module: Remove duplicate freeing of lockdep classes

[PATCH] module: Remove duplicate freeing of lockdep classes

Posted by Petr Pavlu 1 month ago

In the error path of load_module(), under the free_module label, the
code calls lockdep_free_key_range() to release lock classes associated
with the MOD_DATA, MOD_RODATA and MOD_RO_AFTER_INIT module regions, and
subsequently invokes module_deallocate().

Since commit ac3b43283923 ("module: replace module_layout with
module_memory"), the module_deallocate() function calls free_mod_mem(),
which releases the lock classes as well and considers all module
regions.

Attempting to free these classes twice is unnecessary. Remove the
redundant code in load_module().

Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
---
 kernel/module/main.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 710ee30b3bea..bcd259505c8b 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3544,12 +3544,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	mutex_unlock(&module_mutex);
  free_module:
 	mod_stat_bump_invalid(info, flags);
-	/* Free lock-classes; relies on the preceding sync_rcu() */
-	for_class_mod_mem_type(type, core_data) {
-		lockdep_free_key_range(mod->mem[type].base,
-				       mod->mem[type].size);
-	}
-
 	module_memory_restore_rox(mod);
 	module_deallocate(mod, info);
  free_copy:

base-commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c
-- 
2.52.0

Re: [PATCH] module: Remove duplicate freeing of lockdep classes

Posted by Aaron Tomlin 3 weeks, 4 days ago

On Wed, Jan 07, 2026 at 01:22:57PM +0100, Petr Pavlu wrote:
> In the error path of load_module(), under the free_module label, the
> code calls lockdep_free_key_range() to release lock classes associated
> with the MOD_DATA, MOD_RODATA and MOD_RO_AFTER_INIT module regions, and
> subsequently invokes module_deallocate().
> 
> Since commit ac3b43283923 ("module: replace module_layout with
> module_memory"), the module_deallocate() function calls free_mod_mem(),
> which releases the lock classes as well and considers all module
> regions.
> 
> Attempting to free these classes twice is unnecessary. Remove the
> redundant code in load_module().
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
> ---
>  kernel/module/main.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 710ee30b3bea..bcd259505c8b 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -3544,12 +3544,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	mutex_unlock(&module_mutex);
>   free_module:
>  	mod_stat_bump_invalid(info, flags);
> -	/* Free lock-classes; relies on the preceding sync_rcu() */
> -	for_class_mod_mem_type(type, core_data) {
> -		lockdep_free_key_range(mod->mem[type].base,
> -				       mod->mem[type].size);
> -	}
> -
>  	module_memory_restore_rox(mod);
>  	module_deallocate(mod, info);
>   free_copy:
> 
> base-commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c
> -- 
> 2.52.0
> 

Thank you!

Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>

-- 
Aaron Tomlin

Re: [PATCH] module: Remove duplicate freeing of lockdep classes

Posted by Song Liu 3 weeks, 4 days ago

On Wed, Jan 7, 2026 at 4:24 AM Petr Pavlu <petr.pavlu@suse.com> wrote:
>
> In the error path of load_module(), under the free_module label, the
> code calls lockdep_free_key_range() to release lock classes associated
> with the MOD_DATA, MOD_RODATA and MOD_RO_AFTER_INIT module regions, and
> subsequently invokes module_deallocate().
>
> Since commit ac3b43283923 ("module: replace module_layout with
> module_memory"), the module_deallocate() function calls free_mod_mem(),
> which releases the lock classes as well and considers all module
> regions.
>
> Attempting to free these classes twice is unnecessary. Remove the
> redundant code in load_module().
>
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

Acked-by: Song Liu <song@kernel.org>

Thanks for the fix!

Re: [PATCH] module: Remove duplicate freeing of lockdep classes

Posted by Peter Zijlstra 3 weeks, 4 days ago

On Wed, Jan 07, 2026 at 01:22:57PM +0100, Petr Pavlu wrote:
> In the error path of load_module(), under the free_module label, the
> code calls lockdep_free_key_range() to release lock classes associated
> with the MOD_DATA, MOD_RODATA and MOD_RO_AFTER_INIT module regions, and
> subsequently invokes module_deallocate().
> 
> Since commit ac3b43283923 ("module: replace module_layout with
> module_memory"), the module_deallocate() function calls free_mod_mem(),
> which releases the lock classes as well and considers all module
> regions.
> 
> Attempting to free these classes twice is unnecessary. Remove the
> redundant code in load_module().
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

Indeed,

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

> ---
>  kernel/module/main.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 710ee30b3bea..bcd259505c8b 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -3544,12 +3544,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	mutex_unlock(&module_mutex);
>   free_module:
>  	mod_stat_bump_invalid(info, flags);
> -	/* Free lock-classes; relies on the preceding sync_rcu() */
> -	for_class_mod_mem_type(type, core_data) {
> -		lockdep_free_key_range(mod->mem[type].base,
> -				       mod->mem[type].size);
> -	}
> -
>  	module_memory_restore_rox(mod);
>  	module_deallocate(mod, info);
>   free_copy:
> 
> base-commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c
> -- 
> 2.52.0
>

Re: [PATCH] module: Remove duplicate freeing of lockdep classes

Posted by Aaron Tomlin 1 month ago

On Wed, Jan 07, 2026 at 01:22:57PM +0100, Petr Pavlu wrote:
> In the error path of load_module(), under the free_module label, the
> code calls lockdep_free_key_range() to release lock classes associated
> with the MOD_DATA, MOD_RODATA and MOD_RO_AFTER_INIT module regions, and
> subsequently invokes module_deallocate().
> 
> Since commit ac3b43283923 ("module: replace module_layout with
> module_memory"), the module_deallocate() function calls free_mod_mem(),
> which releases the lock classes as well and considers all module
> regions.
> 
> Attempting to free these classes twice is unnecessary. Remove the
> redundant code in load_module().
> 
> Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
> ---
>  kernel/module/main.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 710ee30b3bea..bcd259505c8b 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -3544,12 +3544,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  	mutex_unlock(&module_mutex);
>   free_module:
>  	mod_stat_bump_invalid(info, flags);
> -	/* Free lock-classes; relies on the preceding sync_rcu() */
> -	for_class_mod_mem_type(type, core_data) {
> -		lockdep_free_key_range(mod->mem[type].base,
> -				       mod->mem[type].size);
> -	}
> -
>  	module_memory_restore_rox(mod);
>  	module_deallocate(mod, info);
>   free_copy:
> 
> base-commit: 3609fa95fb0f2c1b099e69e56634edb8fc03f87c
> -- 
> 2.52.0
> 

Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>

-- 
Aaron Tomlin