configfs: fix a race in configfs_lookup() in stable-5.10.y

[PATCH] configfs: fix a race in configfs_lookup() in stable-5.10.y

Posted by Kyle Zeng 2 years, 3 months ago

Basically porting c42dd069be8dfc9b2239a5c89e73bbd08ab35de0 to
stable-v5.10.y to avoid race condition between configfs_dir_lseek and
configfs_lookup since they both operate ->s_childre and configfs_lookup
forgets to obtain the lock.

Signed-off-by: Kyle Zeng <zengyhkyle@gmail.com>
---
 fs/configfs/dir.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 12388ed4faa5..0b7e9ab517d5 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -479,6 +479,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
 	if (!configfs_dirent_is_ready(parent_sd))
 		goto out;
 
+	spin_lock(&configfs_dirent_lock);
 	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
 		if (sd->s_type & CONFIGFS_NOT_PINNED) {
 			const unsigned char * name = configfs_get_name(sd);
@@ -491,6 +492,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
 			break;
 		}
 	}
+	spin_unlock(&configfs_dirent_lock);
 
 	if (!found) {
 		/*
-- 
2.34.1

Re: [PATCH] configfs: fix a race in configfs_lookup() in stable-5.10.y

Posted by Greg KH 2 years, 3 months ago

On Fri, Sep 01, 2023 at 05:50:37PM -0700, Kyle Zeng wrote:
> Basically porting c42dd069be8dfc9b2239a5c89e73bbd08ab35de0 to
> stable-v5.10.y to avoid race condition between configfs_dir_lseek and
> configfs_lookup since they both operate ->s_childre and configfs_lookup
> forgets to obtain the lock.
> 
> Signed-off-by: Kyle Zeng <zengyhkyle@gmail.com>
> ---
>  fs/configfs/dir.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 12388ed4faa5..0b7e9ab517d5 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -479,6 +479,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
>  	if (!configfs_dirent_is_ready(parent_sd))
>  		goto out;
>  
> +	spin_lock(&configfs_dirent_lock);
>  	list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
>  		if (sd->s_type & CONFIGFS_NOT_PINNED) {
>  			const unsigned char * name = configfs_get_name(sd);
> @@ -491,6 +492,7 @@ static struct dentry * configfs_lookup(struct inode *dir,
>  			break;
>  		}
>  	}
> +	spin_unlock(&configfs_dirent_lock);
>  
>  	if (!found) {
>  		/*
> -- 
> 2.34.1
> 

<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>