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Message-ID: <20240806212106.617164-9-mmaurer@google.com>
Date: Tue, 6 Aug 2024 21:20:34 +0000
From: Matthew Maurer <mmaurer@...gle.com>
To: masahiroy@...nel.org, ndesaulniers@...gle.com, ojeda@...nel.org,
gary@...yguo.net, mcgrof@...nel.org, Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>
Cc: Matthew Maurer <mmaurer@...gle.com>, rust-for-linux@...r.kernel.org,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, neal@...pa.dev,
marcan@...can.st, j@...nau.net, asahi@...ts.linux.dev,
Boqun Feng <boqun.feng@...il.com>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...sung.com>, Alice Ryhl <aliceryhl@...gle.com>,
linux-modules@...r.kernel.org
Subject: [PATCH v3 08/16] 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 53597b785e2a..dec733989ad6 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2014,6 +2014,31 @@ 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.
@@ -2037,7 +2062,6 @@ 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)
@@ -2054,16 +2078,11 @@ 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. */
--
2.46.0.rc2.264.g509ed76dc8-goog
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