[PATCH] locks: fix a memory leak bug

[PATCH] locks: fix a memory leak bug

[Wenwen Wang]

In __break_lease(), the file lock 'new_fl' is allocated in lease_alloc().
However, it is not deallocated in the following execution if
smp_load_acquire() fails, leading to a memory leak bug. To fix this issue,
free 'new_fl' before returning the error.

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
---
 fs/locks.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/locks.c b/fs/locks.c
index 686eae2..5993b2a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1592,7 +1592,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 	ctx = smp_load_acquire(&inode->i_flctx);
 	if (!ctx) {
 		WARN_ON_ONCE(1);
-		return error;
+		goto free_lock;
 	}
 
 	percpu_down_read(&file_rwsem);
@@ -1672,6 +1672,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 	spin_unlock(&ctx->flc_lock);
 	percpu_up_read(&file_rwsem);
 	locks_dispose_list(&dispose);
+free_lock:
 	locks_free_lock(new_fl);
 	return error;
 }
-- 
2.7.4

Re: [PATCH] locks: fix a memory leak bug

[Jeff Layton]

On Mon, 2019-08-19 at 18:47 -0500, Wenwen Wang wrote:
> In __break_lease(), the file lock 'new_fl' is allocated in lease_alloc().
> However, it is not deallocated in the following execution if
> smp_load_acquire() fails, leading to a memory leak bug. To fix this issue,
> free 'new_fl' before returning the error.
> 
> Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
> ---
>  fs/locks.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 686eae2..5993b2a 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -1592,7 +1592,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
>  	ctx = smp_load_acquire(&inode->i_flctx);
>  	if (!ctx) {
>  		WARN_ON_ONCE(1);
> -		return error;
> +		goto free_lock;
>  	}
>  
>  	percpu_down_read(&file_rwsem);
> @@ -1672,6 +1672,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
>  	spin_unlock(&ctx->flc_lock);
>  	percpu_up_read(&file_rwsem);
>  	locks_dispose_list(&dispose);
> +free_lock:
>  	locks_free_lock(new_fl);
>  	return error;
>  }

Good catch! Merged for v5.4. Let me know if you think this needs to go
in earlier and/or to stable kernels.

Thanks,
-- 
Jeff Layton <jlayton@kernel.org>