[PATCH] ia64:unwind: fix double free for mod->arch.init_unw_table

[PATCH] ia64:unwind: fix double free for mod->arch.init_unw_table

[chenzefeng]

The function free_module in file kernel/module.c as follow:

void free_module(struct module *mod) {
	......
	module_arch_cleanup(mod);
	......
	module_arch_freeing_init(mod);
	......
}

Both module_arch_cleanup and module_arch_freeing_init function
would free the mod->arch.init_unw_table, which cause double free.

Here, set mod->arch.init_unw_table = NULL after remove the unwind
table to avoid double free.

Signed-off-by: chenzefeng <chenzefeng2@huawei.com>
---
 arch/ia64/kernel/module.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index 326448f..1a42ba8 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -914,10 +914,14 @@ struct plt_entry {
 void
 module_arch_cleanup (struct module *mod)
 {
-	if (mod->arch.init_unw_table)
+	if (mod->arch.init_unw_table) {
 		unw_remove_unwind_table(mod->arch.init_unw_table);
-	if (mod->arch.core_unw_table)
+		mod->arch.init_unw_table = NULL;
+	}
+	if (mod->arch.core_unw_table) {
 		unw_remove_unwind_table(mod->arch.core_unw_table);
+		mod->arch.core_unw_table = NULL;
+	}
 }
 
 void *dereference_module_function_descriptor(struct module *mod, void *ptr)
-- 
1.8.5.6

Re: [PATCH] ia64:unwind: fix double free for mod->arch.init_unw_table

[Greg KH]

On Tue, Aug 06, 2019 at 03:46:33PM +0800, chenzefeng wrote:
> The function free_module in file kernel/module.c as follow:
> 
> void free_module(struct module *mod) {
> 	......
> 	module_arch_cleanup(mod);
> 	......
> 	module_arch_freeing_init(mod);
> 	......
> }
> 
> Both module_arch_cleanup and module_arch_freeing_init function
> would free the mod->arch.init_unw_table, which cause double free.
> 
> Here, set mod->arch.init_unw_table = NULL after remove the unwind
> table to avoid double free.
> 
> Signed-off-by: chenzefeng <chenzefeng2@huawei.com>
> ---
>  arch/ia64/kernel/module.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

RE: [PATCH] ia64:unwind: fix double free for mod->arch.init_unw_table

[Luck, Tony]

> Here, set mod->arch.init_unw_table = NULL after remove the unwind
> table to avoid double free.

Applied. Thanks.

-Tony