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Wysocki" , Danilo Krummrich , "Gustavo A. R. Silva" , driver-core@lists.linux.dev, linux-hardening@vger.kernel.org, Lorenzo Stoakes , Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , David Hildenbrand , "Liam R. Howlett" , Mike Rapoport , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Geert Uytterhoeven Subject: Re: [PATCH 2/2] devres: Provide kmalloc_obj*-style API for devm_kmalloc Message-ID: <20261112004039.GA523044@killaraus.ideasonboard.com> References: <20260914223212.i.829-kees@kernel.org> <20260914223219.901347-2-kees@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260914223219.901347-2-kees@kernel.org> X-Stat-Signature: s4w1afrzaau4anqomc4ksnige4jq4hg5 X-Rspamd-Queue-Id: 8C5EF2000A X-Rspam-User: X-Rspamd-Server: rspam08 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1794444044-216299 X-HE-Meta: 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 iSWnymmG mB0ghi7tON9RcXd2+NzWG3cuiq7uJl1dhUVR1hpSQymLHksf7W93EYcpHlNjRqSji768esRagBAJeswAJV5XyJ2hxiW8iJOI+jIYSGKm/xEhuQ9H0z9gWlBCWeZCxTAcggvMR9dCY42VTIIU9MgVxY4PQYMIHthBVURCUoiOE7OvtlSAwiRVgQNIbxFjelgdDY7X2IceL5eaf9r3cQ1FP6DSwTtSDVI1wXOASVbBS4B39Ue0Yw98KmsJa9sWGH7ECSkUedMG5xz8DEhpig1LGp3sY59XcIuCRFlWM3om+BBY7FrA7EJ37JJ1xrCOk3D+AWBVtwj53tNyJoHjxkZdCYxBHtpBE28oJcSULkMfyejtsJx90WEcPGLjc52CI20oyHt+i/cr6mJiOeoXXNoc+4boZ24/B+lcL5agEAP0lElMeLsGIn35E7qGYlQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi Kees, On Mon, Sep 14, 2026 at 03:32:17PM -0700, Kees Cook wrote: > Mirroring the type-based allocation now in use for the kmalloc family of > APIs, provide the same for the devm_kmalloc family of APIs. This will > allow for future plumbing of type information (e.g. alignment) into the > underlying allocations. This immediately gains type check on return > values (instead of the prior "void *" return type). > > Signed-off-by: Kees Cook > --- > Cc: Greg Kroah-Hartman > Cc: "Rafael J. Wysocki" > Cc: Danilo Krummrich > Cc: "Gustavo A. R. Silva" > Cc: > Cc: > --- > include/linux/device/devres.h | 102 ++++++++++++++++++++++++++++++++++ > 1 file changed, 102 insertions(+) > > diff --git a/include/linux/device/devres.h b/include/linux/device/devres.h > index 14ab9159bdda..7656c9ecd4da 100644 > --- a/include/linux/device/devres.h > +++ b/include/linux/device/devres.h > @@ -62,6 +62,108 @@ static inline void *devm_kcalloc(struct device *dev, size_t n, size_t size, gfp_ > { > return devm_kmalloc_array(dev, n, size, flags | __GFP_ZERO); > } > + > +/** > + * __devm_alloc_objs - Device-managed allocation of objects of a given type > + * @DEVM_ALLOC: which device-managed size-based allocator to use. > + * @DEV: device to scope the allocation lifetime to. > + * @GFP: GFP flags for the allocation. > + * @TYPE: type to allocate space for. > + * @COUNT: how many @TYPE objects to allocate. > + * > + * Device-managed counterpart of __alloc_objs(). > + * @DEVM_ALLOC takes (@DEV, size, gfp). > + * > + * Returns: Newly allocated pointer to (first) @TYPE of @COUNT-many allocated > + * @TYPE objects, or NULL on failure. > + */ > +#define __devm_alloc_objs(DEVM_ALLOC, DEV, GFP, TYPE, COUNT) \ > +({ \ > + const size_t __obj_size = size_mul(sizeof(TYPE), COUNT); \ > + (TYPE *)DEVM_ALLOC(DEV, __obj_size, GFP); \ > +}) > + > +/** > + * devm_kmalloc_obj - Device-managed allocation of a single typed object > + * @DEV: Device to scope the allocation lifetime to. > + * @VAR_OR_TYPE: Variable or type to allocate. > + * @GFP: Optional GFP flags (defaults to %GFP_KERNEL). > + * > + * Device-managed counterpart of kmalloc_obj(): the allocation is sized from > + * @VAR_OR_TYPE and returned as a pointer to that type, not void *. > + * > + * Returns: newly allocated pointer to a @VAR_OR_TYPE on success, or NULL on > + * failure. > + */ > +#define devm_kmalloc_obj(DEV, VAR_OR_TYPE, ...) \ > + __devm_alloc_objs(devm_kmalloc, DEV, default_gfp(__VA_ARGS__), \ > + typeof(VAR_OR_TYPE), 1) > + > +/** > + * devm_kmalloc_objs - Device-managed allocation of an array of a typed object > + * @DEV: Device to scope the allocation lifetime to. > + * @VAR_OR_TYPE: Variable or type to allocate an array of. > + * @COUNT: How many elements in the array. > + * @GFP: Optional GFP flags (defaults to %GFP_KERNEL). > + * > + * Returns: newly allocated pointer to an array of @VAR_OR_TYPE on success, or > + * NULL on failure (including when the total size overflows). > + */ > +#define devm_kmalloc_objs(DEV, VAR_OR_TYPE, COUNT, ...) \ > + __devm_alloc_objs(devm_kmalloc, DEV, default_gfp(__VA_ARGS__), \ > + typeof(VAR_OR_TYPE), COUNT) > + > +/** > + * __devm_alloc_flex - Device-managed allocation of a trailing-flex-array object > + * @DEVM_ALLOC: which device-managed allocator to use. > + * @DEV: device to scope the allocation lifetime to. > + * @GFP: GFP flags for the allocation. > + * @TYPE: type of structure to allocate space for. > + * @FAM: name of the flexible array member of @TYPE. > + * @COUNT: how many @FAM elements to allocate space for. > + * > + * Device-managed counterpart of __alloc_flex(). > + * @DEVM_ALLOC takes (@DEV, size, gfp). > + * > + * Returns: Newly allocated pointer to @TYPE with @COUNT-many trailing @FAM > + * elements, or NULL on failure. > + */ > +#define __devm_alloc_flex(DEVM_ALLOC, DEV, GFP, TYPE, FAM, COUNT) \ > +({ \ > + const size_t __count = (COUNT); \ > + const size_t __obj_size = struct_size_t(TYPE, FAM, __count); \ > + TYPE *__obj_ptr = DEVM_ALLOC(DEV, __obj_size, GFP); \ > + if (__obj_ptr) \ > + __set_flex_counter(__obj_ptr->FAM, __count); \ > + __obj_ptr; \ > +}) > + > +/** > + * devm_kmalloc_flex - Device-managed allocation of a flexible-array structure > + * @DEV: Device to scope the allocation lifetime to. > + * @VAR_OR_TYPE: Variable or type to allocate (with its flexible array). > + * @FAM: The name of the flexible array member of the structure. > + * @COUNT: How many flexible array member elements to allocate. > + * @GFP: Optional GFP flags (defaults to %GFP_KERNEL). > + * > + * Returns: newly allocated pointer to @VAR_OR_TYPE on success, or NULL on > + * failure. If @FAM has been annotated with __counted_by(), its counter is set > + * to @COUNT. > + */ > +#define devm_kmalloc_flex(DEV, VAR_OR_TYPE, FAM, COUNT, ...) \ > + __devm_alloc_flex(devm_kmalloc, DEV, default_gfp(__VA_ARGS__), \ > + typeof(VAR_OR_TYPE), FAM, COUNT) > + > +/* All devm_kzalloc aliases for devm_kmalloc_(obj|objs|flex). */ > +#define devm_kzalloc_obj(DEV, P, ...) \ > + __devm_alloc_objs(devm_kzalloc, DEV, default_gfp(__VA_ARGS__), typeof(P), 1) > +#define devm_kzalloc_objs(DEV, P, COUNT, ...) \ > + __devm_alloc_objs(devm_kzalloc, DEV, default_gfp(__VA_ARGS__), \ > + typeof(P), COUNT) I was recently made aware by Geert of an unfortunate side effect of the default GPF_KERNEL argument. I've fixed a memory leak in the imx8-isi driver by using devm_kzalloc_objs() as follows: diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c index 0ae5f35e017c..9373a5256224 100644 --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c @@ -488,7 +488,8 @@ static int mxc_isi_probe(struct platform_device *pdev) isi->pdata = of_device_get_match_data(dev); - isi->pipes = kzalloc_objs(isi->pipes[0], isi->pdata->num_channels); + isi->pipes = devm_kzalloc_objs(dev, isi->pipes[0], + isi->pdata->num_channels); if (!isi->pipes) return -ENOMEM; So far, so good. However, the following code also compiles: isi->pipes = devm_kzalloc_obj(dev, isi->pipes[0], isi->pdata->num_channels); (note the *obj* instead of *objs*) because the third argument is interpreted as gfp flags. It's clearly a bug, but one that the compiler doesn't catch. The typo is easy to make. Sparse catches the issue: drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c:491:22: warning: incorrect type in argument 3 (different base types) drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c:491:22: expected restricted gfp_t [usertype] gfp drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c:491:22: got unsigned int const num_channels I'm however not sure if build bots report sparse warnings or only errors. Is this an issue you're aware of, and do you think it should be addressed ? > +#define devm_kzalloc_flex(DEV, P, FAM, COUNT, ...) \ > + __devm_alloc_flex(devm_kzalloc, DEV, default_gfp(__VA_ARGS__), \ > + typeof(P), FAM, COUNT) > + > static inline __realloc_size(3, 4) void * __must_check > devm_krealloc_array(struct device *dev, void *p, size_t new_n, size_t new_size, gfp_t flags) > { -- Regards, Laurent Pinchart