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>
This commit is contained in:
Linus Torvalds 2010-10-05 11:29:27 -07:00
parent 2f6b3aa7a5
commit 5336377d62
11 changed files with 14 additions and 26 deletions

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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);
}

View File

@ -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 */

View File

@ -1537,6 +1537,7 @@ static int __unlink_module(void *_mod)
{
struct module *mod = _mod;
list_del(&mod->list);
module_bug_cleanup(mod);
return 0;
}
@ -2625,6 +2626,7 @@ static struct module *load_module(void __user *umod,
if (err < 0)
goto ddebug;
module_bug_finalize(info.hdr, info.sechdrs, mod);
list_add_rcu(&mod->list, &modules);
mutex_unlock(&module_mutex);
@ -2650,6 +2652,8 @@ static 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:
if (!mod->taints)
dynamic_debug_remove(info.debug);

View File

@ -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)