Re: [Jfs-discussion] [PATCH 1/5] ext4: preserve i_mode if __ext4_set_acl() fails

2017-07-30 Thread Theodore Ts'o
On Wed, Jul 12, 2017 at 06:53:51AM -0300, Ernesto A. Fernández wrote:
> When changing a file's acl mask, __ext4_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 

Thanks, applied.

- Ted

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Re: [Jfs-discussion] [PATCH 1/5] ext4: preserve i_mode if __ext4_set_acl() fails

2017-07-17 Thread Jan Kara
On Wed 12-07-17 06:53:51, Ernesto A. Fernández wrote:
> When changing a file's acl mask, __ext4_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 

This clashes with my fix of another bug in that area [1] but the fixup
should be straightforward. The patch looks good to me so feel free to add

Reviewed-by: Jan Kara 

[1] https://www.spinics.net/lists/stable/msg178111.html

Honza

> ---
>  fs/ext4/acl.c | 15 +++
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
> index 09441ae..2985cd0 100644
> --- a/fs/ext4/acl.c
> +++ b/fs/ext4/acl.c
> @@ -189,16 +189,17 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, 
> int type,
>   void *value = NULL;
>   size_t size = 0;
>   int error;
> + int update_mode = 0;
> + umode_t mode = inode->i_mode;
>  
>   switch (type) {
>   case ACL_TYPE_ACCESS:
>   name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
>   if (acl) {
> - error = posix_acl_update_mode(inode, >i_mode, 
> );
> + error = posix_acl_update_mode(inode, , );
>   if (error)
>   return error;
> - inode->i_ctime = current_time(inode);
> - ext4_mark_inode_dirty(handle, inode);
> + update_mode = 1;
>   }
>   break;
>  
> @@ -221,8 +222,14 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, 
> int type,
> value, size, xattr_flags);
>  
>   kfree(value);
> - if (!error)
> + if (!error) {
>   set_cached_acl(inode, type, acl);
> + if (update_mode) {
> + inode->i_mode = mode;
> + inode->i_ctime = current_time(inode);
> + ext4_mark_inode_dirty(handle, inode);
> + }
> + }
>  
>   return error;
>  }
> -- 
> 2.1.4
> 
> 
-- 
Jan Kara 
SUSE Labs, CR

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