diff mbox series

[08/12] module: Factor out elf_validity_cache_index_str

Message ID 20241015231651.3851138-9-mmaurer@google.com (mailing list archive)
State Handled Elsewhere
Headers show
Series Module Validation Refactor | expand

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Commit Message

Matthew Maurer Oct. 15, 2024, 11:16 p.m. UTC 
Pull out index validation for the symbol string section.

Note that this does not validate the *contents* of the string table,
only shape and presence of the section.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
---
 kernel/module/main.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 955746649f37..a6bed293d97b 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2047,6 +2047,31 @@  static int elf_validity_cache_index_sym(struct load_info *info)
 	return 0;
 }
 
+/**
+ * elf_validity_cache_index_str() - Validate and cache strtab index
+ * @info: Load info to cache strtab index in.
+ *        Must have &load_info->sechdrs and &load_info->secstrings populated.
+ *        Must have &load_info->index.sym populated.
+ *
+ * Looks at the symbol table's associated string table, makes sure it is
+ * in-bounds, and caches it.
+ *
+ * Return: %0 if valid, %-ENOEXEC on failure.
+ */
+static int elf_validity_cache_index_str(struct load_info *info)
+{
+	unsigned int str_idx = info->sechdrs[info->index.sym].sh_link;
+
+	if (str_idx == SHN_UNDEF || str_idx >= info->hdr->e_shnum) {
+		pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
+		       str_idx, str_idx, info->hdr->e_shnum);
+		return -ENOEXEC;
+	}
+
+	info->index.str = str_idx;
+	return 0;
+}
+
 /*
  * Check userspace passed ELF module against our expectations, and cache
  * useful variables for further processing as we go.
@@ -2070,7 +2095,6 @@  static int elf_validity_cache_index_sym(struct load_info *info)
 static int elf_validity_cache_copy(struct load_info *info, int flags)
 {
 	int err;
-	int str_idx;
 
 	err = elf_validity_cache_sechdrs(info);
 	if (err < 0)
@@ -2087,16 +2111,11 @@  static int elf_validity_cache_copy(struct load_info *info, int flags)
 	err = elf_validity_cache_index_sym(info);
 	if (err < 0)
 		return err;
-
-	str_idx = info->sechdrs[info->index.sym].sh_link;
-	if (str_idx == SHN_UNDEF || str_idx >= info->hdr->e_shnum) {
-		pr_err("Invalid ELF sh_link!=SHN_UNDEF(%d) or (sh_link(%d) >= hdr->e_shnum(%d)\n",
-				str_idx, str_idx, info->hdr->e_shnum);
-		return -ENOEXEC;
-	}
+	err = elf_validity_cache_index_str(info);
+	if (err < 0)
+		return err;
 
 	/* Sets internal strings. */
-	info->index.str = str_idx;
 	info->strtab = (char *)info->hdr + info->sechdrs[info->index.str].sh_offset;
 
 	/* This is temporary: point mod into copy of data. */