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R. Silva" , linux-kernel@vger.kernel.org (open list), linux-hardening@vger.kernel.org (open list:KERNEL HARDENING (not covered by other areas):Keyword:\b__counted_by(_le|_be)?\b) Subject: [PATCH 1/2] mtd: virt_concat: use single allocation for node Date: Wed, 4 Mar 2026 14:15:29 -0800 Message-ID: <20260304221530.15018-2-rosenp@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260304221530.15018-1-rosenp@gmail.com> References: <20260304221530.15018-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Simpler to reason about and avoids having to free nodes separately. Also add __counted_by attribute for extra runtime analysis. Signed-off-by: Rosen Penev --- drivers/mtd/mtd_virt_concat.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/drivers/mtd/mtd_virt_concat.c b/drivers/mtd/mtd_virt_concat.c index aea88d1c9bc5..89e223edac6a 100644 --- a/drivers/mtd/mtd_virt_concat.c +++ b/drivers/mtd/mtd_virt_concat.c @@ -31,8 +31,8 @@ static LIST_HEAD(concat_node_list); struct mtd_virt_concat_node { struct list_head head; unsigned int count; - struct device_node **nodes; struct mtd_concat *concat; + struct device_node *nodes[] __counted_by(nodes); }; =20 /** @@ -133,7 +133,6 @@ int mtd_virt_concat_destroy(struct mtd_info *mtd) for (idx =3D 0; idx < item->count; idx++) of_node_put(item->nodes[idx]); =20 - kfree(item->nodes); kfree(item); } return 0; @@ -167,16 +166,11 @@ static int mtd_virt_concat_create_item(struct device_= node *parts, return 0; } =20 - item =3D kzalloc(sizeof(*item), GFP_KERNEL); + item =3D kzalloc_flex(*item, nodes, count, GFP_KERNEL); if (!item) return -ENOMEM; =20 item->count =3D count; 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Wed, 04 Mar 2026 14:15:51 -0800 (PST) Received: from ryzen ([2601:644:8000:56f5::8bd]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c70fa6203a6sm17637399a12.8.2026.03.04.14.15.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Mar 2026 14:15:50 -0800 (PST) From: Rosen Penev To: linux-mtd@lists.infradead.org Cc: Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Kees Cook , "Gustavo A. R. Silva" , linux-kernel@vger.kernel.org (open list), linux-hardening@vger.kernel.org (open list:KERNEL HARDENING (not covered by other areas):Keyword:\b__counted_by(_le|_be)?\b) Subject: [PATCH 2/2] mtd: concat: replace alloc + calloc with 1 alloc Date: Wed, 4 Mar 2026 14:15:30 -0800 Message-ID: <20260304221530.15018-3-rosenp@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260304221530.15018-1-rosenp@gmail.com> References: <20260304221530.15018-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A flex array can be used to reduce the allocation to 1. And actually mtdconcat was using the pointer + 1 trick to point to the overallocated area. Better alternatives exist. Signed-off-by: Rosen Penev --- drivers/mtd/mtd_virt_concat.c | 10 ++-------- drivers/mtd/mtdconcat.c | 5 +---- include/linux/mtd/concat.h | 2 +- 3 files changed, 4 insertions(+), 13 deletions(-) diff --git a/drivers/mtd/mtd_virt_concat.c b/drivers/mtd/mtd_virt_concat.c index 89e223edac6a..b56f2431974b 100644 --- a/drivers/mtd/mtd_virt_concat.c +++ b/drivers/mtd/mtd_virt_concat.c @@ -32,7 +32,7 @@ struct mtd_virt_concat_node { struct list_head head; unsigned int count; struct mtd_concat *concat; - struct device_node *nodes[] __counted_by(nodes); + struct device_node *nodes[] __counted_by(count); }; =20 /** @@ -182,18 +182,12 @@ static int mtd_virt_concat_create_item(struct device_= node *parts, for (i =3D 1; i < count; i++) item->nodes[i] =3D of_parse_phandle(parts, CONCAT_PROP, (i - 1)); =20 - concat =3D kzalloc(sizeof(*concat), GFP_KERNEL); + concat =3D kzalloc_flex(*concat, subdev, count, GFP_KERNEL); if (!concat) { kfree(item); return -ENOMEM; } =20 - concat->subdev =3D kcalloc(count, sizeof(*concat->subdev), GFP_KERNEL); - if (!concat->subdev) { - kfree(item); - kfree(concat); - return -ENOMEM; - } item->concat =3D concat; =20 list_add_tail(&item->head, &concat_node_list); diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c index 241d15235d01..c97167d51fe2 100644 --- a/drivers/mtd/mtdconcat.c +++ b/drivers/mtd/mtdconcat.c @@ -627,7 +627,6 @@ struct mtd_info *mtd_concat_create(struct mtd_info *sub= dev[], /* subdevices to c const char *name) { /* name for the new device */ int i; - size_t size; struct mtd_concat *concat; struct mtd_info *subdev_master =3D NULL; uint32_t max_erasesize, curr_erasesize; @@ -640,15 +639,13 @@ struct mtd_info *mtd_concat_create(struct mtd_info *s= ubdev[], /* subdevices to c printk(KERN_NOTICE "into device \"%s\"\n", name); =20 /* allocate the device structure */ - size =3D SIZEOF_STRUCT_MTD_CONCAT(num_devs); - concat =3D kzalloc(size, GFP_KERNEL); + concat =3D kzalloc_flex(*concat, subdev, num_devs, GFP_KERNEL); if (!concat) { printk ("memory allocation error while creating concatenated device \"%s\"\= n", name); return NULL; } - concat->subdev =3D (struct mtd_info **) (concat + 1); =20 /* * Set up the new "super" device's MTD object structure, check for diff --git a/include/linux/mtd/concat.h b/include/linux/mtd/concat.h index 2cd9d48958a8..f8d4d6ac1fc1 100644 --- a/include/linux/mtd/concat.h +++ b/include/linux/mtd/concat.h @@ -18,7 +18,7 @@ struct mtd_concat { struct mtd_info mtd; int num_subdev; - struct mtd_info **subdev; + struct mtd_info *subdev[]; }; =20 struct mtd_info *mtd_concat_create( --=20 2.53.0