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Message-Id: <200903171250.16585.rusty@rustcorp.com.au>
Date: Tue, 17 Mar 2009 12:50:15 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
"systemtap-ml" <systemtap@...rces.redhat.com>,
Eric Dumazet <dada1@...mosbay.com>
Subject: [PATCH] module: fix refptr allocation and release order
From: Masami Hiramatsu <mhiramat@...hat.com>
Impact: fix ref-after-free crash on failed module load
Fix refptr bug: Change refptr allocation and release order not to access a module
data structure pointed by 'mod' after freeing mod->module_core.
This bug will cause kernel panic(e.g. failed to find undefined symbols).
This bug was reported on systemtap bugzilla.
http://sources.redhat.com/bugzilla/show_bug.cgi?id=9927
Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Eric Dumazet <dada1@...mosbay.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index ba22484..1196f5d 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2015,14 +2015,6 @@ static noinline struct module *load_module(void __user *umod,
if (err < 0)
goto free_mod;
-#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)
- mod->refptr = percpu_modalloc(sizeof(local_t), __alignof__(local_t),
- mod->name);
- if (!mod->refptr) {
- err = -ENOMEM;
- goto free_mod;
- }
-#endif
if (pcpuindex) {
/* We have a special allocation for this section. */
percpu = percpu_modalloc(sechdrs[pcpuindex].sh_size,
@@ -2030,7 +2022,7 @@ static noinline struct module *load_module(void __user *umod,
mod->name);
if (!percpu) {
err = -ENOMEM;
- goto free_percpu;
+ goto free_mod;
}
sechdrs[pcpuindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
mod->percpu = percpu;
@@ -2082,6 +2074,14 @@ static noinline struct module *load_module(void __user *umod,
/* Module has been moved. */
mod = (void *)sechdrs[modindex].sh_addr;
+#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)
+ mod->refptr = percpu_modalloc(sizeof(local_t), __alignof__(local_t),
+ mod->name);
+ if (!mod->refptr) {
+ err = -ENOMEM;
+ goto free_init;
+ }
+#endif
/* Now we've moved module, initialize linked lists, etc. */
module_unload_init(mod);
@@ -2288,15 +2288,17 @@ static noinline struct module *load_module(void __user *umod,
ftrace_release(mod->module_core, mod->core_size);
free_unload:
module_unload_free(mod);
+ free_init:
+#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)
+ percpu_modfree(mod->refptr);
+#endif
module_free(mod, mod->module_init);
free_core:
module_free(mod, mod->module_core);
+ /* mod will be freed with core. Don't access it beyond this line! */
free_percpu:
if (percpu)
percpu_modfree(percpu);
-#if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)
- percpu_modfree(mod->refptr);
-#endif
free_mod:
kfree(args);
free_hdr:
--
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