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Date: Thu, 14 May 2015 11:09:25 -0400
From: bfields@...ldses.org (J. Bruce Fields)
To: Andreas Gruenbacher <andreas.gruenbacher@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-nfs@...r.kernel.org
Subject: Re: [RFC v3 20/45] richacl: Automatic Inheritance
Looks fine to me.
>From a quick check of
git://github.com/andreas-gruenbacher/richacl.git
it looks like the userspace is all done too?
Do we have wireshark patches?
On Fri, Apr 24, 2015 at 01:04:17PM +0200, Andreas Gruenbacher wrote:
> Automatic Inheritance (AI) allows changes to the acl of a directory to
> recursively propagate down to files and directories in the directory.
>
> To implement this, the kernel keeps track of which permissions have been
> inherited, and makes sure that permission propagation is turned off when the
> file permission bits of a file are changed (upon create or chmod).
>
> The actual permission propagation is implemented in user space.
Nit, but: I'd find a way to really emphasize this and put it in the very
first sentence of the changelog and any documentation. People keep
missing it.
--b.
>
> Automatic Inheritance works as follows:
>
> - When the ACL4_AUTO_INHERIT flag in the acl of a file is not set, the
> file is not affected by AI.
>
> - When the ACL4_AUTO_INHERIT flag in the acl of a directory is set and
> a file or subdirectory is created in that directory, files created in
> the directory will have the ACL4_AUTO_INHERIT flag set, and all
> inherited aces will have the ACE4_INHERITED_ACE flag set. This
> allows user space to distinguish between aces which have been
> inherited and aces which have been explicitly added.
>
> - When the ACL4_PROTECTED acl flag in the acl of a file is set, AI will
> not modify the acl of the file. This does not affect propagation of
> permissions from the file to its children (if the file is a
> directory).
>
> Linux does not have a way of creating files without setting the file permission
> bits, so all files created inside a directory with ACL4_AUTO_INHERIT set will
> also have the ACL4_PROTECTED flag set. This effectively disables Automatic
> Inheritance.
>
> Protocols which support creating files without specifying permissions can
> explicitly clear the ACL4_PROTECTED flag after creating a file and reset the
> file masks to "undo" applying the create mode; see richacl_compute_max_masks().
> This is a workaround; a mechanism that would allow a process to indicate to the
> kernel to ignore the create mode when there are inherited permissions would fix
> this problem.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
> ---
> fs/richacl_base.c | 10 +++++++++-
> fs/richacl_inode.c | 7 ++++++-
> include/linux/richacl.h | 25 +++++++++++++++++++++++--
> 3 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/fs/richacl_base.c b/fs/richacl_base.c
> index 54cb482..572f1b8 100644
> --- a/fs/richacl_base.c
> +++ b/fs/richacl_base.c
> @@ -352,7 +352,8 @@ richacl_chmod(struct richacl *acl, mode_t mode)
> if (acl->a_owner_mask == owner_mask &&
> acl->a_group_mask == group_mask &&
> acl->a_other_mask == other_mask &&
> - (acl->a_flags & RICHACL_MASKED))
> + (acl->a_flags & RICHACL_MASKED) &&
> + (!richacl_is_auto_inherit(acl) || richacl_is_protected(acl)))
> return acl;
>
> clone = richacl_clone(acl, GFP_KERNEL);
> @@ -364,6 +365,8 @@ richacl_chmod(struct richacl *acl, mode_t mode)
> clone->a_owner_mask = owner_mask;
> clone->a_group_mask = group_mask;
> clone->a_other_mask = other_mask;
> + if (richacl_is_auto_inherit(clone))
> + clone->a_flags |= RICHACL_PROTECTED;
>
> return clone;
> }
> @@ -434,6 +437,11 @@ richacl_inherit(const struct richacl *dir_acl, int isdir)
> ace++;
> }
> }
> + if (richacl_is_auto_inherit(dir_acl)) {
> + acl->a_flags = RICHACL_AUTO_INHERIT;
> + richacl_for_each_entry(ace, acl)
> + ace->e_flags |= RICHACE_INHERITED_ACE;
> + }
>
> return acl;
> }
> diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c
> index 1a5b868..dfbb15a 100644
> --- a/fs/richacl_inode.c
> +++ b/fs/richacl_inode.c
> @@ -223,9 +223,14 @@ richacl_inherit_inode(const struct richacl *dir_acl, struct inode *inode)
>
> acl = richacl_inherit(dir_acl, S_ISDIR(inode->i_mode));
> if (acl) {
> + /*
> + * We need to set RICHACL_PROTECTED because we are
> + * doing an implicit chmod
> + */
> + if (richacl_is_auto_inherit(acl))
> + acl->a_flags |= RICHACL_PROTECTED;
>
> richacl_compute_max_masks(acl);
> -
> /*
> * Ensure that the acl will not grant any permissions beyond
> * the create mode.
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index 8a92b89..bcc2b64 100644
> --- a/include/linux/richacl.h
> +++ b/include/linux/richacl.h
> @@ -53,9 +53,15 @@ struct richacl {
> _ace--)
>
> /* a_flag values */
> +#define RICHACL_AUTO_INHERIT 0x01
> +#define RICHACL_PROTECTED 0x02
> +#define RICHACL_DEFAULTED 0x04
> #define RICHACL_MASKED 0x80
>
> -#define RICHACL_VALID_FLAGS ( \
> +#define RICHACL_VALID_FLAGS ( \
> + RICHACL_AUTO_INHERIT | \
> + RICHACL_PROTECTED | \
> + RICHACL_DEFAULTED | \
> RICHACL_MASKED)
>
> /* e_type values */
> @@ -68,6 +74,7 @@ struct richacl {
> #define RICHACE_NO_PROPAGATE_INHERIT_ACE 0x0004
> #define RICHACE_INHERIT_ONLY_ACE 0x0008
> #define RICHACE_IDENTIFIER_GROUP 0x0040
> +#define RICHACE_INHERITED_ACE 0x0080
> #define RICHACE_SPECIAL_WHO 0x4000
>
> #define RICHACE_VALID_FLAGS ( \
> @@ -76,6 +83,7 @@ struct richacl {
> RICHACE_NO_PROPAGATE_INHERIT_ACE | \
> RICHACE_INHERIT_ONLY_ACE | \
> RICHACE_IDENTIFIER_GROUP | \
> + RICHACE_INHERITED_ACE | \
> RICHACE_SPECIAL_WHO)
>
> /* e_mask bitflags */
> @@ -187,6 +195,18 @@ extern void set_cached_richacl(struct inode *, struct richacl *);
> extern void forget_cached_richacl(struct inode *);
> extern struct richacl *get_richacl(struct inode *);
>
> +static inline int
> +richacl_is_auto_inherit(const struct richacl *acl)
> +{
> + return acl->a_flags & RICHACL_AUTO_INHERIT;
> +}
> +
> +static inline int
> +richacl_is_protected(const struct richacl *acl)
> +{
> + return acl->a_flags & RICHACL_PROTECTED;
> +}
> +
> /**
> * richace_is_owner - check if @ace is an OWNER@ entry
> */
> @@ -257,7 +277,8 @@ richace_clear_inheritance_flags(struct richace *ace)
> ace->e_flags &= ~(RICHACE_FILE_INHERIT_ACE |
> RICHACE_DIRECTORY_INHERIT_ACE |
> RICHACE_NO_PROPAGATE_INHERIT_ACE |
> - RICHACE_INHERIT_ONLY_ACE);
> + RICHACE_INHERIT_ONLY_ACE |
> + RICHACE_INHERITED_ACE);
> }
>
> /**
> --
> 2.1.0
>
> --
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