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[2603:9001:3d00:5353::14c1]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d1798b75f0sm46001146d6.35.2024.10.29.14.31.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Oct 2024 14:31:09 -0700 (PDT) Message-ID: Date: Tue, 29 Oct 2024 17:31:08 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/3] nvmem: core: improve range check for nvmem_cell_write() To: Srinivas Kandagatla , Sebastian Reichel , Greg Kroah-Hartman , Maxime Ripard Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20241024154050.3245228-1-jberring@redhat.com> <20241024154050.3245228-2-jberring@redhat.com> <5b6901d9-f404-43b9-87eb-577124efa3f3@linaro.org> Content-Language: en-US From: Jennifer Berringer In-Reply-To: <5b6901d9-f404-43b9-87eb-577124efa3f3@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/29/24 13:55, Srinivas Kandagatla wrote: > if (!nvmem || nvmem->read_only || len != cell->bytes) >     return -EINVAL; > > Does this work? > > --srini I decided against this because it seems potentially useful to allow len to be less than cell->bytes when bit_offset is nonzero. I assumed that was the purpose of the original "cell->bit_offset == 0". For example, if a cell entry has the following field values { .bit_offset = 4, .nbits = 8, .bytes = 2, ...} then it would make sense to call nvmem_cell_write() with len=1 in order to write 8 bits. To allow that, I used "len > cell->bytes" instead of "!=" later in this function: >> @@ -1780,9 +1779,13 @@ static int __nvmem_cell_entry_write(struct nvmem_cell_entry *cell, void *buf, si >> return -EINVAL; >> if (cell->bit_offset || cell->nbits) { >> + if (len > cell->bytes) >> + return -EINVAL; >> buf = nvmem_cell_prepare_write_buffer(cell, buf, len); >> if (IS_ERR(buf)) >> return PTR_ERR(buf); >> + } else if (len != cell->bytes) { >> + return -EINVAL; >> } If you disagree with my reasoning then yes, your suggestion works and I can use that instead of what I wrote. None of the current in-tree callers of this function rely on that possibility I described. Thank you for the feedback. -Jennifer