On Fri, Jul 14, 2023 at 11:26 PM Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx> wrote: > On Sat, Jul 08, 2023 at 12:23:04AM -0400, Paul Moore wrote: > > On Jun 28, 2023 Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > As is typical with LSMs, IPE uses securityfs as its interface with > > > userspace. for a complete list of the interfaces and the respective > > > inputs/outputs, please see the documentation under > > > admin-guide/LSM/ipe.rst > > > > > > Signed-off-by: Deven Bowers <deven.desai@xxxxxxxxxxxxxxxxxxx> > > > Signed-off-by: Fan Wu <wufan@xxxxxxxxxxxxxxxxxxx> > > > --- > > > security/ipe/Makefile | 2 + > > > security/ipe/fs.c | 101 ++++++++ > > > security/ipe/fs.h | 16 ++ > > > security/ipe/ipe.c | 3 + > > > security/ipe/ipe.h | 2 + > > > security/ipe/policy.c | 111 +++++++++ > > > security/ipe/policy.h | 9 + > > > security/ipe/policy_fs.c | 481 +++++++++++++++++++++++++++++++++++++++ > > > 8 files changed, 725 insertions(+) > > > create mode 100644 security/ipe/fs.c > > > create mode 100644 security/ipe/fs.h > > > create mode 100644 security/ipe/policy_fs.c ... > > > @@ -39,6 +67,65 @@ static int set_pkcs7_data(void *ctx, const void *data, size_t len, > > > return 0; > > > } > > > > > > +/** > > > + * ipe_update_policy - parse a new policy and replace @old with it. > > > > What does "@old" refer to? I'm guessing you want to drop the "@". > > > Yes it shouldn't be here, sorry confusion. > > > > + * @root: Supplies a pointer to the securityfs inode saved the policy. > > > + * @text: Supplies a pointer to the plain text policy. > > > + * @textlen: Supplies the length of @text. > > > + * @pkcs7: Supplies a pointer to a buffer containing a pkcs7 message. > > > + * @pkcs7len: Supplies the length of @pkcs7len. > > > + * > > > + * @text/@textlen is mutually exclusive with @pkcs7/@pkcs7len - see > > > + * ipe_new_policy. > > > + * > > > + * Return: > > > + * * !IS_ERR - The old policy > > > > "The old policy" is what? > > > Let me try to pharse it in another way, how about the existing policy > saved in the inode before update? That sounds better, thanks. > > > diff --git a/security/ipe/policy_fs.c b/security/ipe/policy_fs.c > > > new file mode 100644 > > > index 000000000000..52a120118cda > > > --- /dev/null > > > +++ b/security/ipe/policy_fs.c > > > @@ -0,0 +1,481 @@ > > > > ... > > > > > +/** > > > + * getactive - Read handler for "ipe/policies/$name/active". > > > + * @f: Supplies a file structure representing the securityfs node. > > > + * @data: Suppleis a buffer passed to the write syscall. > > > + * @len: Supplies the length of @data. > > > + * @offset: unused. > > > + * > > > + * @data will be populated with the 1 or 0 depending on if the > > > + * corresponding policy is active. > > > + * > > > + * Return: > > > + * * >0 - Success, Length of buffer written > > > + * * <0 - Error > > > + */ > > > +static ssize_t getactive(struct file *f, char __user *data, > > > + size_t len, loff_t *offset) > > > +{ > > > + int rc = 0; > > > + const char *str; > > > + struct inode *root = NULL; > > > + const struct ipe_policy *p = NULL; > > > + > > > + root = d_inode(f->f_path.dentry->d_parent); > > > + > > > + inode_lock_shared(root); > > > + p = (struct ipe_policy *)root->i_private; > > > + if (!p) { > > > + inode_unlock_shared(root); > > > + return -ENOENT; > > > + } > > > + inode_unlock_shared(root); > > > + > > > + str = (p == rcu_access_pointer(ipe_active_policy)) ? "1" : "0"; > > > > The line above should be wrapped with a RCU lock. > > This call only checks the value inside the pointer but doesn't dereference it. > Also from https://lwn.net/Articles/652156/ I found it says "The call to > rcu_access_pointer() need not be protected. In contrast, rcu_dereference() must > either be within an RCU read-side critical section", so I didn't add the lock > here, is this article outdated? No, I believe you are correct. There is always something new to learn with RCU, thanks ;) -- paul-moore.com