On Thu, Nov 21, 2019 at 9:52 AM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
> commit bda0be7ad994 ("security: make inode_follow_link RCU-walk aware")
> passed down the rcu flag to the SELinux AVC, but failed to adjust the
> test in slow_avc_audit() to also return -ECHILD on LSM_AUDIT_DATA_DENTRY.
> Previously, we only returned -ECHILD if generating an audit record with
> LSM_AUDIT_DATA_INODE since this was only relevant from inode_permission.
> Return -ECHILD on either LSM_AUDIT_DATA_INODE or LSM_AUDIT_DATA_DENTRY.
> LSM_AUDIT_DATA_INODE only requires this handling due to the fact
> that dump_common_audit_data() calls d_find_alias() and collects the
> dname from the result if any.
> Other cases that might require similar treatment in the future are
> LSM_AUDIT_DATA_PATH and LSM_AUDIT_DATA_FILE if any hook that takes
> a path or file is called under RCU-walk.
>
> Fixes: bda0be7ad994 ("security: make inode_follow_link RCU-walk aware")
> Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx>
> ---
> security/selinux/avc.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/security/selinux/avc.c b/security/selinux/avc.c
> index 74c43ebe34bb..f1fa1072230c 100644
> --- a/security/selinux/avc.c
> +++ b/security/selinux/avc.c
> @@ -779,7 +779,8 @@ noinline int slow_avc_audit(struct selinux_state *state,
> * during retry. However this is logically just as if the operation
> * happened a little later.
> */
> - if ((a->type == LSM_AUDIT_DATA_INODE) &&
> + if ((a->type == LSM_AUDIT_DATA_INODE ||
> + a->type == LSM_AUDIT_DATA_DENTRY) &&
> (flags & MAY_NOT_BLOCK))
> return -ECHILD;
Added the LSM list as I'm beginning to wonder if we should push this
logic down into common_lsm_audit(), this problem around blocking
shouldn't be SELinux specific.
For the LSM folks just joining, the full patchset can be found here:
* https://lore.kernel.org/selinux/20191121145245.8637-1-sds@xxxxxxxxxxxxx/T/#t
--
paul moore
www.paul-moore.com
