From: Oleg Nesterov <oleg@redhat.com>
To: Jann Horn <jannh@google.com>
Cc: Andrii Nakryiko <andrii@kernel.org>,
linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, peterz@infradead.org,
mingo@kernel.org, torvalds@linux-foundation.org,
rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, jolsa@kernel.org,
paulmck@kernel.org, willy@infradead.org, surenb@google.com,
mjguzik@gmail.com, brauner@kernel.org, mhocko@kernel.org,
vbabka@suse.cz, shakeel.butt@linux.dev, hannes@cmpxchg.org,
lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com,
david@redhat.com, arnd@arndb.de, viro@zeniv.linux.org.uk,
hca@linux.ibm.com
Subject: Re: [PATCH v5 tip/perf/core 1/2] uprobes: simplify find_active_uprobe_rcu() VMA checks
Date: Wed, 27 Nov 2024 09:01:56 +0100 [thread overview]
Message-ID: <20241127080133.GA7717@redhat.com> (raw)
In-Reply-To: <CAG48ez06=E-rXYk59yJR2aKFD2yaqcQu+6wqVau9pQ8X36A+aQ@mail.gmail.com>
On 11/26, Jann Horn wrote:
>
> On Fri, Nov 22, 2024 at 4:59 AM Andrii Nakryiko <andrii@kernel.org> wrote:
> > At the point where find_active_uprobe_rcu() is used we know that VMA in
> > question has triggered software breakpoint, so we don't need to validate
> > vma->vm_flags. Keep only vma->vm_file NULL check.
>
> How do we know that the VMA we find triggered a software breakpoint?
> Between the time a software breakpoint was hit and the time we took
> the mmap_read_lock(), the VMA could have been replaced with an
> entirely different one, right?
Right, but this doesn't really differ from the case when another thread
replaces (or even unmaps) this VMA after find_active_uprobe_rcu() drops
mm->mmap_lock and returns a found uprobe.
So I think this is fine.
Oleg.
next prev parent reply other threads:[~2024-12-05 15:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-22 3:59 [PATCH v5 tip/perf/core 0/2] uprobes: speculative lockless VMA-to-uprobe lookup Andrii Nakryiko
2024-11-22 3:59 ` [PATCH v5 tip/perf/core 1/2] uprobes: simplify find_active_uprobe_rcu() VMA checks Andrii Nakryiko
2024-11-26 22:19 ` Jann Horn
2024-11-27 4:49 ` Andrii Nakryiko
2024-11-27 8:01 ` Oleg Nesterov [this message]
2024-11-22 3:59 ` [PATCH v5 tip/perf/core 2/2] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution Andrii Nakryiko
2024-11-22 14:56 ` Liam R. Howlett
2024-11-22 11:07 ` [PATCH v5 tip/perf/core 0/2] uprobes: speculative lockless VMA-to-uprobe lookup Peter Zijlstra
2024-11-22 15:04 ` Suren Baghdasaryan
2024-11-22 17:48 ` Suren Baghdasaryan
2024-11-23 20:35 ` Peter Zijlstra
2024-11-24 19:56 ` Suren Baghdasaryan
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