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Wed, 27 Nov 2024 08:02:17 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 27 Nov 2024 09:02:07 +0100 (CET) Date: Wed, 27 Nov 2024 09:01:56 +0100 From: Oleg Nesterov To: Jann Horn Cc: Andrii Nakryiko , 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 Message-ID: <20241127080133.GA7717@redhat.com> References: <20241122035922.3321100-1-andrii@kernel.org> <20241122035922.3321100-2-andrii@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Rspamd-Queue-Id: 4F7021C0004 X-Stat-Signature: qwygywz9cr6ot5deqeueaos877sdx4gb X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1732694555-458875 X-HE-Meta: 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 QBS4NsOQ s61D0/0FK92AEwhf0gex9thDS1alv+kjmmUwX/DrHBre81oQq4IyK4A0kM+WYyEhNB540D4EPAPIDL5Hwd0439T8tV6Myn4XFIW7rm9uIx6mKgkpIpo4AqZzX1y744BH45wSaubJulzLJnqVvVv2u82AyD8/hkSssxfWjHKFbadqY2UhqVt2BfeoaYqJUUADsUTuvtgsSw8jyproeE/ICRMttys2eUeJyUOwhGSl+NQ8hJ6ao+CNdcndGw8PMj6Aar8DkwG2CFgnrbXPQEbknMxBIGhQs6e7Dwsct2ojX0bkncZ07P8sq4AVOmwfbT/M6Nt+mZC9OtG3jNWW4XwafdqRU4iv0ytB2XXq9szZY8fWRjCZkH6uCxlLM0DmchNfUvYoHfiGe047K20E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/26, Jann Horn wrote: > > On Fri, Nov 22, 2024 at 4:59 AM Andrii Nakryiko 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.