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Received: from sslproxy01.your-server.de ([78.46.139.224]) by www62.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1tNt4a-0003N0-G3; Wed, 18 Dec 2024 13:22:40 +0100 Received: from [81.6.34.132] (helo=[192.168.3.135]) by sslproxy01.your-server.de with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1tNt4Z-00075R-24; Wed, 18 Dec 2024 13:22:39 +0100 Message-ID: <3ec9783f-0331-41bb-9f02-6d35cb25e197@iogearbox.net> Date: Wed, 18 Dec 2024 13:22:37 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] bpf: Fix bpf_get_smp_processor_id() on !CONFIG_SMP To: Andrea Righi , Alexei Starovoitov Cc: John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Andrii Nakryiko References: <20241217195813.622568-1-arighi@nvidia.com> Content-Language: en-US From: Daniel Borkmann Autocrypt: addr=daniel@iogearbox.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 1.0.7/27491/Wed Dec 18 10:43:25 2024) On 12/17/24 8:58 PM, Andrea Righi wrote: > On x86-64 calling bpf_get_smp_processor_id() in a kernel with CONFIG_SMP > disabled can trigger the following bug, as pcpu_hot is unavailable: > > [ 8.471774] BUG: unable to handle page fault for address: 00000000936a290c > [ 8.471849] #PF: supervisor read access in kernel mode > [ 8.471881] #PF: error_code(0x0000) - not-present page > > Fix by inlining a return 0 in the !CONFIG_SMP case. > > Fixes: 1ae6921009e5 ("bpf: inline bpf_get_smp_processor_id() helper") > Cc: Daniel Borkmann > Cc: Andrii Nakryiko > Signed-off-by: Andrea Righi Acked-by: Daniel Borkmann