a/tools/testing/selftests/bpf/prog_tests/arena_fork.c b/tools/testing/selftests/bpf/prog_tests/arena_fork.c
> new file mode 100644
> index 0000000000000..f3d5218c9e071
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/arena_fork.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <errno.h>
> +#include <sys/mman.h>
> +#include <sys/wait.h>
> +
> +/* Regression test for commit 4fddde2a732d ("bpf: Fix use-after-free in
> + * arena_vm_close on fork"): an arena VMA must reject a splitting munmap()
> + * (.may_split) and must not be inherited across fork() (VM_DONTCOPY). On
> + * an unfixed kernel both operations succeed.
> + */

[Severity: Low]
This isn't a bug, but does this multi-line comment format follow the BPF
subsystem style? The subsystem guidelines state that multi-line comments
should have the opening /* on its own line.

[ ... ]

> +	/* A split of the arena VMA must be rejected (.may_split). */
> +	ret = munmap((char *)area + ps, ps);
> +	err = errno;
> +	ASSERT_ERR(ret, "split munmap rejected");
> +	ASSERT_EQ(err, EINVAL, "split munmap errno");
> +
> +	/* The child of a fork() must not inherit the arena VMA (VM_DONTCOPY);
> +	 * mincore() returns ENOMEM for the unmapped range.
> +	 */

[Severity: Low]
This isn't a bug, but does this comment also need the opening /* on its own
line to match the preferred BPF multi-line comment style?

[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260603094428.2597058-1-linuxoid@gmail.com?part=1