Re: [RFC v1 14/14] krsi: Pin arg pages only when needed
On 9/15/19 2:40 AM, KP Singh wrote:
> On 15-Sep 00:33, Yonghong Song wrote:
>>
>>
>> On 9/10/19 12:55 PM, KP Singh wrote:
>>> From: KP Singh
>>>
>>> Adds a callback which is called when a new program is attached
>>> to a hook. The callback registered by the process_exection hook
>>> checks if a program that has calls to a helper that requires pages to
>>> be pinned (eg. krsi_get_env_var).
>>>
>>> Signed-off-by: KP Singh
>>> ---
>>>include/linux/krsi.h | 1 +
>>>security/krsi/include/hooks.h | 5 ++-
>>>security/krsi/include/krsi_init.h | 7
>>>security/krsi/krsi.c | 62 ---
>>>security/krsi/ops.c | 10 -
>>>5 files changed, 77 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/include/linux/krsi.h b/include/linux/krsi.h
>>> index c7d1790d0c1f..e443d0309764 100644
>>> --- a/include/linux/krsi.h
>>> +++ b/include/linux/krsi.h
>>> @@ -7,6 +7,7 @@
>>>
>>>#ifdef CONFIG_SECURITY_KRSI
>>>int krsi_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog);
>>> +extern const struct bpf_func_proto krsi_get_env_var_proto;
>>>#else
>>>static inline int krsi_prog_attach(const union bpf_attr *attr,
>>>struct bpf_prog *prog)
>>> diff --git a/security/krsi/include/hooks.h b/security/krsi/include/hooks.h
>>> index e070c452b5de..38293125ff99 100644
>>> --- a/security/krsi/include/hooks.h
>>> +++ b/security/krsi/include/hooks.h
>>> @@ -8,7 +8,7 @@
>>> *
>>> * Format:
>>> *
>>> - * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN)
>>> + * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN, CALLBACK)
>>> *
>>> * KRSI adds one layer of indirection between the name of the hook and
>>> the name
>>> * it exposes to the userspace in Security FS to prevent the userspace
>>> from
>>> @@ -18,4 +18,5 @@
>>>KRSI_HOOK_INIT(PROCESS_EXECUTION,
>>>process_execution,
>>>bprm_check_security,
>>> - krsi_process_execution)
>>> + krsi_process_execution,
>>> + krsi_process_execution_cb)
>>> diff --git a/security/krsi/include/krsi_init.h
>>> b/security/krsi/include/krsi_init.h
>>> index 6152847c3b08..99801d5b273a 100644
>>> --- a/security/krsi/include/krsi_init.h
>>> +++ b/security/krsi/include/krsi_init.h
>>> @@ -31,6 +31,8 @@ struct krsi_ctx {
>>> };
>>>};
>>>
>>> +typedef int (*krsi_prog_attach_t) (struct bpf_prog_array *);
>>> +
>>>/*
>>> * The LSM creates one file per hook.
>>> *
>>> @@ -61,6 +63,11 @@ struct krsi_hook {
>>> * The eBPF programs that are attached to this hook.
>>> */
>>> struct bpf_prog_array __rcu *progs;
>>> + /*
>>> +* The attach callback is called before a new program is attached
>>> +* to the hook and is passed the updated bpf_prog_array as an argument.
>>> +*/
>>> + krsi_prog_attach_t attach_callback;
>>>};
>>>
>>>extern struct krsi_hook krsi_hooks_list[];
>>> diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c
>>> index 00a7150c1b22..a4443d7aa150 100644
>>> --- a/security/krsi/krsi.c
>>> +++ b/security/krsi/krsi.c
>>> @@ -5,15 +5,65 @@
>>>#include
>>>#include
>>>#include
>>> +#include
>>>#include
>>>
>>>#include "krsi_init.h"
>>>
>>> +/*
>>> + * need_arg_pages is only updated in bprm_check_security_cb
>>> + * when a mutex on krsi_hook for bprm_check_security is already
>>> + * held. need_arg_pages avoids pinning pages when no program
>>> + * that needs them is attached to the hook.
>>> + */
>>> +static bool need_arg_pages;
>>> +
>>> +/*
>>> + * Checks if the instruction is a BPF_CALL to an eBPF helper located
>>> + * at the given address.
>>> + */
>>> +static inline bool bpf_is_call_to_func(struct bpf_insn *insn,
>>> + void *func_addr)
>>> +{
>>> + u8 opcode = BPF_OP(insn->code);
>>> +
>>> + if (opcode != BPF_CALL)
>>> + return false;
>>> +
>>> + if (insn->src_reg == BPF_PSEUDO_CALL)
>>> + return false;
>>> +
>>> + /*
>>> +* The BPF verifier updates the value of insn->imm from the
>>> +* enum bpf_func_id to the offset of the address of helper
>>> +* from the __bpf_call_base.
>>> +*/
>>> + return __bpf_call_base + insn->imm == func_addr;
>>
>> In how many cases, krsi program does not have krsi_get_env_var() helper?
>
> It depends, if the user does not choose to use log environment
> variables or use the the value as a part of their MAC policy, the
> pinning of the pages is not needed.
Thanks. I just want to know whether we want to optimize such cases.
I am not a security expert, so I am okay with whatever decision you
made.
>
> Also, the pinning is needed since eBPF helpers cannot run a non-atomic
> context. It would not be needed if "sleepable eBPF" becomes a thing.
Indeed. 'sleepable BPF' might be also a good thing for realtime linux.
Some works need to address bpf area spin lock, per
Re: [RFC v1 14/14] krsi: Pin arg pages only when needed
On 15-Sep 00:33, Yonghong Song wrote:
>
>
> On 9/10/19 12:55 PM, KP Singh wrote:
> > From: KP Singh
> >
> > Adds a callback which is called when a new program is attached
> > to a hook. The callback registered by the process_exection hook
> > checks if a program that has calls to a helper that requires pages to
> > be pinned (eg. krsi_get_env_var).
> >
> > Signed-off-by: KP Singh
> > ---
> > include/linux/krsi.h | 1 +
> > security/krsi/include/hooks.h | 5 ++-
> > security/krsi/include/krsi_init.h | 7
> > security/krsi/krsi.c | 62 ---
> > security/krsi/ops.c | 10 -
> > 5 files changed, 77 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux/krsi.h b/include/linux/krsi.h
> > index c7d1790d0c1f..e443d0309764 100644
> > --- a/include/linux/krsi.h
> > +++ b/include/linux/krsi.h
> > @@ -7,6 +7,7 @@
> >
> > #ifdef CONFIG_SECURITY_KRSI
> > int krsi_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog);
> > +extern const struct bpf_func_proto krsi_get_env_var_proto;
> > #else
> > static inline int krsi_prog_attach(const union bpf_attr *attr,
> >struct bpf_prog *prog)
> > diff --git a/security/krsi/include/hooks.h b/security/krsi/include/hooks.h
> > index e070c452b5de..38293125ff99 100644
> > --- a/security/krsi/include/hooks.h
> > +++ b/security/krsi/include/hooks.h
> > @@ -8,7 +8,7 @@
> >*
> >* Format:
> >*
> > - * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN)
> > + * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN, CALLBACK)
> >*
> >* KRSI adds one layer of indirection between the name of the hook and
> > the name
> >* it exposes to the userspace in Security FS to prevent the userspace
> > from
> > @@ -18,4 +18,5 @@
> > KRSI_HOOK_INIT(PROCESS_EXECUTION,
> >process_execution,
> >bprm_check_security,
> > - krsi_process_execution)
> > + krsi_process_execution,
> > + krsi_process_execution_cb)
> > diff --git a/security/krsi/include/krsi_init.h
> > b/security/krsi/include/krsi_init.h
> > index 6152847c3b08..99801d5b273a 100644
> > --- a/security/krsi/include/krsi_init.h
> > +++ b/security/krsi/include/krsi_init.h
> > @@ -31,6 +31,8 @@ struct krsi_ctx {
> > };
> > };
> >
> > +typedef int (*krsi_prog_attach_t) (struct bpf_prog_array *);
> > +
> > /*
> >* The LSM creates one file per hook.
> >*
> > @@ -61,6 +63,11 @@ struct krsi_hook {
> > * The eBPF programs that are attached to this hook.
> > */
> > struct bpf_prog_array __rcu *progs;
> > + /*
> > +* The attach callback is called before a new program is attached
> > +* to the hook and is passed the updated bpf_prog_array as an argument.
> > +*/
> > + krsi_prog_attach_t attach_callback;
> > };
> >
> > extern struct krsi_hook krsi_hooks_list[];
> > diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c
> > index 00a7150c1b22..a4443d7aa150 100644
> > --- a/security/krsi/krsi.c
> > +++ b/security/krsi/krsi.c
> > @@ -5,15 +5,65 @@
> > #include
> > #include
> > #include
> > +#include
> > #include
> >
> > #include "krsi_init.h"
> >
> > +/*
> > + * need_arg_pages is only updated in bprm_check_security_cb
> > + * when a mutex on krsi_hook for bprm_check_security is already
> > + * held. need_arg_pages avoids pinning pages when no program
> > + * that needs them is attached to the hook.
> > + */
> > +static bool need_arg_pages;
> > +
> > +/*
> > + * Checks if the instruction is a BPF_CALL to an eBPF helper located
> > + * at the given address.
> > + */
> > +static inline bool bpf_is_call_to_func(struct bpf_insn *insn,
> > + void *func_addr)
> > +{
> > + u8 opcode = BPF_OP(insn->code);
> > +
> > + if (opcode != BPF_CALL)
> > + return false;
> > +
> > + if (insn->src_reg == BPF_PSEUDO_CALL)
> > + return false;
> > +
> > + /*
> > +* The BPF verifier updates the value of insn->imm from the
> > +* enum bpf_func_id to the offset of the address of helper
> > +* from the __bpf_call_base.
> > +*/
> > + return __bpf_call_base + insn->imm == func_addr;
>
> In how many cases, krsi program does not have krsi_get_env_var() helper?
It depends, if the user does not choose to use log environment
variables or use the the value as a part of their MAC policy, the
pinning of the pages is not needed.
Also, the pinning is needed since eBPF helpers cannot run a non-atomic
context. It would not be needed if "sleepable eBPF" becomes a thing.
- KP
>
> > +}
> > +
> > +static int krsi_process_execution_cb(struct bpf_prog_array *array)
> > +{
> > + struct bpf_prog_array_item *item = array->items;
> > + struct bpf_prog *p;
> > + const struct bpf_func_proto *proto = _get_env_var_proto;
> > + int i;
> > +
> > + while ((p = READ_ONCE(item->prog))) {
> > + for (i = 0; i <
Re: [RFC v1 14/14] krsi: Pin arg pages only when needed
On 9/10/19 12:55 PM, KP Singh wrote:
> From: KP Singh
>
> Adds a callback which is called when a new program is attached
> to a hook. The callback registered by the process_exection hook
> checks if a program that has calls to a helper that requires pages to
> be pinned (eg. krsi_get_env_var).
>
> Signed-off-by: KP Singh
> ---
> include/linux/krsi.h | 1 +
> security/krsi/include/hooks.h | 5 ++-
> security/krsi/include/krsi_init.h | 7
> security/krsi/krsi.c | 62 ---
> security/krsi/ops.c | 10 -
> 5 files changed, 77 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/krsi.h b/include/linux/krsi.h
> index c7d1790d0c1f..e443d0309764 100644
> --- a/include/linux/krsi.h
> +++ b/include/linux/krsi.h
> @@ -7,6 +7,7 @@
>
> #ifdef CONFIG_SECURITY_KRSI
> int krsi_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog);
> +extern const struct bpf_func_proto krsi_get_env_var_proto;
> #else
> static inline int krsi_prog_attach(const union bpf_attr *attr,
> struct bpf_prog *prog)
> diff --git a/security/krsi/include/hooks.h b/security/krsi/include/hooks.h
> index e070c452b5de..38293125ff99 100644
> --- a/security/krsi/include/hooks.h
> +++ b/security/krsi/include/hooks.h
> @@ -8,7 +8,7 @@
>*
>* Format:
>*
> - * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN)
> + * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN, CALLBACK)
>*
>* KRSI adds one layer of indirection between the name of the hook and the
> name
>* it exposes to the userspace in Security FS to prevent the userspace from
> @@ -18,4 +18,5 @@
> KRSI_HOOK_INIT(PROCESS_EXECUTION,
> process_execution,
> bprm_check_security,
> -krsi_process_execution)
> +krsi_process_execution,
> +krsi_process_execution_cb)
> diff --git a/security/krsi/include/krsi_init.h
> b/security/krsi/include/krsi_init.h
> index 6152847c3b08..99801d5b273a 100644
> --- a/security/krsi/include/krsi_init.h
> +++ b/security/krsi/include/krsi_init.h
> @@ -31,6 +31,8 @@ struct krsi_ctx {
> };
> };
>
> +typedef int (*krsi_prog_attach_t) (struct bpf_prog_array *);
> +
> /*
>* The LSM creates one file per hook.
>*
> @@ -61,6 +63,11 @@ struct krsi_hook {
>* The eBPF programs that are attached to this hook.
>*/
> struct bpf_prog_array __rcu *progs;
> + /*
> + * The attach callback is called before a new program is attached
> + * to the hook and is passed the updated bpf_prog_array as an argument.
> + */
> + krsi_prog_attach_t attach_callback;
> };
>
> extern struct krsi_hook krsi_hooks_list[];
> diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c
> index 00a7150c1b22..a4443d7aa150 100644
> --- a/security/krsi/krsi.c
> +++ b/security/krsi/krsi.c
> @@ -5,15 +5,65 @@
> #include
> #include
> #include
> +#include
> #include
>
> #include "krsi_init.h"
>
> +/*
> + * need_arg_pages is only updated in bprm_check_security_cb
> + * when a mutex on krsi_hook for bprm_check_security is already
> + * held. need_arg_pages avoids pinning pages when no program
> + * that needs them is attached to the hook.
> + */
> +static bool need_arg_pages;
> +
> +/*
> + * Checks if the instruction is a BPF_CALL to an eBPF helper located
> + * at the given address.
> + */
> +static inline bool bpf_is_call_to_func(struct bpf_insn *insn,
> +void *func_addr)
> +{
> + u8 opcode = BPF_OP(insn->code);
> +
> + if (opcode != BPF_CALL)
> + return false;
> +
> + if (insn->src_reg == BPF_PSEUDO_CALL)
> + return false;
> +
> + /*
> + * The BPF verifier updates the value of insn->imm from the
> + * enum bpf_func_id to the offset of the address of helper
> + * from the __bpf_call_base.
> + */
> + return __bpf_call_base + insn->imm == func_addr;
In how many cases, krsi program does not have krsi_get_env_var() helper?
> +}
> +
> +static int krsi_process_execution_cb(struct bpf_prog_array *array)
> +{
> + struct bpf_prog_array_item *item = array->items;
> + struct bpf_prog *p;
> + const struct bpf_func_proto *proto = _get_env_var_proto;
> + int i;
> +
> + while ((p = READ_ONCE(item->prog))) {
> + for (i = 0; i < p->len; i++) {
> + if (bpf_is_call_to_func(>insnsi[i], proto->func))
> + need_arg_pages = true;
> + }
> + item++;
> + }
> + return 0;
> +}
> +
> struct krsi_hook krsi_hooks_list[] = {
> - #define KRSI_HOOK_INIT(TYPE, NAME, H, I) \
> + #define KRSI_HOOK_INIT(TYPE, NAME, H, I, CB) \
> [TYPE] = { \
> .h_type = TYPE, \
> .name = #NAME, \
> + .attach_callback = CB, \
> },
>
[RFC v1 14/14] krsi: Pin arg pages only when needed
From: KP Singh
Adds a callback which is called when a new program is attached
to a hook. The callback registered by the process_exection hook
checks if a program that has calls to a helper that requires pages to
be pinned (eg. krsi_get_env_var).
Signed-off-by: KP Singh
---
include/linux/krsi.h | 1 +
security/krsi/include/hooks.h | 5 ++-
security/krsi/include/krsi_init.h | 7
security/krsi/krsi.c | 62 ---
security/krsi/ops.c | 10 -
5 files changed, 77 insertions(+), 8 deletions(-)
diff --git a/include/linux/krsi.h b/include/linux/krsi.h
index c7d1790d0c1f..e443d0309764 100644
--- a/include/linux/krsi.h
+++ b/include/linux/krsi.h
@@ -7,6 +7,7 @@
#ifdef CONFIG_SECURITY_KRSI
int krsi_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog);
+extern const struct bpf_func_proto krsi_get_env_var_proto;
#else
static inline int krsi_prog_attach(const union bpf_attr *attr,
struct bpf_prog *prog)
diff --git a/security/krsi/include/hooks.h b/security/krsi/include/hooks.h
index e070c452b5de..38293125ff99 100644
--- a/security/krsi/include/hooks.h
+++ b/security/krsi/include/hooks.h
@@ -8,7 +8,7 @@
*
* Format:
*
- * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN)
+ * KRSI_HOOK_INIT(TYPE, NAME, LSM_HOOK, KRSI_HOOK_FN, CALLBACK)
*
* KRSI adds one layer of indirection between the name of the hook and the name
* it exposes to the userspace in Security FS to prevent the userspace from
@@ -18,4 +18,5 @@
KRSI_HOOK_INIT(PROCESS_EXECUTION,
process_execution,
bprm_check_security,
- krsi_process_execution)
+ krsi_process_execution,
+ krsi_process_execution_cb)
diff --git a/security/krsi/include/krsi_init.h
b/security/krsi/include/krsi_init.h
index 6152847c3b08..99801d5b273a 100644
--- a/security/krsi/include/krsi_init.h
+++ b/security/krsi/include/krsi_init.h
@@ -31,6 +31,8 @@ struct krsi_ctx {
};
};
+typedef int (*krsi_prog_attach_t) (struct bpf_prog_array *);
+
/*
* The LSM creates one file per hook.
*
@@ -61,6 +63,11 @@ struct krsi_hook {
* The eBPF programs that are attached to this hook.
*/
struct bpf_prog_array __rcu *progs;
+ /*
+* The attach callback is called before a new program is attached
+* to the hook and is passed the updated bpf_prog_array as an argument.
+*/
+ krsi_prog_attach_t attach_callback;
};
extern struct krsi_hook krsi_hooks_list[];
diff --git a/security/krsi/krsi.c b/security/krsi/krsi.c
index 00a7150c1b22..a4443d7aa150 100644
--- a/security/krsi/krsi.c
+++ b/security/krsi/krsi.c
@@ -5,15 +5,65 @@
#include
#include
#include
+#include
#include
#include "krsi_init.h"
+/*
+ * need_arg_pages is only updated in bprm_check_security_cb
+ * when a mutex on krsi_hook for bprm_check_security is already
+ * held. need_arg_pages avoids pinning pages when no program
+ * that needs them is attached to the hook.
+ */
+static bool need_arg_pages;
+
+/*
+ * Checks if the instruction is a BPF_CALL to an eBPF helper located
+ * at the given address.
+ */
+static inline bool bpf_is_call_to_func(struct bpf_insn *insn,
+ void *func_addr)
+{
+ u8 opcode = BPF_OP(insn->code);
+
+ if (opcode != BPF_CALL)
+ return false;
+
+ if (insn->src_reg == BPF_PSEUDO_CALL)
+ return false;
+
+ /*
+* The BPF verifier updates the value of insn->imm from the
+* enum bpf_func_id to the offset of the address of helper
+* from the __bpf_call_base.
+*/
+ return __bpf_call_base + insn->imm == func_addr;
+}
+
+static int krsi_process_execution_cb(struct bpf_prog_array *array)
+{
+ struct bpf_prog_array_item *item = array->items;
+ struct bpf_prog *p;
+ const struct bpf_func_proto *proto = _get_env_var_proto;
+ int i;
+
+ while ((p = READ_ONCE(item->prog))) {
+ for (i = 0; i < p->len; i++) {
+ if (bpf_is_call_to_func(>insnsi[i], proto->func))
+ need_arg_pages = true;
+ }
+ item++;
+ }
+ return 0;
+}
+
struct krsi_hook krsi_hooks_list[] = {
- #define KRSI_HOOK_INIT(TYPE, NAME, H, I) \
+ #define KRSI_HOOK_INIT(TYPE, NAME, H, I, CB) \
[TYPE] = { \
.h_type = TYPE, \
.name = #NAME, \
+ .attach_callback = CB, \
},
#include "hooks.h"
#undef KRSI_HOOK_INIT
@@ -75,9 +125,11 @@ static int krsi_process_execution(struct linux_binprm *bprm)
.bprm = bprm,
};
- ret = pin_arg_pages(_ctx);
- if (ret < 0)
- goto out_arg_pages;
+ if (READ_ONCE(need_arg_pages)) {
+ ret =
