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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4aa80f04723sm10842695e9.5.2026.10.28.11.38.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 11:38:32 -0700 (PDT) Date: Wed, 28 Oct 2026 18:38:30 +0000 From: David Laight To: Christoph Hellwig Cc: Reid Downing , Carlos Maiolino , linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, "Darrick J . Wong" , Eric Sandeen , Christoph Hellwig , stable@vger.kernel.org Subject: Re: [PATCH v2] xfs: fix wrong compat fields in xfs_ioctl32_bstat_copyin() Message-ID: <20261028183831.055627aa@pumpkin> In-Reply-To: References: <20261027161748.2760321-1-skibletz@gmail.com> <20261027164911.578ef6e7@pumpkin> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 28 Oct 2026 08:18:40 -0700 Christoph Hellwig wrote: > On Tue, Oct 27, 2026 at 04:49:11PM +0000, David Laight wrote: > > On Tue, 27 Oct 2026 12:17:48 -0400 > > Reid Downing wrote: > > > > > bs_blocks and bs_xflags were both read from bstat32->bs_size. > > > Read each one from its own field instead. > > > > It would be much better to do a single copy_from_user() of the entire > > compat structure and copy the fields to the standard one. > > Care to explain why it would be "much better" to do two copies instead of > one? The only benefits from copy_from/to_user over the current > get_put/user is avoidind the conctant user access disabling/enabling, That is a massive hit. The current code also has all the conditionals from access_ok(). > but the scoped uaccess thing would do the same. True, but unnecessarily 'technical' for this bit of code. You also save all the exception table entries - so the code size would be rather smaller. David