linux-kernel - [PATCH 2/4] module: sysfs: Simplify section attribute allocation

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Message-Id: <20241216-sysfs-const-bin_attr-module-v1-2-f81e49e54ce4@weissschuh.net>
Date: Mon, 16 Dec 2024 20:16:42 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>, 
 Sami Tolvanen <samitolvanen@...gle.com>, 
 Daniel Gomez <da.gomez@...sung.com>, Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-hardening@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 2/4] module: sysfs: Simplify section attribute allocation

The existing allocation logic manually stuffs two allocations into one.
This is hard to understand and of limited value, given that all the
section names are allocated on their own anyways.
Une one allocation per datastructure.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 kernel/module/sysfs.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
index b7841f76a933114e6dbd0fc2d32a60b66b7966b6..935629ac21fa16504ddb5f3762af5539572c3bf1 100644
--- a/kernel/module/sysfs.c
+++ b/kernel/module/sysfs.c
@@ -65,34 +65,37 @@ static void free_sect_attrs(struct module_sect_attrs *sect_attrs)
 
 	for (bin_attr = sect_attrs->grp.bin_attrs; *bin_attr; bin_attr++)
 		kfree((*bin_attr)->attr.name);
+	kfree(sect_attrs->grp.bin_attrs);
 	kfree(sect_attrs);
 }
 
 static int add_sect_attrs(struct module *mod, const struct load_info *info)
 {
-	unsigned int nloaded = 0, i, size[2];
 	struct module_sect_attrs *sect_attrs;
 	struct module_sect_attr *sattr;
 	struct bin_attribute **gattr;
+	unsigned int nloaded = 0, i;
 	int ret;
 
 	/* Count loaded sections and allocate structures */
 	for (i = 0; i < info->hdr->e_shnum; i++)
 		if (!sect_empty(&info->sechdrs[i]))
 			nloaded++;
-	size[0] = ALIGN(struct_size(sect_attrs, attrs, nloaded),
-			sizeof(sect_attrs->grp.bin_attrs[0]));
-	size[1] = (nloaded + 1) * sizeof(sect_attrs->grp.bin_attrs[0]);
-	sect_attrs = kzalloc(size[0] + size[1], GFP_KERNEL);
+	sect_attrs = kzalloc(struct_size(sect_attrs, attrs, nloaded), GFP_KERNEL);
 	if (!sect_attrs)
 		return -ENOMEM;
 
+	gattr = kcalloc(nloaded + 1, sizeof(*gattr), GFP_KERNEL);
+	if (!gattr) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
 	/* Setup section attributes. */
 	sect_attrs->grp.name = "sections";
-	sect_attrs->grp.bin_attrs = (void *)sect_attrs + size[0];
+	sect_attrs->grp.bin_attrs = gattr;
 
 	sattr = &sect_attrs->attrs[0];
-	gattr = &sect_attrs->grp.bin_attrs[0];
 	for (i = 0; i < info->hdr->e_shnum; i++) {
 		Elf_Shdr *sec = &info->sechdrs[i];
 
@@ -111,7 +114,6 @@ static int add_sect_attrs(struct module *mod, const struct load_info *info)
 		sattr->battr.attr.mode = 0400;
 		*(gattr++) = &(sattr++)->battr;
 	}
-	*gattr = NULL;
 
 	ret = sysfs_create_group(&mod->mkobj.kobj, &sect_attrs->grp);
 	if (ret)

-- 
2.47.1