linux-kernel - [PATCH 10/12] module: Factor out elf_validity_cache

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Message-ID: <20241015231651.3851138-11-mmaurer@google.com>
Date: Tue, 15 Oct 2024 23:16:44 +0000
From: Matthew Maurer <mmaurer@...gle.com>
To: mcgrof@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org, 
	samitolvanen@...gle.com, Matthew Maurer <mmaurer@...gle.com>, 
	Petr Pavlu <petr.pavlu@...e.com>, Daniel Gomez <da.gomez@...sung.com>
Subject: [PATCH 10/12] module: Factor out elf_validity_cache_strtab

This patch only moves the existing strtab population to a function.
Validation comes in a following patch, this is split out to make the new
validation checks more clearly separated.

Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
---
 kernel/module/main.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index f352c73b6f40..22aa5eb4e4f4 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2122,6 +2122,23 @@ static int elf_validity_cache_index(struct load_info *info, int flags)
 	return 0;
 }
 
+/**
+ * elf_validity_cache_strtab() - Cache symbol string table
+ * @info: Load info to read from and update.
+ *        Must have &load_info->sechdrs and &load_info->secstrings populated.
+ *        Must have &load_info->index populated.
+ *
+ * Return: 0 on success, negative error code if a check failed.
+ */
+static int elf_validity_cache_strtab(struct load_info *info)
+{
+	Elf_Shdr *str_shdr = &info->sechdrs[info->index.str];
+	char *strtab = (char *)info->hdr + str_shdr->sh_offset;
+
+	info->strtab = strtab;
+	return 0;
+}
+
 /*
  * Check userspace passed ELF module against our expectations, and cache
  * useful variables for further processing as we go.
@@ -2155,9 +2172,9 @@ static int elf_validity_cache_copy(struct load_info *info, int flags)
 	err = elf_validity_cache_index(info, flags);
 	if (err < 0)
 		return err;
-
-	/* Sets internal strings. */
-	info->strtab = (char *)info->hdr + info->sechdrs[info->index.str].sh_offset;
+	err = elf_validity_cache_strtab(info);
+	if (err < 0)
+		return err;
 
 	/* This is temporary: point mod into copy of data. */
 	info->mod = (void *)info->hdr + info->sechdrs[info->index.mod].sh_offset;
-- 
2.47.0.rc1.288.g06298d1525-goog