From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=213.167.242.64 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794444044; b=c9fGvT/ASGcW/VdLY5Lmr/eyYJbFD1zOiMWhmYGxRNxw/4+K2cPZCl7DfVSShTarWF6I xDHDMmd/EcGTRl8Ad4iQfggqN6KBWodYJCqh9Pg/Tz9F2u83R+WTrsL9dSowk+wIUoZRt JpLqQZjHHn++bU3/5rszyGoBrUvdytC+iA2/Ry+QDgUj5HskFEU1BYgYNE/sDyGfP0zPt SBEm+opk7kP7e5Ia8hSIvqK4rb/4vw7mGFtvH5n2sfr1+UcsUTrlO4N/KvgTf0GsEX0Iz K+Ph77eJf0bnzCsAl+SvJy3t4M72V8VH/yWYIhasYA+TlZR7vmXJ83eM/cvo/LB9jeQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794444044; h=DMARC-Filter:Received:DKIM-Signature:Date:From:To:Cc:Subject: Message-ID:References:MIME-Version:Content-Type:Content-Disposition: In-Reply-To; bh=6xpWvm8FwNjmg+fPN53wD4gkIM4E/p3REBlACqtLvXs=; b=BaIqGb1wKlt0IfSxIL8o0kH0AIcv+7Grj4AyN762Il4uaAP5Ia+2RFJdhIQOKESj93Uj 9goKnfOEmZZl60nlvJijbSjD6UL24ZDW1j+HN6pixupfOsvp6ZAemfMAPmY1HnvlyIm6Z VhTcVGSLNsKxxQ0X6fyqdDgWyM3CHU8QKh00xsYuMmlLCfbbXaiddWfLfVWhha2UqW9u4 Ag3QrkPDgXEDxGnoNwCL85RP+/aJcBBjl8+MnEanSNToBm4+KhNUjjfa6EtrjBOh11K4t XTg5YTbIaymaZmGnS1XVuaHUXfbeyRGqNTTZD/04j5gwCxIupKJBNGaIzuYiCD54C2w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass header.d=ideasonboard.com header.i=@ideasonboard.com header.a=rsa-sha256 header.s=mail header.b=OwAplIni; arc=none smtp.remote-ip=213.167.242.64 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 754A9606A32D for ; Thu, 12 Nov 2026 00:40:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 754A9606A32D Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.a=rsa-sha256 header.s=mail header.b=OwAplIni Received: from killaraus.ideasonboard.com (2001-14ba-7086-3000--a06.rev.dnainternet.fi [IPv6:2001:14ba:7086:3000::a06]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 5C75A1F8; Thu, 12 Nov 2026 01:38:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1794443897; bh=xqfnEjqyHMQl2qHFWowUXzE/Oqfvp6pljb9uxPDED6A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OwAplIniUURguBikb+R/YMs3Bk8BOTl5EYLwv+82bdKT0dPNZJZiMnz9j+W0pHvef FtqWTyR04z/5aW7g+jR/himpZlnP3HJ9YmG522bYVRRYPgmf8uA6/vCIJj0CspD307 tAoFk2kEEVq48RsFodiAydmT/svA8mDID9+hwG6E= Date: Thu, 12 Nov 2026 02:40:39 +0200 From: Laurent Pinchart To: Kees Cook Cc: Greg Kroah-Hartman , "Rafael J. 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-Mailing-List: driver-core@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260914223219.901347-2-kees@kernel.org> 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