| Message ID | 20210202162710.657398-2-mic@digikod.net |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Landlock LSM | expand |
On Tue, Feb 02, 2021 at 05:26:59PM +0100, Mickaël Salaün wrote: > From: Mickaël Salaün <mic@linux.microsoft.com> > > A Landlock object enables to identify a kernel object (e.g. an inode). > A Landlock rule is a set of access rights allowed on an object. Rules > are grouped in rulesets that may be tied to a set of processes (i.e. > subjects) to enforce a scoped access-control (i.e. a domain). > > Because Landlock's goal is to empower any process (especially > unprivileged ones) to sandbox themselves, we cannot rely on a > system-wide object identification such as file extended attributes. > Indeed, we need innocuous, composable and modular access-controls. > > The main challenge with these constraints is to identify kernel objects > while this identification is useful (i.e. when a security policy makes > use of this object). But this identification data should be freed once > no policy is using it. This ephemeral tagging should not and may not be > written in the filesystem. We then need to manage the lifetime of a > rule according to the lifetime of its objects. To avoid a global lock, > this implementation make use of RCU and counters to safely reference > objects. > > A following commit uses this generic object management for inodes. > > Cc: James Morris <jmorris@namei.org> > Cc: Kees Cook <keescook@chromium.org> > Cc: Serge E. Hallyn <serge@hallyn.com> Acked-by: Serge Hallyn <serge@hallyn.com> Just a few suggestions for the description below. > Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> > Reviewed-by: Jann Horn <jannh@google.com> > --- > > Changes since v27: > * Update Kconfig for landlock_restrict_self(2). > * Cosmetic fixes: use 80 columns in Kconfig and align Makefile > declarations. > > Changes since v26: > * Update Kconfig for landlock_enforce_ruleset_self(2). > * Fix spelling. > > Changes since v24: > * Fix typo in comment (spotted by Jann Horn). > * Add Reviewed-by: Jann Horn <jannh@google.com> > > Changes since v23: > * Update landlock_create_object() to return error codes instead of NULL. > This help error handling in callers. > * When using make oldconfig with a previous configuration already > including the CONFIG_LSM variable, no question is asked to update its > content. Update the Kconfig help to warn about LSM stacking > configuration. > * Constify variable (spotted by Vincent Dagonneau). > > Changes since v22: > * Fix spelling (spotted by Jann Horn). > > Changes since v21: > * Update Kconfig help. > * Clean up comments. > > Changes since v18: > * Account objects to kmemcg. > > Changes since v14: > * Simplify the object, rule and ruleset management at the expense of a > less aggressive memory freeing (contributed by Jann Horn, with > additional modifications): > - Remove object->list aggregating the rules tied to an object. > - Remove landlock_get_object(), landlock_drop_object(), > {get,put}_object_cleaner() and landlock_rule_is_disabled(). > - Rewrite landlock_put_object() to use a more simple mechanism > (no tricky RCU). > - Replace enum landlock_object_type and landlock_release_object() with > landlock_object_underops->release() > - Adjust unions and Sparse annotations. > Cf. https://lore.kernel.org/lkml/CAG48ez21bEn0wL1bbmTiiu8j9jP5iEWtHOwz4tURUJ+ki0ydYw@mail.gmail.com/ > * Merge struct landlock_rule into landlock_ruleset_elem to simplify the > rule management. > * Constify variables. > * Improve kernel documentation. > * Cosmetic variable renames. > * Remove the "default" in the Kconfig (suggested by Jann Horn). > * Only use refcount_inc() through getter helpers. > * Update Kconfig description. > > Changes since v13: > * New dedicated implementation, removing the need for eBPF. > > Previous changes: > https://lore.kernel.org/lkml/20190721213116.23476-6-mic@digikod.net/ > --- > MAINTAINERS | 10 +++++ > security/Kconfig | 1 + > security/Makefile | 2 + > security/landlock/Kconfig | 21 +++++++++ > security/landlock/Makefile | 3 ++ > security/landlock/object.c | 67 ++++++++++++++++++++++++++++ > security/landlock/object.h | 91 ++++++++++++++++++++++++++++++++++++++ > 7 files changed, 195 insertions(+) > create mode 100644 security/landlock/Kconfig > create mode 100644 security/landlock/Makefile > create mode 100644 security/landlock/object.c > create mode 100644 security/landlock/object.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index d3e847f7f3dc..a0e57ade0524 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -9936,6 +9936,16 @@ F: net/core/sock_map.c > F: net/ipv4/tcp_bpf.c > F: net/ipv4/udp_bpf.c > > +LANDLOCK SECURITY MODULE > +M: Mickaël Salaün <mic@digikod.net> > +L: linux-security-module@vger.kernel.org > +S: Supported > +W: https://landlock.io > +T: git https://github.com/landlock-lsm/linux.git > +F: security/landlock/ > +K: landlock > +K: LANDLOCK > + > LANTIQ / INTEL Ethernet drivers > M: Hauke Mehrtens <hauke@hauke-m.de> > L: netdev@vger.kernel.org > diff --git a/security/Kconfig b/security/Kconfig > index 7561f6f99f1d..15a4342b5d01 100644 > --- a/security/Kconfig > +++ b/security/Kconfig > @@ -238,6 +238,7 @@ source "security/loadpin/Kconfig" > source "security/yama/Kconfig" > source "security/safesetid/Kconfig" > source "security/lockdown/Kconfig" > +source "security/landlock/Kconfig" > > source "security/integrity/Kconfig" > > diff --git a/security/Makefile b/security/Makefile > index 3baf435de541..47e432900e24 100644 > --- a/security/Makefile > +++ b/security/Makefile > @@ -13,6 +13,7 @@ subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin > subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid > subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown > subdir-$(CONFIG_BPF_LSM) += bpf > +subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock > > # always enable default capabilities > obj-y += commoncap.o > @@ -32,6 +33,7 @@ obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/ > obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ > obj-$(CONFIG_CGROUPS) += device_cgroup.o > obj-$(CONFIG_BPF_LSM) += bpf/ > +obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ > > # Object integrity file lists > subdir-$(CONFIG_INTEGRITY) += integrity > diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig > new file mode 100644 > index 000000000000..79b7d0c3b11e > --- /dev/null > +++ b/security/landlock/Kconfig > @@ -0,0 +1,21 @@ > +# SPDX-License-Identifier: GPL-2.0-only > + > +config SECURITY_LANDLOCK > + bool "Landlock support" > + depends on SECURITY > + select SECURITY_PATH > + help > + Landlock is a safe sandboxing mechanism that enables processes to "safe" probably doesn't need to be there :) > + restrict themselves (and their future children) by gradually > + enforcing tailored access control policies. A security policy is a You're redefining "security policy" which could be confusing. How about saying "a landlock security policy is a..."? > + set of access rights (e.g. open a file in read-only, make a > + directory, etc.) tied to a file hierarchy. Such policy can be > + configured and enforced by any processes for themselves thanks to s/thanks to/using the/ ? > + dedicated system calls: landlock_create_ruleset(), > + landlock_add_rule(), and landlock_restrict_self(). > + > + See Documentation/userspace-api/landlock.rst for further information. > + > + If you are unsure how to answer this question, answer N. Otherwise, > + you should also prepend "landlock," to the content of CONFIG_LSM to > + enable Landlock at boot time. > diff --git a/security/landlock/Makefile b/security/landlock/Makefile > new file mode 100644 > index 000000000000..cb6deefbf4c0 > --- /dev/null > +++ b/security/landlock/Makefile > @@ -0,0 +1,3 @@ > +obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o > + > +landlock-y := object.o > diff --git a/security/landlock/object.c b/security/landlock/object.c > new file mode 100644 > index 000000000000..d674fdf9ff04 > --- /dev/null > +++ b/security/landlock/object.c > @@ -0,0 +1,67 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Landlock LSM - Object management > + * > + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> > + * Copyright © 2018-2020 ANSSI > + */ > + > +#include <linux/bug.h> > +#include <linux/compiler_types.h> > +#include <linux/err.h> > +#include <linux/kernel.h> > +#include <linux/rcupdate.h> > +#include <linux/refcount.h> > +#include <linux/slab.h> > +#include <linux/spinlock.h> > + > +#include "object.h" > + > +struct landlock_object *landlock_create_object( > + const struct landlock_object_underops *const underops, > + void *const underobj) > +{ > + struct landlock_object *new_object; > + > + if (WARN_ON_ONCE(!underops || !underobj)) > + return ERR_PTR(-ENOENT); > + new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT); > + if (!new_object) > + return ERR_PTR(-ENOMEM); > + refcount_set(&new_object->usage, 1); > + spin_lock_init(&new_object->lock); > + new_object->underops = underops; > + new_object->underobj = underobj; > + return new_object; > +} > + > +/* > + * The caller must own the object (i.e. thanks to object->usage) to safely put > + * it. > + */ > +void landlock_put_object(struct landlock_object *const object) > +{ > + /* > + * The call to @object->underops->release(object) might sleep, e.g. > + * because of iput(). > + */ > + might_sleep(); > + if (!object) > + return; > + > + /* > + * If the @object's refcount cannot drop to zero, we can just decrement > + * the refcount without holding a lock. Otherwise, the decrement must > + * happen under @object->lock for synchronization with things like > + * get_inode_object(). > + */ > + if (refcount_dec_and_lock(&object->usage, &object->lock)) { > + __acquire(&object->lock); > + /* > + * With @object->lock initially held, remove the reference from > + * @object->underobj to @object (if it still exists). > + */ > + object->underops->release(object); > + kfree_rcu(object, rcu_free); > + } > +} > diff --git a/security/landlock/object.h b/security/landlock/object.h > new file mode 100644 > index 000000000000..56f17c51df01 > --- /dev/null > +++ b/security/landlock/object.h > @@ -0,0 +1,91 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Landlock LSM - Object management > + * > + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> > + * Copyright © 2018-2020 ANSSI > + */ > + > +#ifndef _SECURITY_LANDLOCK_OBJECT_H > +#define _SECURITY_LANDLOCK_OBJECT_H > + > +#include <linux/compiler_types.h> > +#include <linux/refcount.h> > +#include <linux/spinlock.h> > + > +struct landlock_object; > + > +/** > + * struct landlock_object_underops - Operations on an underlying object > + */ > +struct landlock_object_underops { > + /** > + * @release: Releases the underlying object (e.g. iput() for an inode). > + */ > + void (*release)(struct landlock_object *const object) > + __releases(object->lock); > +}; > + > +/** > + * struct landlock_object - Security blob tied to a kernel object > + * > + * The goal of this structure is to enable to tie a set of ephemeral access > + * rights (pertaining to different domains) to a kernel object (e.g an inode) > + * in a safe way. This implies to handle concurrent use and modification. > + * > + * The lifetime of a &struct landlock_object depends of the rules referring to > + * it. > + */ > +struct landlock_object { > + /** > + * @usage: This counter is used to tie an object to the rules matching > + * it or to keep it alive while adding a new rule. If this counter > + * reaches zero, this struct must not be modified, but this counter can > + * still be read from within an RCU read-side critical section. When > + * adding a new rule to an object with a usage counter of zero, we must > + * wait until the pointer to this object is set to NULL (or recycled). > + */ > + refcount_t usage; > + /** > + * @lock: Guards against concurrent modifications. This lock must be > + * held from the time @usage drops to zero until any weak references > + * from @underobj to this object have been cleaned up. > + * > + * Lock ordering: inode->i_lock nests inside this. > + */ > + spinlock_t lock; > + /** > + * @underobj: Used when cleaning up an object and to mark an object as > + * tied to its underlying kernel structure. This pointer is protected > + * by @lock. Cf. landlock_release_inodes() and release_inode(). > + */ > + void *underobj; > + union { > + /** > + * @rcu_free: Enables lockless use of @usage, @lock and > + * @underobj from within an RCU read-side critical section. > + * @rcu_free and @underops are only used by > + * landlock_put_object(). > + */ > + struct rcu_head rcu_free; > + /** > + * @underops: Enables landlock_put_object() to release the > + * underlying object (e.g. inode). > + */ > + const struct landlock_object_underops *underops; > + }; > +}; > + > +struct landlock_object *landlock_create_object( > + const struct landlock_object_underops *const underops, > + void *const underobj); > + > +void landlock_put_object(struct landlock_object *const object); > + > +static inline void landlock_get_object(struct landlock_object *const object) > +{ > + if (object) > + refcount_inc(&object->usage); > +} > + > +#endif /* _SECURITY_LANDLOCK_OBJECT_H */ > -- > 2.30.0
On 03/02/2021 15:21, Serge E. Hallyn wrote: > On Tue, Feb 02, 2021 at 05:26:59PM +0100, Mickaël Salaün wrote: >> From: Mickaël Salaün <mic@linux.microsoft.com> >> >> A Landlock object enables to identify a kernel object (e.g. an inode). >> A Landlock rule is a set of access rights allowed on an object. Rules >> are grouped in rulesets that may be tied to a set of processes (i.e. >> subjects) to enforce a scoped access-control (i.e. a domain). >> >> Because Landlock's goal is to empower any process (especially >> unprivileged ones) to sandbox themselves, we cannot rely on a >> system-wide object identification such as file extended attributes. >> Indeed, we need innocuous, composable and modular access-controls. >> >> The main challenge with these constraints is to identify kernel objects >> while this identification is useful (i.e. when a security policy makes >> use of this object). But this identification data should be freed once >> no policy is using it. This ephemeral tagging should not and may not be >> written in the filesystem. We then need to manage the lifetime of a >> rule according to the lifetime of its objects. To avoid a global lock, >> this implementation make use of RCU and counters to safely reference >> objects. >> >> A following commit uses this generic object management for inodes. >> >> Cc: James Morris <jmorris@namei.org> >> Cc: Kees Cook <keescook@chromium.org> >> Cc: Serge E. Hallyn <serge@hallyn.com> > > Acked-by: Serge Hallyn <serge@hallyn.com> > > Just a few suggestions for the description below. > >> Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com> >> Reviewed-by: Jann Horn <jannh@google.com> >> --- >> >> Changes since v27: >> * Update Kconfig for landlock_restrict_self(2). >> * Cosmetic fixes: use 80 columns in Kconfig and align Makefile >> declarations. >> >> Changes since v26: >> * Update Kconfig for landlock_enforce_ruleset_self(2). >> * Fix spelling. >> >> Changes since v24: >> * Fix typo in comment (spotted by Jann Horn). >> * Add Reviewed-by: Jann Horn <jannh@google.com> >> >> Changes since v23: >> * Update landlock_create_object() to return error codes instead of NULL. >> This help error handling in callers. >> * When using make oldconfig with a previous configuration already >> including the CONFIG_LSM variable, no question is asked to update its >> content. Update the Kconfig help to warn about LSM stacking >> configuration. >> * Constify variable (spotted by Vincent Dagonneau). >> >> Changes since v22: >> * Fix spelling (spotted by Jann Horn). >> >> Changes since v21: >> * Update Kconfig help. >> * Clean up comments. >> >> Changes since v18: >> * Account objects to kmemcg. >> >> Changes since v14: >> * Simplify the object, rule and ruleset management at the expense of a >> less aggressive memory freeing (contributed by Jann Horn, with >> additional modifications): >> - Remove object->list aggregating the rules tied to an object. >> - Remove landlock_get_object(), landlock_drop_object(), >> {get,put}_object_cleaner() and landlock_rule_is_disabled(). >> - Rewrite landlock_put_object() to use a more simple mechanism >> (no tricky RCU). >> - Replace enum landlock_object_type and landlock_release_object() with >> landlock_object_underops->release() >> - Adjust unions and Sparse annotations. >> Cf. https://lore.kernel.org/lkml/CAG48ez21bEn0wL1bbmTiiu8j9jP5iEWtHOwz4tURUJ+ki0ydYw@mail.gmail.com/ >> * Merge struct landlock_rule into landlock_ruleset_elem to simplify the >> rule management. >> * Constify variables. >> * Improve kernel documentation. >> * Cosmetic variable renames. >> * Remove the "default" in the Kconfig (suggested by Jann Horn). >> * Only use refcount_inc() through getter helpers. >> * Update Kconfig description. >> >> Changes since v13: >> * New dedicated implementation, removing the need for eBPF. >> >> Previous changes: >> https://lore.kernel.org/lkml/20190721213116.23476-6-mic@digikod.net/ >> --- >> MAINTAINERS | 10 +++++ >> security/Kconfig | 1 + >> security/Makefile | 2 + >> security/landlock/Kconfig | 21 +++++++++ >> security/landlock/Makefile | 3 ++ >> security/landlock/object.c | 67 ++++++++++++++++++++++++++++ >> security/landlock/object.h | 91 ++++++++++++++++++++++++++++++++++++++ >> 7 files changed, 195 insertions(+) >> create mode 100644 security/landlock/Kconfig >> create mode 100644 security/landlock/Makefile >> create mode 100644 security/landlock/object.c >> create mode 100644 security/landlock/object.h >> >> diff --git a/MAINTAINERS b/MAINTAINERS >> index d3e847f7f3dc..a0e57ade0524 100644 >> --- a/MAINTAINERS >> +++ b/MAINTAINERS >> @@ -9936,6 +9936,16 @@ F: net/core/sock_map.c >> F: net/ipv4/tcp_bpf.c >> F: net/ipv4/udp_bpf.c >> >> +LANDLOCK SECURITY MODULE >> +M: Mickaël Salaün <mic@digikod.net> >> +L: linux-security-module@vger.kernel.org >> +S: Supported >> +W: https://landlock.io >> +T: git https://github.com/landlock-lsm/linux.git >> +F: security/landlock/ >> +K: landlock >> +K: LANDLOCK >> + >> LANTIQ / INTEL Ethernet drivers >> M: Hauke Mehrtens <hauke@hauke-m.de> >> L: netdev@vger.kernel.org >> diff --git a/security/Kconfig b/security/Kconfig >> index 7561f6f99f1d..15a4342b5d01 100644 >> --- a/security/Kconfig >> +++ b/security/Kconfig >> @@ -238,6 +238,7 @@ source "security/loadpin/Kconfig" >> source "security/yama/Kconfig" >> source "security/safesetid/Kconfig" >> source "security/lockdown/Kconfig" >> +source "security/landlock/Kconfig" >> >> source "security/integrity/Kconfig" >> >> diff --git a/security/Makefile b/security/Makefile >> index 3baf435de541..47e432900e24 100644 >> --- a/security/Makefile >> +++ b/security/Makefile >> @@ -13,6 +13,7 @@ subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin >> subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid >> subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown >> subdir-$(CONFIG_BPF_LSM) += bpf >> +subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock >> >> # always enable default capabilities >> obj-y += commoncap.o >> @@ -32,6 +33,7 @@ obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/ >> obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ >> obj-$(CONFIG_CGROUPS) += device_cgroup.o >> obj-$(CONFIG_BPF_LSM) += bpf/ >> +obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ >> >> # Object integrity file lists >> subdir-$(CONFIG_INTEGRITY) += integrity >> diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig >> new file mode 100644 >> index 000000000000..79b7d0c3b11e >> --- /dev/null >> +++ b/security/landlock/Kconfig >> @@ -0,0 +1,21 @@ >> +# SPDX-License-Identifier: GPL-2.0-only >> + >> +config SECURITY_LANDLOCK >> + bool "Landlock support" >> + depends on SECURITY >> + select SECURITY_PATH >> + help >> + Landlock is a safe sandboxing mechanism that enables processes to > > "safe" probably doesn't need to be there :) > >> + restrict themselves (and their future children) by gradually >> + enforcing tailored access control policies. A security policy is a > > You're redefining "security policy" which could be confusing. How about > saying "a landlock security policy is a..."? > >> + set of access rights (e.g. open a file in read-only, make a >> + directory, etc.) tied to a file hierarchy. Such policy can be >> + configured and enforced by any processes for themselves thanks to > > s/thanks to/using the/ ? OK for these three modifications. Thanks! > >> + dedicated system calls: landlock_create_ruleset(), >> + landlock_add_rule(), and landlock_restrict_self(). >> + >> + See Documentation/userspace-api/landlock.rst for further information. >> + >> + If you are unsure how to answer this question, answer N. Otherwise, >> + you should also prepend "landlock," to the content of CONFIG_LSM to >> + enable Landlock at boot time. >> diff --git a/security/landlock/Makefile b/security/landlock/Makefile >> new file mode 100644 >> index 000000000000..cb6deefbf4c0 >> --- /dev/null >> +++ b/security/landlock/Makefile >> @@ -0,0 +1,3 @@ >> +obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o >> + >> +landlock-y := object.o >> diff --git a/security/landlock/object.c b/security/landlock/object.c >> new file mode 100644 >> index 000000000000..d674fdf9ff04 >> --- /dev/null >> +++ b/security/landlock/object.c >> @@ -0,0 +1,67 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * Landlock LSM - Object management >> + * >> + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> >> + * Copyright © 2018-2020 ANSSI >> + */ >> + >> +#include <linux/bug.h> >> +#include <linux/compiler_types.h> >> +#include <linux/err.h> >> +#include <linux/kernel.h> >> +#include <linux/rcupdate.h> >> +#include <linux/refcount.h> >> +#include <linux/slab.h> >> +#include <linux/spinlock.h> >> + >> +#include "object.h" >> + >> +struct landlock_object *landlock_create_object( >> + const struct landlock_object_underops *const underops, >> + void *const underobj) >> +{ >> + struct landlock_object *new_object; >> + >> + if (WARN_ON_ONCE(!underops || !underobj)) >> + return ERR_PTR(-ENOENT); >> + new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT); >> + if (!new_object) >> + return ERR_PTR(-ENOMEM); >> + refcount_set(&new_object->usage, 1); >> + spin_lock_init(&new_object->lock); >> + new_object->underops = underops; >> + new_object->underobj = underobj; >> + return new_object; >> +} >> + >> +/* >> + * The caller must own the object (i.e. thanks to object->usage) to safely put >> + * it. >> + */ >> +void landlock_put_object(struct landlock_object *const object) >> +{ >> + /* >> + * The call to @object->underops->release(object) might sleep, e.g. >> + * because of iput(). >> + */ >> + might_sleep(); >> + if (!object) >> + return; >> + >> + /* >> + * If the @object's refcount cannot drop to zero, we can just decrement >> + * the refcount without holding a lock. Otherwise, the decrement must >> + * happen under @object->lock for synchronization with things like >> + * get_inode_object(). >> + */ >> + if (refcount_dec_and_lock(&object->usage, &object->lock)) { >> + __acquire(&object->lock); >> + /* >> + * With @object->lock initially held, remove the reference from >> + * @object->underobj to @object (if it still exists). >> + */ >> + object->underops->release(object); >> + kfree_rcu(object, rcu_free); >> + } >> +} >> diff --git a/security/landlock/object.h b/security/landlock/object.h >> new file mode 100644 >> index 000000000000..56f17c51df01 >> --- /dev/null >> +++ b/security/landlock/object.h >> @@ -0,0 +1,91 @@ >> +/* SPDX-License-Identifier: GPL-2.0-only */ >> +/* >> + * Landlock LSM - Object management >> + * >> + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> >> + * Copyright © 2018-2020 ANSSI >> + */ >> + >> +#ifndef _SECURITY_LANDLOCK_OBJECT_H >> +#define _SECURITY_LANDLOCK_OBJECT_H >> + >> +#include <linux/compiler_types.h> >> +#include <linux/refcount.h> >> +#include <linux/spinlock.h> >> + >> +struct landlock_object; >> + >> +/** >> + * struct landlock_object_underops - Operations on an underlying object >> + */ >> +struct landlock_object_underops { >> + /** >> + * @release: Releases the underlying object (e.g. iput() for an inode). >> + */ >> + void (*release)(struct landlock_object *const object) >> + __releases(object->lock); >> +}; >> + >> +/** >> + * struct landlock_object - Security blob tied to a kernel object >> + * >> + * The goal of this structure is to enable to tie a set of ephemeral access >> + * rights (pertaining to different domains) to a kernel object (e.g an inode) >> + * in a safe way. This implies to handle concurrent use and modification. >> + * >> + * The lifetime of a &struct landlock_object depends of the rules referring to >> + * it. >> + */ >> +struct landlock_object { >> + /** >> + * @usage: This counter is used to tie an object to the rules matching >> + * it or to keep it alive while adding a new rule. If this counter >> + * reaches zero, this struct must not be modified, but this counter can >> + * still be read from within an RCU read-side critical section. When >> + * adding a new rule to an object with a usage counter of zero, we must >> + * wait until the pointer to this object is set to NULL (or recycled). >> + */ >> + refcount_t usage; >> + /** >> + * @lock: Guards against concurrent modifications. This lock must be >> + * held from the time @usage drops to zero until any weak references >> + * from @underobj to this object have been cleaned up. >> + * >> + * Lock ordering: inode->i_lock nests inside this. >> + */ >> + spinlock_t lock; >> + /** >> + * @underobj: Used when cleaning up an object and to mark an object as >> + * tied to its underlying kernel structure. This pointer is protected >> + * by @lock. Cf. landlock_release_inodes() and release_inode(). >> + */ >> + void *underobj; >> + union { >> + /** >> + * @rcu_free: Enables lockless use of @usage, @lock and >> + * @underobj from within an RCU read-side critical section. >> + * @rcu_free and @underops are only used by >> + * landlock_put_object(). >> + */ >> + struct rcu_head rcu_free; >> + /** >> + * @underops: Enables landlock_put_object() to release the >> + * underlying object (e.g. inode). >> + */ >> + const struct landlock_object_underops *underops; >> + }; >> +}; >> + >> +struct landlock_object *landlock_create_object( >> + const struct landlock_object_underops *const underops, >> + void *const underobj); >> + >> +void landlock_put_object(struct landlock_object *const object); >> + >> +static inline void landlock_get_object(struct landlock_object *const object) >> +{ >> + if (object) >> + refcount_inc(&object->usage); >> +} >> + >> +#endif /* _SECURITY_LANDLOCK_OBJECT_H */ >> -- >> 2.30.0
diff --git a/MAINTAINERS b/MAINTAINERS index d3e847f7f3dc..a0e57ade0524 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9936,6 +9936,16 @@ F: net/core/sock_map.c F: net/ipv4/tcp_bpf.c F: net/ipv4/udp_bpf.c +LANDLOCK SECURITY MODULE +M: Mickaël Salaün <mic@digikod.net> +L: linux-security-module@vger.kernel.org +S: Supported +W: https://landlock.io +T: git https://github.com/landlock-lsm/linux.git +F: security/landlock/ +K: landlock +K: LANDLOCK + LANTIQ / INTEL Ethernet drivers M: Hauke Mehrtens <hauke@hauke-m.de> L: netdev@vger.kernel.org diff --git a/security/Kconfig b/security/Kconfig index 7561f6f99f1d..15a4342b5d01 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -238,6 +238,7 @@ source "security/loadpin/Kconfig" source "security/yama/Kconfig" source "security/safesetid/Kconfig" source "security/lockdown/Kconfig" +source "security/landlock/Kconfig" source "security/integrity/Kconfig" diff --git a/security/Makefile b/security/Makefile index 3baf435de541..47e432900e24 100644 --- a/security/Makefile +++ b/security/Makefile @@ -13,6 +13,7 @@ subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown subdir-$(CONFIG_BPF_LSM) += bpf +subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock # always enable default capabilities obj-y += commoncap.o @@ -32,6 +33,7 @@ obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ obj-$(CONFIG_CGROUPS) += device_cgroup.o obj-$(CONFIG_BPF_LSM) += bpf/ +obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ # Object integrity file lists subdir-$(CONFIG_INTEGRITY) += integrity diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig new file mode 100644 index 000000000000..79b7d0c3b11e --- /dev/null +++ b/security/landlock/Kconfig @@ -0,0 +1,21 @@ +# SPDX-License-Identifier: GPL-2.0-only + +config SECURITY_LANDLOCK + bool "Landlock support" + depends on SECURITY + select SECURITY_PATH + help + Landlock is a safe sandboxing mechanism that enables processes to + restrict themselves (and their future children) by gradually + enforcing tailored access control policies. A security policy is a + set of access rights (e.g. open a file in read-only, make a + directory, etc.) tied to a file hierarchy. Such policy can be + configured and enforced by any processes for themselves thanks to + dedicated system calls: landlock_create_ruleset(), + landlock_add_rule(), and landlock_restrict_self(). + + See Documentation/userspace-api/landlock.rst for further information. + + If you are unsure how to answer this question, answer N. Otherwise, + you should also prepend "landlock," to the content of CONFIG_LSM to + enable Landlock at boot time. diff --git a/security/landlock/Makefile b/security/landlock/Makefile new file mode 100644 index 000000000000..cb6deefbf4c0 --- /dev/null +++ b/security/landlock/Makefile @@ -0,0 +1,3 @@ +obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o + +landlock-y := object.o diff --git a/security/landlock/object.c b/security/landlock/object.c new file mode 100644 index 000000000000..d674fdf9ff04 --- /dev/null +++ b/security/landlock/object.c @@ -0,0 +1,67 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Landlock LSM - Object management + * + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> + * Copyright © 2018-2020 ANSSI + */ + +#include <linux/bug.h> +#include <linux/compiler_types.h> +#include <linux/err.h> +#include <linux/kernel.h> +#include <linux/rcupdate.h> +#include <linux/refcount.h> +#include <linux/slab.h> +#include <linux/spinlock.h> + +#include "object.h" + +struct landlock_object *landlock_create_object( + const struct landlock_object_underops *const underops, + void *const underobj) +{ + struct landlock_object *new_object; + + if (WARN_ON_ONCE(!underops || !underobj)) + return ERR_PTR(-ENOENT); + new_object = kzalloc(sizeof(*new_object), GFP_KERNEL_ACCOUNT); + if (!new_object) + return ERR_PTR(-ENOMEM); + refcount_set(&new_object->usage, 1); + spin_lock_init(&new_object->lock); + new_object->underops = underops; + new_object->underobj = underobj; + return new_object; +} + +/* + * The caller must own the object (i.e. thanks to object->usage) to safely put + * it. + */ +void landlock_put_object(struct landlock_object *const object) +{ + /* + * The call to @object->underops->release(object) might sleep, e.g. + * because of iput(). + */ + might_sleep(); + if (!object) + return; + + /* + * If the @object's refcount cannot drop to zero, we can just decrement + * the refcount without holding a lock. Otherwise, the decrement must + * happen under @object->lock for synchronization with things like + * get_inode_object(). + */ + if (refcount_dec_and_lock(&object->usage, &object->lock)) { + __acquire(&object->lock); + /* + * With @object->lock initially held, remove the reference from + * @object->underobj to @object (if it still exists). + */ + object->underops->release(object); + kfree_rcu(object, rcu_free); + } +} diff --git a/security/landlock/object.h b/security/landlock/object.h new file mode 100644 index 000000000000..56f17c51df01 --- /dev/null +++ b/security/landlock/object.h @@ -0,0 +1,91 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock LSM - Object management + * + * Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net> + * Copyright © 2018-2020 ANSSI + */ + +#ifndef _SECURITY_LANDLOCK_OBJECT_H +#define _SECURITY_LANDLOCK_OBJECT_H + +#include <linux/compiler_types.h> +#include <linux/refcount.h> +#include <linux/spinlock.h> + +struct landlock_object; + +/** + * struct landlock_object_underops - Operations on an underlying object + */ +struct landlock_object_underops { + /** + * @release: Releases the underlying object (e.g. iput() for an inode). + */ + void (*release)(struct landlock_object *const object) + __releases(object->lock); +}; + +/** + * struct landlock_object - Security blob tied to a kernel object + * + * The goal of this structure is to enable to tie a set of ephemeral access + * rights (pertaining to different domains) to a kernel object (e.g an inode) + * in a safe way. This implies to handle concurrent use and modification. + * + * The lifetime of a &struct landlock_object depends of the rules referring to + * it. + */ +struct landlock_object { + /** + * @usage: This counter is used to tie an object to the rules matching + * it or to keep it alive while adding a new rule. If this counter + * reaches zero, this struct must not be modified, but this counter can + * still be read from within an RCU read-side critical section. When + * adding a new rule to an object with a usage counter of zero, we must + * wait until the pointer to this object is set to NULL (or recycled). + */ + refcount_t usage; + /** + * @lock: Guards against concurrent modifications. This lock must be + * held from the time @usage drops to zero until any weak references + * from @underobj to this object have been cleaned up. + * + * Lock ordering: inode->i_lock nests inside this. + */ + spinlock_t lock; + /** + * @underobj: Used when cleaning up an object and to mark an object as + * tied to its underlying kernel structure. This pointer is protected + * by @lock. Cf. landlock_release_inodes() and release_inode(). + */ + void *underobj; + union { + /** + * @rcu_free: Enables lockless use of @usage, @lock and + * @underobj from within an RCU read-side critical section. + * @rcu_free and @underops are only used by + * landlock_put_object(). + */ + struct rcu_head rcu_free; + /** + * @underops: Enables landlock_put_object() to release the + * underlying object (e.g. inode). + */ + const struct landlock_object_underops *underops; + }; +}; + +struct landlock_object *landlock_create_object( + const struct landlock_object_underops *const underops, + void *const underobj); + +void landlock_put_object(struct landlock_object *const object); + +static inline void landlock_get_object(struct landlock_object *const object) +{ + if (object) + refcount_inc(&object->usage); +} + +#endif /* _SECURITY_LANDLOCK_OBJECT_H */