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Date: Mon, 7 Sep 2026 00:34:45 +0100
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Subject: Re: [PATCH v3] bpf: Fix u32 overflow issue in map batch operations
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Andrii Nakryiko <andrii@kernel.org>,
 Eduard <eddyz87@gmail.com>, Alexei Starovoitov <ast@kernel.org>,
 Daniel Borkmann <daniel@iogearbox.net>,
 Kumar Kartikeya Dwivedi <memxor@gmail.com>,
 Martin KaFai Lau <martin.lau@linux.dev>, Song Liu <song@kernel.org>,
 Yonghong Song <yonghong.song@linux.dev>, Jiri Olsa <jolsa@kernel.org>,
 Emil Tsalapatis <emil@etsalapatis.com>,
 Ihor Solodrai <ihor.solodrai@linux.dev>,
 John Fastabend <john.fastabend@gmail.com>, Brian Vazquez <brianvv@google.com>
References: <20260902204439.287888-1-maghasi@disroot.org>
 <20260903082734.623904-1-maghasi@disroot.org>
 <CAADnVQLX5bjLTPm8Ch0wNuojHrKw6R5iJDBRsMJwrWMSupVwew@mail.gmail.com>
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From: Masoud Aghasi <maghasi@disroot.org>
In-Reply-To: <CAADnVQLX5bjLTPm8Ch0wNuojHrKw6R5iJDBRsMJwrWMSupVwew@mail.gmail.com>
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On 04/09/2026 05:45, Alexei Starovoitov wrote:
> On Thu, Sep 3, 2026 at 1:28 AM Masoud Aghasi <maghasi@disroot.org> wrote:
>>
>> Several map batch operation implementations such as
>> generic_map_lookup_batch() use calculations in the form of
>> "values + cp * map->value_size" to compute the desired userspace memory
>> address for reading or writing. This can overflow the u32 type
>> (the result of "cp * map->value_size") when the map size exceeds 4GB.
>>
>> generic_map_lookup_batch() may corrupt values for some keys in
>> userspace memory, and in some cases it mismatches values for some keys
>> while still reporting success.
> 
> without selftest I have to assume that this is AI hallucination.
> 
> pw-bot: cr

And here is the output of the same test after patching the kernel:
$ sudo ./test_progs -t map_batch_overflow
#212/1   map_batch_overflow/array_lookup:OK
#212/2   map_batch_overflow/array_lookup_4gb_plus:OK
#212/3   map_batch_overflow/array_update:OK
#212/4   map_batch_overflow/array_update_4gb_plus:OK
#212     map_batch_overflow:OK
Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED

Sorry for replying in multiple emails.