From: Shakeel Butt <shakeel.butt@linux.dev>
To: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>,
Puranjay Mohan <puranjay@kernel.org>,
Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH bpf v4 2/3] bpf: Avoid faultable build ID reads under mm locks
Date: Thu, 14 May 2026 13:47:42 -0700 [thread overview]
Message-ID: <agYzuDIJszA_7rp3@linux.dev> (raw)
In-Reply-To: <20260514184727.1067141-3-ihor.solodrai@linux.dev>
On Thu, May 14, 2026 at 11:47:26AM -0700, Ihor Solodrai wrote:
> Sleepable build ID parsing can block in __kernel_read() [1], so the
> stackmap sleepable path must not call it while holding mmap_lock or a
> per-VMA read lock.
>
> The issue and the fix are conceptually similar to a recent procfs
> patch [2].
>
> Resolve each covered VMA with a stable read-side reference, preferring
> lock_vma_under_rcu() and falling back to mmap_read_trylock()
Why trylock()? Why not just reuse the mechanism introduced in [2]? That is
abstract out the mechanism introduced in [2] in mm core and reuse it.
> only long
> enough to acquire the VMA read lock. Take a reference to the backing
> file, drop the VMA lock, and then parse the build ID through
> (sleepable) build_id_parse_file().
>
> [1]: https://lore.kernel.org/all/20251218005818.614819-1-shakeel.butt@linux.dev/
> [2]: https://lore.kernel.org/all/20260128183232.2854138-1-andrii@kernel.org/
>
next prev parent reply other threads:[~2026-05-14 20:48 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-14 18:47 [PATCH bpf v4 0/3] bpf: Implement stack_map_get_build_id_offset_sleepable() Ihor Solodrai
2026-05-14 18:47 ` [PATCH bpf v4 1/3] bpf: Factor out stack_map_build_id_set_ip() in stackmap.c Ihor Solodrai
2026-05-14 18:47 ` [PATCH bpf v4 2/3] bpf: Avoid faultable build ID reads under mm locks Ihor Solodrai
2026-05-14 19:37 ` bot+bpf-ci
2026-05-14 20:37 ` Ihor Solodrai
2026-05-14 20:47 ` Shakeel Butt [this message]
2026-05-14 21:31 ` Ihor Solodrai
2026-05-14 22:14 ` Shakeel Butt
2026-05-14 22:49 ` Ihor Solodrai
2026-05-14 23:02 ` Shakeel Butt
2026-05-14 18:47 ` [PATCH bpf v4 3/3] bpf: Cache build IDs in sleepable stackmap path Ihor Solodrai
2026-05-14 19:37 ` bot+bpf-ci
2026-05-15 0:24 ` Alexei Starovoitov
2026-05-15 0:27 ` Ihor Solodrai
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