[4/5] jfs: preserve i_mode if __jfs_set_acl() fails

Submitted by Ernesto A. Fernández on July 12, 2017, 9:55 a.m.

Details

Message ID fb576cd6fe08fb4dc61970442c529f1a3ab02b71.1499805488.git.ernesto.mnd.fernandez@gmail.com
State New
Headers show

Commit Message

Ernesto A. Fernández July 12, 2017, 9:55 a.m.
When changing a file's acl mask, __jfs_set_acl() will first set the group
bits of i_mode to the value of the mask, and only then set the actual
extended attribute representing the new acl.

If the second part fails (due to lack of space, for example) and the file
had no acl attribute to begin with, the system will from now on assume
that the mask permission bits are actual group permission bits, potentially
granting access to the wrong users.

Prevent this by only changing the inode mode after the acl has been set.

Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
---
 fs/jfs/acl.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

Comments

Dave Kleikamp July 13, 2017, 9:01 p.m.
On 07/12/2017 04:55 AM, Ernesto A. Fernández wrote:
> When changing a file's acl mask, __jfs_set_acl() will first set the group
> bits of i_mode to the value of the mask, and only then set the actual
> extended attribute representing the new acl.
> 
> If the second part fails (due to lack of space, for example) and the file
> had no acl attribute to begin with, the system will from now on assume
> that the mask permission bits are actual group permission bits, potentially
> granting access to the wrong users.
> 
> Prevent this by only changing the inode mode after the acl has been set.

This looks good to me. I'll add it to the jfs queue.

Thanks,
Shaggy

> 
> Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
> ---
>  fs/jfs/acl.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
> index 7bc186f..db5a385 100644
> --- a/fs/jfs/acl.c
> +++ b/fs/jfs/acl.c
> @@ -73,16 +73,17 @@ static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
>  	int rc;
>  	int size = 0;
>  	char *value = NULL;
> +	int update_mode = 0;
> +	umode_t mode = inode->i_mode;
>  
>  	switch (type) {
>  	case ACL_TYPE_ACCESS:
>  		ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
>  		if (acl) {
> -			rc = posix_acl_update_mode(inode, &inode->i_mode, &acl);
> +			rc = posix_acl_update_mode(inode, &mode, &acl);
>  			if (rc)
>  				return rc;
> -			inode->i_ctime = current_time(inode);
> -			mark_inode_dirty(inode);
> +			update_mode = 1;
>  		}
>  		break;
>  	case ACL_TYPE_DEFAULT:
> @@ -105,8 +106,14 @@ static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
>  out:
>  	kfree(value);
>  
> -	if (!rc)
> +	if (!rc) {
>  		set_cached_acl(inode, type, acl);
> +		if (update_mode) {
> +			inode->i_mode = mode;
> +			inode->i_ctime = current_time(inode);
> +			mark_inode_dirty(inode);
> +		}
> +	}
>  
>  	return rc;
>  }
>

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diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
index 7bc186f..db5a385 100644
--- a/fs/jfs/acl.c
+++ b/fs/jfs/acl.c
@@ -73,16 +73,17 @@  static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
 	int rc;
 	int size = 0;
 	char *value = NULL;
+	int update_mode = 0;
+	umode_t mode = inode->i_mode;
 
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
 		if (acl) {
-			rc = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+			rc = posix_acl_update_mode(inode, &mode, &acl);
 			if (rc)
 				return rc;
-			inode->i_ctime = current_time(inode);
-			mark_inode_dirty(inode);
+			update_mode = 1;
 		}
 		break;
 	case ACL_TYPE_DEFAULT:
@@ -105,8 +106,14 @@  static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
 out:
 	kfree(value);
 
-	if (!rc)
+	if (!rc) {
 		set_cached_acl(inode, type, acl);
+		if (update_mode) {
+			inode->i_mode = mode;
+			inode->i_ctime = current_time(inode);
+			mark_inode_dirty(inode);
+		}
+	}
 
 	return rc;
 }