On 19/04/2017 00:53, Kees Cook wrote: > On Tue, Mar 28, 2017 at 4:46 PM, Mickaël Salaün <mic@xxxxxxxxxxx> wrote: >> The seccomp(2) syscall can be used by a task to apply a Landlock rule to >> itself. As a seccomp filter, a Landlock rule is enforced for the current >> task and all its future children. A rule is immutable and a task can >> only add new restricting rules to itself, forming a chain of rules. >> >> A Landlock rule is tied to a Landlock event. If the use of a kernel >> object is allowed by the other Linux security mechanisms (e.g. DAC, >> capabilities, other LSM), then a Landlock event related to this kind of >> object is triggered. The chain of rules for this event is then >> evaluated. Each rule return a 32-bit value which can deny the use of a >> kernel object with a non-zero value. If every rules of the chain return >> zero, then the use of the object is allowed. >> >> Changes since v5: >> * remove struct landlock_node and use a similar inheritance mechanisme >> as seccomp-bpf (requested by Andy Lutomirski) >> * rename SECCOMP_ADD_LANDLOCK_RULE to SECCOMP_APPEND_LANDLOCK_RULE >> * rename file manager.c to providers.c >> * add comments >> * typo and cosmetic fixes >> >> Changes since v4: >> * merge manager and seccomp patches >> * return -EFAULT in seccomp(2) when user_bpf_fd is null to easely check >> if Landlock is supported >> * only allow a process with the global CAP_SYS_ADMIN to use Landlock >> (will be lifted in the future) >> * add an early check to exit as soon as possible if the current process >> does not have Landlock rules >> >> Changes since v3: >> * remove the hard link with seccomp (suggested by Andy Lutomirski and >> Kees Cook): >> * remove the cookie which could imply multiple evaluation of Landlock >> rules >> * remove the origin field in struct landlock_data >> * remove documentation fix (merged upstream) >> * rename the new seccomp command to SECCOMP_ADD_LANDLOCK_RULE >> * internal renaming >> * split commit >> * new design to be able to inherit on the fly the parent rules >> >> Changes since v2: >> * Landlock programs can now be run without seccomp filter but for any >> syscall (from the process) or interruption >> * move Landlock related functions and structs into security/landlock/* >> (to manage cgroups as well) >> * fix seccomp filter handling: run Landlock programs for each of their >> legitimate seccomp filter >> * properly clean up all seccomp results >> * cosmetic changes to ease the understanding >> * fix some ifdef >> >> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> >> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> >> Cc: James Morris <james.l.morris@xxxxxxxxxx> >> Cc: Kees Cook <keescook@xxxxxxxxxxxx> >> Cc: Serge E. Hallyn <serge@xxxxxxxxxx> >> Cc: Will Drewry <wad@xxxxxxxxxxxx> >> Link: https://lkml.kernel.org/r/c10a503d-5e35-7785-2f3d-25ed8dd63fab@xxxxxxxxxxx >> --- >> include/linux/landlock.h | 36 +++++++ >> include/linux/seccomp.h | 8 ++ >> include/uapi/linux/seccomp.h | 1 + >> kernel/fork.c | 14 ++- >> kernel/seccomp.c | 8 ++ >> security/landlock/Makefile | 2 +- >> security/landlock/hooks.c | 37 +++++++ >> security/landlock/hooks.h | 5 + >> security/landlock/init.c | 3 +- >> security/landlock/providers.c | 232 ++++++++++++++++++++++++++++++++++++++++++ >> 10 files changed, 342 insertions(+), 4 deletions(-) >> create mode 100644 security/landlock/providers.c >> >> diff --git a/include/linux/landlock.h b/include/linux/landlock.h >> index 53013dc374fe..c40ee78e86e0 100644 >> --- a/include/linux/landlock.h >> +++ b/include/linux/landlock.h >> @@ -12,6 +12,9 @@ >> #define _LINUX_LANDLOCK_H >> #ifdef CONFIG_SECURITY_LANDLOCK >> >> +#include <linux/bpf.h> /* _LANDLOCK_SUBTYPE_EVENT_LAST */ >> +#include <linux/types.h> /* atomic_t */ >> + >> /* >> * This is not intended for the UAPI headers. Each userland software should use >> * a static minimal version for the required features as explained in the >> @@ -19,5 +22,38 @@ >> */ >> #define LANDLOCK_VERSION 1 >> >> +struct landlock_rule { >> + atomic_t usage; > > This should be refcount_t. (And I should convert seccomp to use > refcount_t too!) :) OK > >> + struct landlock_rule *prev; >> + struct bpf_prog *prog; >> +}; >> + >> +/** >> + * struct landlock_events - Landlock event rules enforced on a thread >> + * >> + * This is used for low performance impact when forking a process. Instead of >> + * copying the full array and incrementing the usage of each entries, only >> + * create a pointer to &struct landlock_events and increments its usage. When >> + * appending a new rule, if &struct landlock_events is shared with other tasks, >> + * then duplicate it and append the rule to this new &struct landlock_events. >> + * >> + * @usage: reference count to manage the object lifetime. When a thread need to >> + * add Landlock rules and if @usage is greater than 1, then the thread >> + * must duplicate &struct landlock_events to not change the children's >> + * rules as well. >> + * @rules: array of non-NULL &struct landlock_rule pointers >> + */ >> +struct landlock_events { >> + atomic_t usage; >> + struct landlock_rule *rules[_LANDLOCK_SUBTYPE_EVENT_LAST]; >> +}; >> + >> +void put_landlock_events(struct landlock_events *events); >> + >> +#ifdef CONFIG_SECCOMP_FILTER > > Isn't CONFIG_SECCOMP_FILTER already required for landlock? Yes it is, but Landlock could only/also be used through cgroups in the future. :) > >> +int landlock_seccomp_append_prog(unsigned int flags, >> + const char __user *user_bpf_fd); >> +#endif /* CONFIG_SECCOMP_FILTER */ >> + >> #endif /* CONFIG_SECURITY_LANDLOCK */ >> #endif /* _LINUX_LANDLOCK_H */ >> diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h >> index e25aee2cdfc0..9a38de3c0e72 100644 >> --- a/include/linux/seccomp.h >> +++ b/include/linux/seccomp.h >> @@ -10,6 +10,10 @@ >> #include <linux/thread_info.h> >> #include <asm/seccomp.h> >> >> +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_SECURITY_LANDLOCK) >> +struct landlock_events; >> +#endif /* CONFIG_SECCOMP_FILTER && CONFIG_SECURITY_LANDLOCK */ > > Testing LANDLOCK should be sufficient, since it requires ..._FILTER. > >> + >> struct seccomp_filter; >> /** >> * struct seccomp - the state of a seccomp'ed process >> @@ -18,6 +22,7 @@ struct seccomp_filter; >> * system calls available to a process. >> * @filter: must always point to a valid seccomp-filter or NULL as it is >> * accessed without locking during system call entry. >> + * @landlock_events: contains an array of Landlock rules. >> * >> * @filter must only be accessed from the context of current as there >> * is no read locking. >> @@ -25,6 +30,9 @@ struct seccomp_filter; >> struct seccomp { >> int mode; >> struct seccomp_filter *filter; >> +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_SECURITY_LANDLOCK) >> + struct landlock_events *landlock_events; >> +#endif /* CONFIG_SECCOMP_FILTER && CONFIG_SECURITY_LANDLOCK */ > > Same. > >> }; >> >> #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER >> diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h >> index 0f238a43ff1e..74891cf60ca6 100644 >> --- a/include/uapi/linux/seccomp.h >> +++ b/include/uapi/linux/seccomp.h >> @@ -13,6 +13,7 @@ >> /* Valid operations for seccomp syscall. */ >> #define SECCOMP_SET_MODE_STRICT 0 >> #define SECCOMP_SET_MODE_FILTER 1 >> +#define SECCOMP_APPEND_LANDLOCK_RULE 2 >> >> /* Valid flags for SECCOMP_SET_MODE_FILTER */ >> #define SECCOMP_FILTER_FLAG_TSYNC 1 >> diff --git a/kernel/fork.c b/kernel/fork.c >> index a27d8e67ce33..14c09486c565 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -47,6 +47,7 @@ >> #include <linux/security.h> >> #include <linux/hugetlb.h> >> #include <linux/seccomp.h> >> +#include <linux/landlock.h> >> #include <linux/swap.h> >> #include <linux/syscalls.h> >> #include <linux/jiffies.h> >> @@ -528,7 +529,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) >> * the usage counts on the error path calling free_task. >> */ >> tsk->seccomp.filter = NULL; >> -#endif >> +#ifdef CONFIG_SECURITY_LANDLOCK >> + tsk->seccomp.landlock_events = NULL; >> +#endif /* CONFIG_SECURITY_LANDLOCK */ >> +#endif /* CONFIG_SECCOMP */ >> >> setup_thread_stack(tsk, orig); >> clear_user_return_notifier(tsk); >> @@ -1405,7 +1409,13 @@ static void copy_seccomp(struct task_struct *p) >> >> /* Ref-count the new filter user, and assign it. */ >> get_seccomp_filter(current); >> - p->seccomp = current->seccomp; >> + p->seccomp.mode = current->seccomp.mode; >> + p->seccomp.filter = current->seccomp.filter; >> +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_SECURITY_LANDLOCK) >> + p->seccomp.landlock_events = current->seccomp.landlock_events; >> + if (p->seccomp.landlock_events) >> + atomic_inc(&p->seccomp.landlock_events->usage); >> +#endif /* CONFIG_SECCOMP_FILTER && CONFIG_SECURITY_LANDLOCK */ > > Hrm. So, this needs config cleanup as above. Also, I'm going to need > some help understanding the usage tracking on landlock_events (which > should use a get/put rather than open-coding the _inc). I don't see > why individual assignments are needed here. The only thing that > matters is the usage bump. I would have expected no changes at all in > this code, actually. The filter and the events share the same usage > don't they? Right, I can move the struct landlock_event into the struct seccomp_filter. This should make the code cleaner. > >> /* >> * Explicitly enable no_new_privs here in case it got set >> diff --git a/kernel/seccomp.c b/kernel/seccomp.c >> index 326f79e32127..d122829e6da1 100644 >> --- a/kernel/seccomp.c >> +++ b/kernel/seccomp.c >> @@ -34,6 +34,7 @@ >> #include <linux/security.h> >> #include <linux/tracehook.h> >> #include <linux/uaccess.h> >> +#include <linux/landlock.h> >> >> /** >> * struct seccomp_filter - container for seccomp BPF programs >> @@ -494,6 +495,9 @@ static void put_seccomp_filter(struct seccomp_filter *filter) >> void put_seccomp(struct task_struct *tsk) >> { >> put_seccomp_filter(tsk->seccomp.filter); >> +#ifdef CONFIG_SECURITY_LANDLOCK >> + put_landlock_events(tsk->seccomp.landlock_events); >> +#endif /* CONFIG_SECURITY_LANDLOCK */ > > put_landlock_events() should be defined in a header file to be a > static inline no-op if ..._LANDLOCK isn't defined. That way we can > avoid all the #ifdef stuff here. Similarly, I think all of these > should take just task_struct so that there isn't an exposed structure > name which lets you avoid the #ifdef too. Right > >> } >> >> static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason) >> @@ -813,6 +817,10 @@ static long do_seccomp(unsigned int op, unsigned int flags, >> return seccomp_set_mode_strict(); >> case SECCOMP_SET_MODE_FILTER: >> return seccomp_set_mode_filter(flags, uargs); >> +#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_SECURITY_LANDLOCK) >> + case SECCOMP_APPEND_LANDLOCK_RULE: >> + return landlock_seccomp_append_prog(flags, uargs); >> +#endif /* CONFIG_SECCOMP_FILTER && CONFIG_SECURITY_LANDLOCK */ >> default: >> return -EINVAL; >> } >> diff --git a/security/landlock/Makefile b/security/landlock/Makefile >> index c0db504a6335..da8ba8b5183e 100644 >> --- a/security/landlock/Makefile >> +++ b/security/landlock/Makefile >> @@ -2,4 +2,4 @@ ccflags-$(CONFIG_SECURITY_LANDLOCK) += -Werror=unused-function >> >> obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o >> >> -landlock-y := init.o hooks.o hooks_fs.o >> +landlock-y := init.o providers.o hooks.o hooks_fs.o >> diff --git a/security/landlock/hooks.c b/security/landlock/hooks.c >> index eaee8162ff70..4fa7d0b38d41 100644 >> --- a/security/landlock/hooks.c >> +++ b/security/landlock/hooks.c >> @@ -95,6 +95,38 @@ bool landlock_is_valid_access(int off, int size, enum bpf_access_type type, >> return true; >> } >> >> +/** >> + * landlock_event_deny - run Landlock rules tied to an event >> + * >> + * @event_idx: event index in the rules array >> + * @ctx: non-NULL eBPF context >> + * @events: Landlock events pointer >> + * >> + * Return true if at least one rule deny the event. >> + */ >> +static bool landlock_event_deny(u32 event_idx, const struct landlock_context *ctx, >> + struct landlock_events *events) >> +{ >> + struct landlock_rule *rule; >> + >> + if (!events) >> + return false; >> + >> + for (rule = events->rules[event_idx]; rule; rule = rule->prev) { >> + u32 ret; >> + >> + if (WARN_ON(!rule->prog)) >> + continue; >> + rcu_read_lock(); >> + ret = BPF_PROG_RUN(rule->prog, (void *)ctx); >> + rcu_read_unlock(); >> + /* deny access if a program returns a value different than 0 */ >> + if (ret) >> + return true; >> + } >> + return false; >> +} >> + >> int landlock_decide(enum landlock_subtype_event event, >> __u64 ctx_values[CTX_ARG_NB], u32 cmd, const char *hook) >> { >> @@ -111,5 +143,10 @@ int landlock_decide(enum landlock_subtype_event event, >> .arg2 = ctx_values[1], >> }; >> >> +#ifdef CONFIG_SECCOMP_FILTER >> + deny = landlock_event_deny(event_idx, &ctx, >> + current->seccomp.landlock_events); >> +#endif /* CONFIG_SECCOMP_FILTER */ > > Isn't ..._FILTER required? Same as above, this is required for now but could change in the near future. :) > >> + >> return deny ? -EPERM : 0; >> } >> diff --git a/security/landlock/hooks.h b/security/landlock/hooks.h >> index 2e180f6ed86b..dd0486a4c284 100644 >> --- a/security/landlock/hooks.h >> +++ b/security/landlock/hooks.h >> @@ -12,6 +12,7 @@ >> #include <linux/bpf.h> /* enum bpf_access_type */ >> #include <linux/lsm_hooks.h> >> #include <linux/sched.h> /* struct task_struct */ >> +#include <linux/seccomp.h> >> >> /* separators */ >> #define SEP_COMMA() , >> @@ -163,7 +164,11 @@ WRAP_TYPE_RAW_C; >> >> static inline bool landlocked(const struct task_struct *task) >> { >> +#ifdef CONFIG_SECCOMP_FILTER >> + return !!(task->seccomp.landlock_events); >> +#else >> return false; >> +#endif /* CONFIG_SECCOMP_FILTER */ >> } >> >> __init void landlock_register_hooks(struct security_hook_list *hooks, int count); >> diff --git a/security/landlock/init.c b/security/landlock/init.c >> index 1c2750e12dfa..ef8a3da69860 100644 >> --- a/security/landlock/init.c >> +++ b/security/landlock/init.c >> @@ -135,7 +135,8 @@ static struct bpf_prog_type_list bpf_landlock_type __ro_after_init = { >> >> void __init landlock_add_hooks(void) >> { >> - pr_info("landlock: Version %u", LANDLOCK_VERSION); >> + pr_info("landlock: Version %u, ready to sandbox with %s\n", >> + LANDLOCK_VERSION, "seccomp"); >> landlock_add_hooks_fs(); >> security_add_hooks(NULL, 0, "landlock"); >> bpf_register_prog_type(&bpf_landlock_type); >> diff --git a/security/landlock/providers.c b/security/landlock/providers.c >> new file mode 100644 >> index 000000000000..6d867a39c947 >> --- /dev/null >> +++ b/security/landlock/providers.c >> @@ -0,0 +1,232 @@ >> +/* >> + * Landlock LSM - seccomp provider >> + * >> + * Copyright © 2017 Mickaël Salaün <mic@xxxxxxxxxxx> >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2, as >> + * published by the Free Software Foundation. >> + */ >> + >> +#include <asm/page.h> /* PAGE_SIZE */ >> +#include <linux/atomic.h> /* atomic_*(), smp_store_release() */ >> +#include <linux/bpf.h> /* bpf_prog_put() */ >> +#include <linux/filter.h> /* struct bpf_prog */ >> +#include <linux/kernel.h> /* round_up() */ >> +#include <linux/landlock.h> >> +#include <linux/sched.h> /* current_cred(), task_no_new_privs() */ >> +#include <linux/security.h> /* security_capable_noaudit() */ >> +#include <linux/slab.h> /* alloc(), kfree() */ >> +#include <linux/types.h> /* atomic_t */ >> +#include <linux/uaccess.h> /* copy_from_user() */ >> + >> +#include "common.h" >> + >> +static void put_landlock_rule(struct landlock_rule *rule) >> +{ >> + struct landlock_rule *orig = rule; >> + >> + /* clean up single-reference branches iteratively */ >> + while (orig && atomic_dec_and_test(&orig->usage)) { >> + struct landlock_rule *freeme = orig; >> + >> + bpf_prog_put(orig->prog); >> + orig = orig->prev; >> + kfree(freeme); >> + } >> +} >> + >> +void put_landlock_events(struct landlock_events *events) >> +{ >> + if (events && atomic_dec_and_test(&events->usage)) { >> + size_t i; >> + >> + for (i = 0; i < ARRAY_SIZE(events->rules); i++) >> + /* XXX: Do we need to use lockless_dereference() here? */ >> + put_landlock_rule(events->rules[i]); >> + kfree(events); >> + } >> +} >> + >> +static struct landlock_events *new_landlock_events(void) >> +{ >> + struct landlock_events *ret; >> + >> + /* array filled with NULL values */ >> + ret = kzalloc(sizeof(*ret), GFP_KERNEL); >> + if (!ret) >> + return ERR_PTR(-ENOMEM); >> + atomic_set(&ret->usage, 1); >> + return ret; >> +} >> + >> +static void add_landlock_rule(struct landlock_events *events, >> + struct landlock_rule *rule) >> +{ >> + /* subtype.landlock_rule.event > 0 for loaded programs */ >> + u32 event_idx = get_index(rule->prog->subtype.landlock_rule.event); >> + >> + rule->prev = events->rules[event_idx]; >> + WARN_ON(atomic_read(&rule->usage)); >> + atomic_set(&rule->usage, 1); >> + /* do not increment the previous rule usage */ >> + smp_store_release(&events->rules[event_idx], rule); >> +} >> + >> +/* limit Landlock events to 256KB */ >> +#define LANDLOCK_EVENTS_MAX_PAGES (1 << 6) >> + >> +/** >> + * landlock_append_prog - attach a Landlock rule to @current_events >> + * >> + * @current_events: landlock_events pointer, must be locked (if needed) to >> + * prevent a concurrent put/free. This pointer must not be >> + * freed after the call. >> + * @prog: non-NULL Landlock rule to append to @current_events. @prog will be >> + * owned by landlock_append_prog() and freed if an error happened. >> + * >> + * Return @current_events or a new pointer when OK. Return a pointer error >> + * otherwise. >> + */ >> +static struct landlock_events *landlock_append_prog( >> + struct landlock_events *current_events, struct bpf_prog *prog) >> +{ >> + struct landlock_events *new_events = current_events; >> + unsigned long pages; >> + struct landlock_rule *rule; >> + u32 event_idx; >> + >> + if (prog->type != BPF_PROG_TYPE_LANDLOCK) { >> + new_events = ERR_PTR(-EINVAL); >> + goto put_prog; >> + } >> + >> + /* validate memory size allocation */ >> + pages = prog->pages; >> + if (current_events) { >> + size_t i; >> + >> + for (i = 0; i < ARRAY_SIZE(current_events->rules); i++) { >> + struct landlock_rule *walker_r; >> + >> + for (walker_r = current_events->rules[i]; walker_r; >> + walker_r = walker_r->prev) >> + pages += walker_r->prog->pages; >> + } >> + /* count a struct landlock_events if we need to allocate one */ >> + if (atomic_read(¤t_events->usage) != 1) >> + pages += round_up(sizeof(*current_events), PAGE_SIZE) / >> + PAGE_SIZE; >> + } >> + if (pages > LANDLOCK_EVENTS_MAX_PAGES) { >> + new_events = ERR_PTR(-E2BIG); >> + goto put_prog; >> + } >> + >> + rule = kzalloc(sizeof(*rule), GFP_KERNEL); >> + if (!rule) { >> + new_events = ERR_PTR(-ENOMEM); >> + goto put_prog; >> + } >> + rule->prog = prog; >> + >> + /* subtype.landlock_rule.event > 0 for loaded programs */ >> + event_idx = get_index(rule->prog->subtype.landlock_rule.event); >> + >> + if (!new_events) { >> + /* >> + * If there is no Landlock events used by the current task, >> + * then create a new one. >> + */ >> + new_events = new_landlock_events(); >> + if (IS_ERR(new_events)) >> + goto put_rule; > > Shouldn't bpf_prog_put() get called in the face of a rule failure too? > Why separate exit paths? You're right but put_landlock_rule() call bpf_prog_put() by itself. > >> + } else if (atomic_read(¤t_events->usage) > 1) { >> + /* >> + * If the current task is not the sole user of its Landlock >> + * events, then duplicate them. >> + */ >> + size_t i; >> + >> + new_events = new_landlock_events(); >> + if (IS_ERR(new_events)) >> + goto put_rule; >> + for (i = 0; i < ARRAY_SIZE(new_events->rules); i++) { >> + new_events->rules[i] = >> + lockless_dereference(current_events->rules[i]); >> + if (new_events->rules[i]) >> + atomic_inc(&new_events->rules[i]->usage); > > I was going to ask: isn't the top-level usage counter sufficient to > track rule lifetime? But I think I see how things are tracked now: > each task_struct points to an array of rule list pointers. These > tables are duplicated when additions are made (which means each table > needs to be refcounted for the processes using it), and when a new > table is created, all the refcounters on the rules are bumped (to > track each table that references the rule), and when a new rule is > added, it's just prepended to the list for the new table to point at. That's right. > > Does this mean that rules are processed in reverse? Yes, the rules are processed from the newest to the oldest, as seccomp-bpf does with filters. > >> + } >> + >> + /* >> + * Landlock events from the current task will not be freed here >> + * because the usage is strictly greater than 1. It is only >> + * prevented to be freed by another subject thanks to the >> + * caller of landlock_append_prog() which should be locked if >> + * needed. >> + */ >> + put_landlock_events(current_events); >> + } >> + add_landlock_rule(new_events, rule); >> + return new_events; >> + >> +put_prog: >> + bpf_prog_put(prog); >> + return new_events; >> + >> +put_rule: >> + put_landlock_rule(rule); >> + return new_events; >> +} >> + >> +/** >> + * landlock_seccomp_append_prog - attach a Landlock rule to the current process >> + * >> + * current->seccomp.landlock_events is lazily allocated. When a process fork, >> + * only a pointer is copied. When a new event is added by a process, if there >> + * is other references to this process' landlock_events, then a new allocation >> + * is made to contain an array pointing to Landlock rule lists. This design >> + * enable low-performance impact and is memory efficient while keeping the >> + * property of append-only rules. >> + * >> + * @flags: not used for now, but could be used for TSYNC >> + * @user_bpf_fd: file descriptor pointing to a loaded Landlock rule >> + */ >> +#ifdef CONFIG_SECCOMP_FILTER >> +int landlock_seccomp_append_prog(unsigned int flags, >> + const char __user *user_bpf_fd) >> +{ >> + struct landlock_events *new_events; >> + struct bpf_prog *prog; >> + int bpf_fd; >> + >> + /* force no_new_privs to limit privilege escalation */ >> + if (!task_no_new_privs(current)) >> + return -EPERM; >> + /* will be removed in the future to allow unprivileged tasks */ >> + if (!capable(CAP_SYS_ADMIN)) >> + return -EPERM; >> + /* enable to check if Landlock is supported with early EFAULT */ >> + if (!user_bpf_fd) >> + return -EFAULT; >> + if (flags) >> + return -EINVAL; >> + if (copy_from_user(&bpf_fd, user_bpf_fd, sizeof(bpf_fd))) >> + return -EFAULT; > > I think this can just be get_user()? Yes, I didn't know about that. > >> + prog = bpf_prog_get(bpf_fd); >> + if (IS_ERR(prog)) >> + return PTR_ERR(prog); >> + >> + /* >> + * We don't need to lock anything for the current process hierarchy, >> + * everything is guarded by the atomic counters. >> + */ >> + new_events = landlock_append_prog(current->seccomp.landlock_events, >> + prog); >> + /* @prog is managed/freed by landlock_append_prog() */ > > Does kmemcheck notice this "leak"? (i.e. is further annotation needed?) I didn't enable kmemcheck, I will take a look at it. > >> + if (IS_ERR(new_events)) >> + return PTR_ERR(new_events); >> + current->seccomp.landlock_events = new_events; >> + return 0; >> +} >> +#endif /* CONFIG_SECCOMP_FILTER */ >> -- >> 2.11.0 >> > > >
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