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Fri, 10 Jan 2025 08:43:32 -0800 (PST) Date: Fri, 10 Jan 2025 08:43:28 -0800 From: Isaac Manjarres To: Lorenzo Stoakes Cc: Andrew Morton , kaleshsingh@google.com, jstultz@google.com, aliceryhl@google.com, surenb@google.com, kernel-team@android.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] mm/memfd: Use strncpy_from_user() to read memfd name Message-ID: References: <20250109185908.1006310-1-isaacmanjarres@google.com> <20250109185908.1006310-3-isaacmanjarres@google.com> <38fbe522-f757-4de9-acf3-1483b90898f6@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <38fbe522-f757-4de9-acf3-1483b90898f6@lucifer.local> X-Rspamd-Server: rspam05 X-Stat-Signature: 3pskbawoxq6pgmasn4rzotibipebi5ji X-Rspamd-Queue-Id: 6C7C214000B X-Rspam-User: X-HE-Tag: 1736527414-142670 X-HE-Meta: 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 5Op4jT1U OZLoipoPJrg5856mjBWx7+CaFmMpl7fT+Heky/PrpenXQqQBh4JBQe43VVlO9aRK6Pl5RuYzpYcMfVILnx9pfwbJ89UO8vzXglot2OGLLWYBQKKCEHR5N4UiE/TNfg7OyFFOocqdUlrTPz/dIlI+8uEGs9ZXnkC4HKC6Qg5kc0K+Kdyd9L/YjoILin766AbmDTrka2tEvtxV81pXUTug7N6ZA1GXo96o5SCvl0PqCN9cGCbak7JH6+OAX9fOjMUfKV3ydEiKEzOKjeqS3x+XUyi5gKfLuFKr65xJzBlZZzx9Rhx7HBBrF1Als55TqWwmkOMx/pMgbW/8bx+YywmLwvQUBC/HYppRWcGFWkkG3o//izozfGs9ZyFM1lb0eKWFNqcj/vQiqROy+P93XyMnu27LAghM5w1HqPvh8Ix8FYG2LIMc= X-Bogosity: Unsure, tests=bogofilter, spamicity=0.468252, 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 Fri, Jan 10, 2025 at 12:48:44PM +0000, Lorenzo Stoakes wrote: > On Thu, Jan 09, 2025 at 10:59:05AM -0800, Isaac J. Manjarres wrote: > > The existing logic uses strnlen_user() to calculate the length of the > > memfd name from userspace and then copies the string into a buffer using > > copy_from_user(). This is error-prone, as the string length > > could have changed between the time when it was calculated and when the > > string was copied. The existing logic handles this by ensuring that the > > last byte in the buffer is the terminating zero. > > > > This handling is contrived and can better be handled by using > > strncpy_from_user(), which gets the length of the string and copies > > it in one shot. Therefore, simplify the logic for copying the memfd > > name by using strncpy_from_user(). > > > > No functional change. > > > > Reviewed-by: Alice Ryhl > > Signed-off-by: Isaac J. Manjarres > > LGTM, > > Reviewed-by: Lorenzo Stoakes > Thank you! --Isaac