These ioctls are equivalent to fcntl(fd, F_SETFD, flags), which SELinux
always allows too. Furthermore, a failed FIOCLEX could result in a file
descriptor being leaked to a process that should not have access to it.
As this patch removes access controls, a policy capability needs to be
enabled in policy to always allow these ioctls.
Based-on-patch-by: Demi Marie Obenour <[email protected]>
Signed-off-by: Richard Haines <[email protected]>
---
V2 Change: Control via a policy capability.
V3 Change: Update switch check.
security/selinux/hooks.c | 6 ++++++
security/selinux/include/policycap.h | 1 +
security/selinux/include/policycap_names.h | 3 ++-
security/selinux/include/security.h | 7 +++++++
4 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5b6895e4f..d369c2d82 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3745,6 +3745,12 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
CAP_OPT_NONE, true);
break;
+ case FIOCLEX:
+ case FIONCLEX:
+ if (!selinux_policycap_ioctl_skip_cloexec())
+ error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd);
+ break;
+
/* default case assumes that the command will go
* to the file's ioctl() function.
*/
diff --git a/security/selinux/include/policycap.h b/security/selinux/include/policycap.h
index 2ec038efb..44d73dc32 100644
--- a/security/selinux/include/policycap.h
+++ b/security/selinux/include/policycap.h
@@ -11,6 +11,7 @@ enum {
POLICYDB_CAPABILITY_CGROUPSECLABEL,
POLICYDB_CAPABILITY_NNP_NOSUID_TRANSITION,
POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS,
+ POLICYDB_CAPABILITY_IOCTL_CLOEXEC,
__POLICYDB_CAPABILITY_MAX
};
#define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
diff --git a/security/selinux/include/policycap_names.h b/security/selinux/include/policycap_names.h
index b89289f09..ebd64afe1 100644
--- a/security/selinux/include/policycap_names.h
+++ b/security/selinux/include/policycap_names.h
@@ -12,7 +12,8 @@ const char *selinux_policycap_names[__POLICYDB_CAPABILITY_MAX] = {
"always_check_network",
"cgroup_seclabel",
"nnp_nosuid_transition",
- "genfs_seclabel_symlinks"
+ "genfs_seclabel_symlinks",
+ "ioctl_skip_cloexec"
};
#endif /* _SELINUX_POLICYCAP_NAMES_H_ */
diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
index ac0ece013..8a789c22b 100644
--- a/security/selinux/include/security.h
+++ b/security/selinux/include/security.h
@@ -219,6 +219,13 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS]);
}
+static inline bool selinux_policycap_ioctl_skip_cloexec(void)
+{
+ struct selinux_state *state = &selinux_state;
+
+ return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_IOCTL_CLOEXEC]);
+}
+
struct selinux_policy_convert_data;
struct selinux_load_state {
--
2.35.1
On Thu, Feb 24, 2022 at 5:24 AM Richard Haines
<[email protected]> wrote:
>
> These ioctls are equivalent to fcntl(fd, F_SETFD, flags), which SELinux
> always allows too. Furthermore, a failed FIOCLEX could result in a file
> descriptor being leaked to a process that should not have access to it.
>
> As this patch removes access controls, a policy capability needs to be
> enabled in policy to always allow these ioctls.
>
> Based-on-patch-by: Demi Marie Obenour <[email protected]>
> Signed-off-by: Richard Haines <[email protected]>
> ---
> V2 Change: Control via a policy capability.
> V3 Change: Update switch check.
>
> security/selinux/hooks.c | 6 ++++++
> security/selinux/include/policycap.h | 1 +
> security/selinux/include/policycap_names.h | 3 ++-
> security/selinux/include/security.h | 7 +++++++
> 4 files changed, 16 insertions(+), 1 deletion(-)
This looks good to me, but before I merge this are the SELinux
userspace folks okay with the policy capability's name and enum value?
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 5b6895e4f..d369c2d82 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3745,6 +3745,12 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
> CAP_OPT_NONE, true);
> break;
>
> + case FIOCLEX:
> + case FIONCLEX:
> + if (!selinux_policycap_ioctl_skip_cloexec())
> + error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd);
> + break;
> +
> /* default case assumes that the command will go
> * to the file's ioctl() function.
> */
> diff --git a/security/selinux/include/policycap.h b/security/selinux/include/policycap.h
> index 2ec038efb..44d73dc32 100644
> --- a/security/selinux/include/policycap.h
> +++ b/security/selinux/include/policycap.h
> @@ -11,6 +11,7 @@ enum {
> POLICYDB_CAPABILITY_CGROUPSECLABEL,
> POLICYDB_CAPABILITY_NNP_NOSUID_TRANSITION,
> POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS,
> + POLICYDB_CAPABILITY_IOCTL_CLOEXEC,
> __POLICYDB_CAPABILITY_MAX
> };
> #define POLICYDB_CAPABILITY_MAX (__POLICYDB_CAPABILITY_MAX - 1)
> diff --git a/security/selinux/include/policycap_names.h b/security/selinux/include/policycap_names.h
> index b89289f09..ebd64afe1 100644
> --- a/security/selinux/include/policycap_names.h
> +++ b/security/selinux/include/policycap_names.h
> @@ -12,7 +12,8 @@ const char *selinux_policycap_names[__POLICYDB_CAPABILITY_MAX] = {
> "always_check_network",
> "cgroup_seclabel",
> "nnp_nosuid_transition",
> - "genfs_seclabel_symlinks"
> + "genfs_seclabel_symlinks",
> + "ioctl_skip_cloexec"
> };
>
> #endif /* _SELINUX_POLICYCAP_NAMES_H_ */
> diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h
> index ac0ece013..8a789c22b 100644
> --- a/security/selinux/include/security.h
> +++ b/security/selinux/include/security.h
> @@ -219,6 +219,13 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void)
> return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS]);
> }
>
> +static inline bool selinux_policycap_ioctl_skip_cloexec(void)
> +{
> + struct selinux_state *state = &selinux_state;
> +
> + return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_IOCTL_CLOEXEC]);
> +}
> +
> struct selinux_policy_convert_data;
>
> struct selinux_load_state {
> --
> 2.35.1
--
paul-moore.com
On Fri, Feb 25, 2022 at 1:34 AM Paul Moore <[email protected]> wrote:
> On Thu, Feb 24, 2022 at 5:24 AM Richard Haines
> <[email protected]> wrote:
> >
> > These ioctls are equivalent to fcntl(fd, F_SETFD, flags), which SELinux
> > always allows too. Furthermore, a failed FIOCLEX could result in a file
> > descriptor being leaked to a process that should not have access to it.
> >
> > As this patch removes access controls, a policy capability needs to be
> > enabled in policy to always allow these ioctls.
> >
> > Based-on-patch-by: Demi Marie Obenour <[email protected]>
> > Signed-off-by: Richard Haines <[email protected]>
> > ---
> > V2 Change: Control via a policy capability.
> > V3 Change: Update switch check.
> >
> > security/selinux/hooks.c | 6 ++++++
> > security/selinux/include/policycap.h | 1 +
> > security/selinux/include/policycap_names.h | 3 ++-
> > security/selinux/include/security.h | 7 +++++++
> > 4 files changed, 16 insertions(+), 1 deletion(-)
>
> This looks good to me, but before I merge this are the SELinux
> userspace folks okay with the policy capability's name and enum value?
Since you mention it... I would suggest naming the enum
POLICYDB_CAPABILITY_IOCTL_SKIP_CLOEXEC to match the display name. Yes,
it becomes awkwardly long, but e.g.
POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS is already longer than
that, so I'd prefer more descriptiveness over brevity.
(IMHO the POLICYDB_CAPABILITY_ prefix is ridiculously long for no
reason and we should simply shorten it (just POLCAP_ would be
perfectly fine, IMHO) instead of trying to abbreviate the rest. Of
course, this doesn't have to be done now - I'm taking a note to myself
to splice in such rename next time I add a new capability, if not
earlier.)
--
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.
On Fri, Feb 25, 2022 at 5:02 AM Ondrej Mosnacek <[email protected]> wrote:
> (IMHO the POLICYDB_CAPABILITY_ prefix is ridiculously long for no
> reason and we should simply shorten it (just POLCAP_ would be
> perfectly fine, IMHO) instead of trying to abbreviate the rest. Of
> course, this doesn't have to be done now - I'm taking a note to myself
> to splice in such rename next time I add a new capability, if not
> earlier.)
Yeah, that prefix is probably longer than it needs to be. Since we're
at -rc5 right now, with -rc6 just a few days away, I'll go ahead and
toss out a patch to shorten the names next week. While I have very
mixed feelings on style/formatting-only patches, things like this
should go into selinux/next at the end of the -rcX cycle so as not to
cause unnecessary conflicts for people making "real" changes :)
--
paul-moore.com