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Message-ID: <20111128191658.GA6028@albatros> Date: Mon, 28 Nov 2011 23:16:58 +0400 From: Vasiliy Kulikov <segoon@...nwall.com> To: Kees Cook <keescook@...omium.org> Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, kernel-hardening@...ts.openwall.com, "Serge E. Hallyn" <serge@...lyn.com> Subject: [RFC -resend] Make Yama pid_ns aware As Yama's sysctls are about defining a security policy for the system, it is reasonable to define it per container in case of LXC containers (or out-of-tree alternatives like OpenVZ). In my opinion they belong to pid namespace. With per-pid_ns sysctls it is possible to create multiple containers with different ptrace, /tmp, etc. policies. The patch is straightforward: 1) all sysctl variables are moved from global vars to pid_namespace fields. 2) each cloned pid ns gets the settings of the parent. 3) the variables of current pid ns are visible through sysctl interface. proc_pid_dointvec_minmax() is stolen from its ipc_ns equivalent in ipc/ipc_sysctl.c. P.S. As user namespaces are not merged yet and it's not clear when/whether they are merged, these changes belong to pid namespace for now. When user namespaces are merged, per pid_ns variables should go to struct user_namespace. It will not break ABI as userspace sees the same kernel.yama.* sysctls in both pid ns and user ns cases. Signed-off-by: Vasiliy Kulikov <segoon@...nwall.com> -- diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index 38d1032..46edaf8 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -30,6 +30,11 @@ struct pid_namespace { #ifdef CONFIG_BSD_PROCESS_ACCT struct bsd_acct_struct *bacct; #endif +#ifdef CONFIG_SECURITY_YAMA + int ptrace_scope; + int protected_sticky_symlinks; + int protected_nonaccess_hardlinks; +#endif }; extern struct pid_namespace init_pid_ns; diff --git a/kernel/pid.c b/kernel/pid.c index fa5f722..0cd8926 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -78,6 +78,11 @@ struct pid_namespace init_pid_ns = { .last_pid = 0, .level = 0, .child_reaper = &init_task, +#ifdef CONFIG_SECURITY_YAMA + .ptrace_scope = 1, + .protected_sticky_symlinks = 1, + .protected_nonaccess_hardlinks = 1, +#endif }; EXPORT_SYMBOL_GPL(init_pid_ns); diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index e9c9adc..73d47c4 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -101,6 +101,14 @@ static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_p if (err) goto out_put_parent_pid_ns; +#ifdef CONFIG_SECURITY_YAMA + ns->ptrace_scope = parent_pid_ns->ptrace_scope; + ns->protected_sticky_symlinks = + parent_pid_ns->protected_sticky_symlinks; + ns->protected_nonaccess_hardlinks = + parent_pid_ns->protected_nonaccess_hardlinks; +#endif + return ns; out_put_parent_pid_ns: diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index a92538c..cf99a8c 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -16,10 +16,7 @@ #include <linux/ptrace.h> #include <linux/prctl.h> #include <linux/ratelimit.h> - -static int ptrace_scope = 1; -static int protected_sticky_symlinks = 1; -static int protected_nonaccess_hardlinks = 1; +#include <linux/pid_namespace.h> /* describe a PTRACE relationship for potential exception */ struct ptrace_relation { @@ -250,7 +247,7 @@ static int yama_ptrace_access_check(struct task_struct *child, /* require ptrace target be a child of ptracer on attach */ if (mode == PTRACE_MODE_ATTACH && - ptrace_scope && + current->nsproxy->pid_ns->ptrace_scope && !capable(CAP_SYS_PTRACE) && !task_is_descendant(current, child) && !ptracer_exception_found(current, child)) @@ -292,7 +289,7 @@ static int yama_inode_follow_link(struct dentry *dentry, const struct inode *inode; const struct cred *cred; - if (!protected_sticky_symlinks) + if (!current->nsproxy->pid_ns->protected_sticky_symlinks) return 0; /* if inode isn't a symlink, don't try to evaluate blocking it */ @@ -362,7 +359,7 @@ static int yama_path_link(struct dentry *old_dentry, struct path *new_dir, const int mode = inode->i_mode; const struct cred *cred = current_cred(); - if (!protected_nonaccess_hardlinks) + if (!current->nsproxy->pid_ns->protected_nonaccess_hardlinks) return 0; if (cred->fsuid != inode->i_uid && @@ -395,6 +392,26 @@ static struct security_operations yama_ops = { static int zero; static int one = 1; +static void *get_pid_data(ctl_table *table) +{ + char *which = table->data; + struct pid_namespace *pid_ns = current->nsproxy->pid_ns; + which = (which - (char *)&init_pid_ns) + (char *)pid_ns; + return which; +} + +static int proc_pid_dointvec_minmax(ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + struct ctl_table pid_table; + + memcpy(&pid_table, table, sizeof(pid_table)); + pid_table.data = get_pid_data(table); + + return proc_dointvec_minmax(&pid_table, write, buffer, lenp, ppos); +} + + struct ctl_path yama_sysctl_path[] = { { .procname = "kernel", }, { .procname = "yama", }, @@ -404,28 +421,28 @@ struct ctl_path yama_sysctl_path[] = { static struct ctl_table yama_sysctl_table[] = { { .procname = "protected_sticky_symlinks", - .data = &protected_sticky_symlinks, + .data = &init_pid_ns.protected_sticky_symlinks, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_pid_dointvec_minmax, .extra1 = &zero, .extra2 = &one, }, { .procname = "protected_nonaccess_hardlinks", - .data = &protected_nonaccess_hardlinks, + .data = &init_pid_ns.protected_nonaccess_hardlinks, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_pid_dointvec_minmax, .extra1 = &zero, .extra2 = &one, }, { .procname = "ptrace_scope", - .data = &ptrace_scope, + .data = &init_pid_ns.ptrace_scope, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dointvec_minmax, + .proc_handler = proc_pid_dointvec_minmax, .extra1 = &zero, .extra2 = &one, }, ---
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