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b=T4A6vh6cbK6ZufKbZhNi3k1K95qYH460093V3SDwP3w3NF0b1mDzp9VAZ1trcsTaf HPYAU/BozaKvBziW+zGOBpW8jWVHUzaUILaPCAFaWiUwMlRnYSfMrYSBVopGX0WKka oDG2/p0IJAZuyOy1jiJWFNNy7f85NoRWCDus+XlOiqLkwpalyOsz6deVpSKVRDah39 SpekqTn+vU3RCz0IjjNRDzSNc7p3HrP+Z8dQK8h6ySFLB6yLW3t0BmGig7p54AqLLi fz5pGEMUZ0KCNRudvLF8WbmUscL/Ig2eHHhGDIvbLxNaIqQr80RuExsjsWDVcF4Wjc vNv9Cp51/3Dpw== Date: Wed, 11 Sep 2024 14:31:16 +0200 From: Danilo Krummrich To: Benno Lossin Cc: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, a.hindborg@samsung.com, aliceryhl@google.com, akpm@linux-foundation.org, daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v6 22/26] rust: alloc: implement `Cmalloc` in module allocator_test Message-ID: References: <20240816001216.26575-1-dakr@kernel.org> <20240816001216.26575-23-dakr@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 740822001C X-Stat-Signature: snwfgsod9zobd66q6j7ut1oqz5demazd X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1726057885-171261 X-HE-Meta: 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 OaQ76Nzw MfFsauTu8fVCc3tRkxpAexF9bQmpGUAb2yGFE9mOHwcYgLQ+jJHphTDsgIWDmKY4OiNyUPa4OFUZYWjun7luglYhEinODvcRAVuSCLEqA4023K7RPWOBbyvCpwbYKryXhn+NHvyyhVO+wkSPViTdbQOlFLNxhpa9lkJ6lKNvUSe59BEgUN/OOUF5IhAN+O25L14/XU7F7hpTQa4QSS3muMMI8Z926gIZLLADLVSDIOvgRzwiqysSG/ProX23dnYUQrJavNPn5/z5n+Q0aWWvid7/QOy10f1P3r0yh+SQLMKyuSdX1dlhQoMdetxCd/bnG3uFOlZSHP5OXy78n497sVefc7lC1X7DDgmi8 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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, Aug 30, 2024 at 12:25:27AM +0200, Danilo Krummrich wrote: > On Thu, Aug 29, 2024 at 07:14:18PM +0000, Benno Lossin wrote: > > On 16.08.24 02:11, Danilo Krummrich wrote: > > > > > + > > > + if layout.size() == 0 { > > > + // SAFETY: `src` has been created by `Self::alloc_store_data`. > > > > This is not true, consider: > > > > let ptr = alloc(size = 0); > > free(ptr) > > > > Alloc will return a dangling pointer due to the first if statement and > > then this function will pass it to `free_read_data`, even though it > > wasn't created by `alloc_store_data`. > > This isn't forbidden by the `Allocator` trait function's safety > > requirements. > > > > > + unsafe { Self::free_read_data(src) }; > > > + > > > + return Ok(NonNull::slice_from_raw_parts(NonNull::dangling(), 0)); > > > + } > > > + > > > + let dst = Self::alloc(layout, flags)?; > > > + > > > + // SAFETY: `src` has been created by `Self::alloc_store_data`. > > > + let data = unsafe { Self::data(src) }; > > > > Same issue here, if the allocation passed in is zero size. I think you > > have no other choice than to allocate even for zero size requests... > > Otherwise how would you know that they are zero-sized. > > Good catch - gonna fix it. Almost got me. :) I think the code is fine, callers are not allowed to pass pointers to `realloc` and `free`, which haven't been allocated with the same corresponding allocator or are dangling. > > > > > --- > > Cheers, > > Benno > > > > > + > > > + // SAFETY: `src` has previously been allocated with this `Allocator`; `dst` has just been > > > + // newly allocated. Copy up to the smaller of both sizes. > > > + unsafe { > > > + ptr::copy_nonoverlapping( > > > + src.as_ptr(), > > > + dst.as_ptr().cast(), > > > + cmp::min(layout.size(), data.size), > > > + ) > > > + }; > > > + > > > + // SAFETY: `src` has been created by `Self::alloc_store_data`. > > > + unsafe { Self::free_read_data(src) }; > > > + > > > + Ok(dst) > > > } > > > } > > > -- > > > 2.46.0 > > > > >