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From: Kees Cook <keescook@chromium.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Jessica Yu <jeyu@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-arch@vger.kernel.org, Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Alexander Egorenkov <egorenar@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Ilya Leoshkevich <iii@linux.ibm.com>,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
	Ingo Molnar <mingo@kernel.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH 3/4] module: Use a list of strings for ro_after_init sections
Date: Wed,  1 Sep 2021 16:37:56 -0700	[thread overview]
Message-ID: <20210901233757.2571878-4-keescook@chromium.org> (raw)
In-Reply-To: <20210901233757.2571878-1-keescook@chromium.org>

Instead of open-coding the section names, use a list for the sections that
need to be marked read-only after init. Unfortunately, it seems we can't
do normal section merging with scripts/module.lds.S as ld.bfd doesn't
correctly update symbol tables. For more details, see commit 6a3193cdd5e5
("kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG
is enabled").

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-arch@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/asm-generic/vmlinux.lds.h |  4 +++-
 kernel/module.c                   | 28 ++++++++++++++++------------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 4781a8154254..d532baadaeae 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -418,7 +418,9 @@
 
 /*
  * Allow architectures to handle ro_after_init data on their
- * own by defining an empty RO_AFTER_INIT_DATA.
+ * own by defining an empty RO_AFTER_INIT_DATA. Any sections
+ * added here must be explicitly marked SHF_RO_AFTER_INIT
+ * via module_sections_ro_after_init[] in kernel/module.c.
  */
 #ifndef RO_AFTER_INIT_DATA
 #define RO_AFTER_INIT_DATA						\
diff --git a/kernel/module.c b/kernel/module.c
index ed13917ea5f3..b0ff82cc48fe 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3514,10 +3514,21 @@ static bool blacklisted(const char *module_name)
 }
 core_param(module_blacklist, module_blacklist, charp, 0400);
 
+/*
+ * List of sections to be marked read-only after init. This should match
+ * the RO_AFTER_INIT_DATA macro in include/asm-generic/vmlinux.lds.h.
+ */
+static const char * const module_sections_ro_after_init[] = {
+	".data..ro_after_init",
+	"__jump_table",
+	NULL
+};
+
 static struct module *layout_and_allocate(struct load_info *info, int flags)
 {
 	struct module *mod;
 	unsigned int ndx;
+	const char * const *section;
 	int err;
 
 	err = check_modinfo(info->mod, info, flags);
@@ -3543,18 +3554,11 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
 	 * layout_sections() can put it in the right place.
 	 * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set.
 	 */
-	ndx = find_sec(info, ".data..ro_after_init");
-	if (ndx)
-		info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
-	/*
-	 * Mark the __jump_table section as ro_after_init as well: these data
-	 * structures are never modified, with the exception of entries that
-	 * refer to code in the __init section, which are annotated as such
-	 * at module load time.
-	 */
-	ndx = find_sec(info, "__jump_table");
-	if (ndx)
-		info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
+	for (section = module_sections_ro_after_init; *section; section++) {
+		ndx = find_sec(info, *section);
+		if (ndx)
+			info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT;
+	}
 
 	/*
 	 * Determine total sizes, and put offsets in sh_entsize.  For now
-- 
2.30.2


  parent reply	other threads:[~2021-09-01 23:38 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-01 23:37 [PATCH 0/4] Fix ro_after_init vs static_call Kees Cook
2021-09-01 23:37 ` [PATCH 1/4] vmlinux.lds.h: Use regular *RODATA and *RO_AFTER_INIT_DATA suffixes Kees Cook
2021-09-03  5:55   ` Josh Poimboeuf
2021-09-03  8:17   ` Heiko Carstens
2021-09-01 23:37 ` [PATCH 2/4] vmlinux.lds.h: Split .static_call_sites from .static_call_tramp_key Kees Cook
2021-09-03  5:55   ` Josh Poimboeuf
2021-09-01 23:37 ` Kees Cook [this message]
2021-09-03  6:49   ` [PATCH 3/4] module: Use a list of strings for ro_after_init sections Josh Poimboeuf
2021-09-03 16:38     ` Kees Cook
2021-09-04  4:09       ` Josh Poimboeuf
2021-09-04 14:40         ` Kees Cook
2021-09-01 23:37 ` [PATCH 4/4] module: Include .static_call_sites in module ro_after_init Kees Cook

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