linux-ext4 - Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sun, 9 Jun 2019 21:51:45 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/8] mm/fs: don't allow writes to immutable files

On Wed, Apr 17, 2019 at 12:04:33PM -0700, Darrick J. Wong wrote:
> diff --git a/mm/memory.c b/mm/memory.c
> index ab650c21bccd..dfd5eba278d6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2149,6 +2149,9 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
>  
>  	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
>  
> +	if (vmf->vma->vm_file && IS_IMMUTABLE(file_inode(vmf->vma->vm_file)))
> +		return VM_FAULT_SIGBUS;
> +
>  	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
>  	/* Restore original flags so that caller is not surprised */
>  	vmf->flags = old_flags;

Shouldn't this check be moved before the modification of vmf->flags?
It looks like do_page_mkwrite() isn't supposed to be returning with
vmf->flags modified, lest "the caller gets surprised".

	   	     	       	      	   - Ted