From 9aad2d11106f9a42593ee8eb3f10bc469873a18e Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 5 Oct 2010 11:29:27 -0700
Subject: [PATCH] modules: Fix module_bug_list list corruption race

With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.

Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 arch/avr32/kernel/module.c   |    3 +--
 arch/h8300/kernel/module.c   |    3 +--
 arch/mn10300/kernel/module.c |    3 +--
 arch/parisc/kernel/module.c  |    3 +--
 arch/powerpc/kernel/module.c |    5 -----
 arch/s390/kernel/module.c    |    3 +--
 arch/sh/kernel/module.c      |    2 --
 arch/x86/kernel/module.c     |    3 +--
 include/linux/module.h       |    5 ++---
 kernel/module.c              |    4 ++++
 lib/bug.c                    |    6 ++----
 11 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/arch/avr32/kernel/module.c b/arch/avr32/kernel/module.c
index 98f94d0..a727f54 100644
--- a/arch/avr32/kernel/module.c
+++ b/arch/avr32/kernel/module.c
@@ -314,10 +314,9 @@ int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 	vfree(module->arch.syminfo);
 	module->arch.syminfo = NULL;
 
-	return module_bug_finalize(hdr, sechdrs, module);
+	return 0;
 }
 
 void module_arch_cleanup(struct module *module)
 {
-	module_bug_cleanup(module);
 }
diff --git a/arch/h8300/kernel/module.c b/arch/h8300/kernel/module.c
index 0865e29..db4953d 100644
--- a/arch/h8300/kernel/module.c
+++ b/arch/h8300/kernel/module.c
@@ -112,10 +112,9 @@ int module_finalize(const Elf_Ehdr *hdr,
 		    const Elf_Shdr *sechdrs,
 		    struct module *me)
 {
-	return module_bug_finalize(hdr, sechdrs, me);
+	return 0;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
-	module_bug_cleanup(mod);
 }
diff --git a/arch/mn10300/kernel/module.c b/arch/mn10300/kernel/module.c
index 6aea7fd..196a111 100644
--- a/arch/mn10300/kernel/module.c
+++ b/arch/mn10300/kernel/module.c
@@ -206,7 +206,7 @@ int module_finalize(const Elf_Ehdr *hdr,
 		    const Elf_Shdr *sechdrs,
 		    struct module *me)
 {
-	return module_bug_finalize(hdr, sechdrs, me);
+	return 0;
 }
 
 /*
@@ -214,5 +214,4 @@ int module_finalize(const Elf_Ehdr *hdr,
  */
 void module_arch_cleanup(struct module *mod)
 {
-	module_bug_cleanup(mod);
 }
diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index 159a2b8..6e81bb5 100644
--- a/arch/parisc/kernel/module.c
+++ b/arch/parisc/kernel/module.c
@@ -941,11 +941,10 @@ int module_finalize(const Elf_Ehdr *hdr,
 	nsyms = newptr - (Elf_Sym *)symhdr->sh_addr;
 	DEBUGP("NEW num_symtab %lu\n", nsyms);
 	symhdr->sh_size = nsyms * sizeof(Elf_Sym);
-	return module_bug_finalize(hdr, sechdrs, me);
+	return 0;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
 	deregister_unwind_table(mod);
-	module_bug_cleanup(mod);
 }
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index 477c663..4ef93ae 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -65,10 +65,6 @@ int module_finalize(const Elf_Ehdr *hdr,
 	const Elf_Shdr *sect;
 	int err;
 
-	err = module_bug_finalize(hdr, sechdrs, me);
-	if (err)
-		return err;
-
 	/* Apply feature fixups */
 	sect = find_section(hdr, sechdrs, "__ftr_fixup");
 	if (sect != NULL)
@@ -101,5 +97,4 @@ int module_finalize(const Elf_Ehdr *hdr,
 
 void module_arch_cleanup(struct module *mod)
 {
-	module_bug_cleanup(mod);
 }
diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 22cfd63..f7167ee 100644
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -407,10 +407,9 @@ int module_finalize(const Elf_Ehdr *hdr,
 {
 	vfree(me->arch.syminfo);
 	me->arch.syminfo = NULL;
-	return module_bug_finalize(hdr, sechdrs, me);
+	return 0;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
-	module_bug_cleanup(mod);
 }
diff --git a/arch/sh/kernel/module.c b/arch/sh/kernel/module.c
index 43adddf..ae0be69 100644
--- a/arch/sh/kernel/module.c
+++ b/arch/sh/kernel/module.c
@@ -149,13 +149,11 @@ int module_finalize(const Elf_Ehdr *hdr,
 	int ret = 0;
 
 	ret |= module_dwarf_finalize(hdr, sechdrs, me);
-	ret |= module_bug_finalize(hdr, sechdrs, me);
 
 	return ret;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
-	module_bug_cleanup(mod);
 	module_dwarf_cleanup(mod);
 }
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index e0bc186..1c355c5 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -239,11 +239,10 @@ int module_finalize(const Elf_Ehdr *hdr,
 		apply_paravirt(pseg, pseg + para->sh_size);
 	}
 
-	return module_bug_finalize(hdr, sechdrs, me);
+	return 0;
 }
 
 void module_arch_cleanup(struct module *mod)
 {
 	alternatives_smp_module_del(mod);
-	module_bug_cleanup(mod);
 }
diff --git a/include/linux/module.h b/include/linux/module.h
index 8a6b9fd..aace066 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -686,17 +686,16 @@ extern int module_sysfs_initialized;
 
 
 #ifdef CONFIG_GENERIC_BUG
-int  module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
+void module_bug_finalize(const Elf_Ehdr *, const Elf_Shdr *,
 			 struct module *);
 void module_bug_cleanup(struct module *);
 
 #else	/* !CONFIG_GENERIC_BUG */
 
-static inline int  module_bug_finalize(const Elf_Ehdr *hdr,
+static inline void module_bug_finalize(const Elf_Ehdr *hdr,
 					const Elf_Shdr *sechdrs,
 					struct module *mod)
 {
-	return 0;
 }
 static inline void module_bug_cleanup(struct module *mod) {}
 #endif	/* CONFIG_GENERIC_BUG */
diff --git a/kernel/module.c b/kernel/module.c
index 6c56282..eca6e02 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1533,6 +1533,7 @@ static int __unlink_module(void *_mod)
 {
 	struct module *mod = _mod;
 	list_del(&mod->list);
+	module_bug_cleanup(mod);
 	return 0;
 }
 
@@ -2538,6 +2539,7 @@ static noinline struct module *load_module(void __user *umod,
 	if (err < 0)
 		goto ddebug;
 
+	module_bug_finalize(hdr, sechdrs, mod);
 	list_add_rcu(&mod->list, &modules);
 	mutex_unlock(&module_mutex);
 
@@ -2564,6 +2566,8 @@ static noinline struct module *load_module(void __user *umod,
 	mutex_lock(&module_mutex);
 	/* Unlink carefully: kallsyms could be walking list. */
 	list_del_rcu(&mod->list);
+	module_bug_cleanup(mod);
+
  ddebug:
 	dynamic_debug_remove(debug);
  unlock:
diff --git a/lib/bug.c b/lib/bug.c
index f13daf4..c005615 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -72,8 +72,8 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr)
 	return NULL;
 }
 
-int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
-			struct module *mod)
+void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
+			 struct module *mod)
 {
 	char *secstrings;
 	unsigned int i;
@@ -97,8 +97,6 @@ int module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
 	 * could potentially lead to deadlock and thus be counter-productive.
 	 */
 	list_add(&mod->bug_list, &module_bug_list);
-
-	return 0;
 }
 
 void module_bug_cleanup(struct module *mod)
-- 
1.7.6