When a process is made non-dumpable, the action implies a higher level of security implicitly as its memory is imposed with access restriction.
A call to update_process_security() is added to update security defenses according to a process's dumpability and its implied security level. Architecture specific defenses is erected for threads in the process by calling arch_set_security(task, SECURITY_LEVEL_HIGH) or the defenses relaxed via arch_set_security(task, SECURITY_LEVEL_NORMAL). Such defenses may incur extra overhead and is reserved for tasks needing high security. Signed-off-by: Tim Chen <[email protected]> --- fs/exec.c | 2 ++ include/linux/security.h | 6 ++++++ kernel/cred.c | 5 ++++- kernel/sys.c | 1 + security/security.c | 31 +++++++++++++++++++++++++++++++ 5 files changed, 44 insertions(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index 1ebf6e5..e70c8a7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1366,6 +1366,8 @@ void setup_new_exec(struct linux_binprm * bprm) else set_dumpable(current->mm, SUID_DUMP_USER); + update_process_security(current); + arch_setup_new_exec(); perf_event_exec(); __set_task_comm(current, kbasename(bprm->filename), true); diff --git a/include/linux/security.h b/include/linux/security.h index 75f4156..469d05f 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -61,6 +61,12 @@ struct mm_struct; /* LSM Agnostic defines for sb_set_mnt_opts */ #define SECURITY_LSM_NATIVE_LABELS 1 +/* Security level */ +#define SECURITY_NORMAL 0 +#define SECURITY_HIGH 1 + +extern int update_process_security(struct task_struct *task); + struct ctl_table; struct audit_krule; struct user_namespace; diff --git a/kernel/cred.c b/kernel/cred.c index ecf0365..0806a74 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -19,6 +19,7 @@ #include <linux/security.h> #include <linux/binfmts.h> #include <linux/cn_proc.h> +#include <linux/security.h> #if 0 #define kdebug(FMT, ...) \ @@ -445,8 +446,10 @@ int commit_creds(struct cred *new) !uid_eq(old->fsuid, new->fsuid) || !gid_eq(old->fsgid, new->fsgid) || !cred_cap_issubset(old, new)) { - if (task->mm) + if (task->mm) { set_dumpable(task->mm, suid_dumpable); + update_process_security(task); + } task->pdeath_signal = 0; smp_wmb(); } diff --git a/kernel/sys.c b/kernel/sys.c index cf5c675..c6f179a 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2293,6 +2293,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, break; } set_dumpable(me->mm, arg2); + update_process_security(me); break; case PR_SET_UNALIGN: diff --git a/security/security.c b/security/security.c index 736e78d..12460f2 100644 --- a/security/security.c +++ b/security/security.c @@ -28,6 +28,8 @@ #include <linux/personality.h> #include <linux/backing-dev.h> #include <linux/string.h> +#include <linux/coredump.h> +#include <linux/sched/signal.h> #include <net/flow.h> #include <trace/events/initcall.h> @@ -1353,6 +1355,35 @@ int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) } EXPORT_SYMBOL(security_inode_getsecctx); +void __weak arch_set_security(struct task_struct *task, + unsigned int security_level) +{ +} + +int update_process_security(struct task_struct *task) +{ + unsigned long flags; + struct task_struct *t; + int security_level; + + if (!task->mm) + return -EINVAL; + + if (!lock_task_sighand(task, &flags)) + return -ESRCH; + + if (get_dumpable(task->mm) != SUID_DUMP_USER) + security_level = SECURITY_HIGH; + else + security_level = SECURITY_NORMAL; + + for_each_thread(task, t) + arch_set_security(task, security_level); + + unlock_task_sighand(task, &flags); + return 0; +} + #ifdef CONFIG_SECURITY_NETWORK int security_unix_stream_connect(struct sock *sock, struct sock *other, struct sock *newsk) -- 2.9.4
