On Tue, Jul 05, 2016 at 05:32:30PM -0400, jeffm@xxxxxxxx wrote:
> From: Jeff Mahoney <jeffm@xxxxxxxx>
>
> There are legitimate reasons to disallow mmap on certain files, notably
> in sysfs or procfs. We shouldn't emulate mmap support on file systems
> that don't offer support natively.
>
> Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
> ---
> fs/ecryptfs/file.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
> index 7000b96..4aaa656 100644
> --- a/fs/ecryptfs/file.c
> +++ b/fs/ecryptfs/file.c
> @@ -169,6 +169,20 @@ out:
> return rc;
> }
>
> +
> +static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> + struct dentry *dentry = ecryptfs_dentry_to_lower(file_dentry(file));
> + /*
> + * Don't allow mmap on top of file systems that don't support it
> + * natively. If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
> + * allows recursive mounting, this will need to be extended.
Or if another new stacking filesystem appears whose f_op->mmap just forwards
to lower_f_op->mmap - but thinking about it, in that scenario, my patch
would stop working, too.
At this point, I dislike both this patch and my own one because of their
lack of robustness. Well, at least e54ad7f1ee263ffa5a2de9c609d58dfa27b21cd9
should be solid. :/
> + */
> + if (!d_inode(dentry)->i_fop->mmap)
> + return -ENODEV;
> + return generic_file_mmap(file, vma);
> +}
> +
> /**
> * ecryptfs_open
> * @inode: inode speciying file to open
> @@ -403,7 +417,7 @@ const struct file_operations ecryptfs_main_fops = {
> #ifdef CONFIG_COMPAT
> .compat_ioctl = ecryptfs_compat_ioctl,
> #endif
> - .mmap = generic_file_mmap,
> + .mmap = ecryptfs_mmap,
> .open = ecryptfs_open,
> .flush = ecryptfs_flush,
> .release = ecryptfs_release,
> --
> 2.7.1
>
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