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Message-ID: <20241015231651.3851138-9-mmaurer@google.com>
Date: Tue, 15 Oct 2024 23:16:42 +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 08/12] module: Factor out elf_validity_cache_index_str
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@...gle.com>
---
kernel/module/main.c | 37 ++++++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)
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. */
--
2.47.0.rc1.288.g06298d1525-goog
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