From 3d43321b7015387cfebbe26436d0e9d299162ea1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 2 Apr 2009 15:49:29 -0700 Subject: modules: sysctl to block module loading Implement a sysctl file that disables module-loading system-wide since there is no longer a viable way to remove CAP_SYS_MODULE after the system bounding capability set was removed in 2.6.25. Value can only be set to "1", and is tested only if standard capability checks allow CAP_SYS_MODULE. Given existing /dev/mem protections, this should allow administrators a one-way method to block module loading after initial boot-time module loading has finished. Signed-off-by: Kees Cook Acked-by: Serge Hallyn Signed-off-by: James Morris --- kernel/module.c | 7 +++++-- kernel/sysctl.c | 12 ++++++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/module.c b/kernel/module.c index f77ac320d0b5..eeb3f7b1383c 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -778,6 +778,9 @@ static void wait_for_zero_refcount(struct module *mod) mutex_lock(&module_mutex); } +/* Block module loading/unloading? */ +int modules_disabled = 0; + SYSCALL_DEFINE2(delete_module, const char __user *, name_user, unsigned int, flags) { @@ -785,7 +788,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, char name[MODULE_NAME_LEN]; int ret, forced = 0; - if (!capable(CAP_SYS_MODULE)) + if (!capable(CAP_SYS_MODULE) || modules_disabled) return -EPERM; if (strncpy_from_user(name, name_user, MODULE_NAME_LEN-1) < 0) @@ -2349,7 +2352,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod, int ret = 0; /* Must have permission */ - if (!capable(CAP_SYS_MODULE)) + if (!capable(CAP_SYS_MODULE) || modules_disabled) return -EPERM; /* Only one module load at a time, please */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c5ef44ff850f..2fb4246d27de 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -113,6 +113,7 @@ static int ngroups_max = NGROUPS_MAX; #ifdef CONFIG_MODULES extern char modprobe_path[]; +extern int modules_disabled; #endif #ifdef CONFIG_CHR_DEV_SG extern int sg_big_buff; @@ -533,6 +534,17 @@ static struct ctl_table kern_table[] = { .proc_handler = &proc_dostring, .strategy = &sysctl_string, }, + { + .ctl_name = CTL_UNNUMBERED, + .procname = "modules_disabled", + .data = &modules_disabled, + .maxlen = sizeof(int), + .mode = 0644, + /* only handle a transition from default "0" to "1" */ + .proc_handler = &proc_dointvec_minmax, + .extra1 = &one, + .extra2 = &one, + }, #endif #if defined(CONFIG_HOTPLUG) && defined(CONFIG_NET) { -- cgit v1.2.3 From 19e4529ee7345079eeacc8e40cf69a304a64dc23 Mon Sep 17 00:00:00 2001 From: Stephen Rothwell Date: Tue, 14 Apr 2009 17:27:18 +1000 Subject: modules: Fix up build when CONFIG_MODULE_UNLOAD=n. Commit 3d43321b7015387cfebbe26436d0e9d299162ea1 ("modules: sysctl to block module loading") introduces a modules_disabled variable that is only defined if CONFIG_MODULE_UNLOAD is enabled, despite being used in other places. This moves it up and fixes up the build. CC kernel/module.o kernel/module.c: In function 'sys_init_module': kernel/module.c:2401: error: 'modules_disabled' undeclared (first use in this function) kernel/module.c:2401: error: (Each undeclared identifier is reported only once kernel/module.c:2401: error: for each function it appears in.) make[1]: *** [kernel/module.o] Error 1 make: *** [kernel/module.o] Error 2 Signed-off-by: Paul Mundt Signed-off-by: James Morris --- kernel/module.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/module.c b/kernel/module.c index eeb3f7b1383c..ee7ab612dafa 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -71,6 +71,9 @@ static DEFINE_MUTEX(module_mutex); static LIST_HEAD(modules); +/* Block module loading/unloading? */ +int modules_disabled = 0; + /* Waiting for a module to finish initializing? */ static DECLARE_WAIT_QUEUE_HEAD(module_wq); @@ -778,9 +781,6 @@ static void wait_for_zero_refcount(struct module *mod) mutex_lock(&module_mutex); } -/* Block module loading/unloading? */ -int modules_disabled = 0; - SYSCALL_DEFINE2(delete_module, const char __user *, name_user, unsigned int, flags) { -- cgit v1.2.3 From 3bcac0263f0b45e67a64034ebcb69eb9abb742f4 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 29 Apr 2009 13:45:05 +0100 Subject: SELinux: Don't flush inherited SIGKILL during execve() Don't flush inherited SIGKILL during execve() in SELinux's post cred commit hook. This isn't really a security problem: if the SIGKILL came before the credentials were changed, then we were right to receive it at the time, and should honour it; if it came after the creds were changed, then we definitely should honour it; and in any case, all that will happen is that the process will be scrapped before it ever returns to userspace. Signed-off-by: David Howells Signed-off-by: Oleg Nesterov Signed-off-by: James Morris --- kernel/signal.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/signal.c b/kernel/signal.c index 1c8814481a11..f93efec14ff5 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -238,14 +238,19 @@ void flush_sigqueue(struct sigpending *queue) /* * Flush all pending signals for a task. */ +void __flush_signals(struct task_struct *t) +{ + clear_tsk_thread_flag(t, TIF_SIGPENDING); + flush_sigqueue(&t->pending); + flush_sigqueue(&t->signal->shared_pending); +} + void flush_signals(struct task_struct *t) { unsigned long flags; spin_lock_irqsave(&t->sighand->siglock, flags); - clear_tsk_thread_flag(t, TIF_SIGPENDING); - flush_sigqueue(&t->pending); - flush_sigqueue(&t->signal->shared_pending); + __flush_signals(t); spin_unlock_irqrestore(&t->sighand->siglock, flags); } -- cgit v1.2.3 From 78a3d9d5654a7fd99cf8b2ab06b9497b9c7aad64 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 29 Apr 2009 18:01:23 +0200 Subject: do_wait: do take security_task_wait() into account I was never able to understand what should we actually do when security_task_wait() fails, but the current code doesn't look right. If ->task_wait() returns the error, we update *notask_error correctly. But then we either reap the child (despite the fact this was forbidden) or clear *notask_error (and hide the securiy policy problems). This patch assumes that "stolen by ptrace" doesn't matter. If selinux denies the child we should ignore it but make sure we report -EACCESS instead of -ECHLD if there are no other eligible children. Signed-off-by: Oleg Nesterov Acked-by: Roland McGrath Signed-off-by: James Morris --- kernel/exit.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel') diff --git a/kernel/exit.c b/kernel/exit.c index 167e1e3ad7c6..d2e8239ea187 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1582,6 +1582,7 @@ static int wait_consider_task(struct task_struct *parent, int ptrace, */ if (*notask_error) *notask_error = ret; + return 0; } if (likely(!ptrace) && unlikely(p->ptrace)) { -- cgit v1.2.3 From 5e751e992f3fb08ba35e1ca8095ec8fbf9eda523 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 8 May 2009 13:55:22 +0100 Subject: CRED: Rename cred_exec_mutex to reflect that it's a guard against ptrace Rename cred_exec_mutex to reflect that it's a guard against foreign intervention on a process's credential state, such as is made by ptrace(). The attachment of a debugger to a process affects execve()'s calculation of the new credential state - _and_ also setprocattr()'s calculation of that state. Signed-off-by: David Howells Signed-off-by: James Morris --- kernel/cred.c | 4 ++-- kernel/ptrace.c | 9 +++++---- 2 files changed, 7 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/cred.c b/kernel/cred.c index 3a039189d707..1bb4d7e5d616 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -167,7 +167,7 @@ EXPORT_SYMBOL(prepare_creds); /* * Prepare credentials for current to perform an execve() - * - The caller must hold current->cred_exec_mutex + * - The caller must hold current->cred_guard_mutex */ struct cred *prepare_exec_creds(void) { @@ -276,7 +276,7 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) struct cred *new; int ret; - mutex_init(&p->cred_exec_mutex); + mutex_init(&p->cred_guard_mutex); if ( #ifdef CONFIG_KEYS diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 0692ab5a0d67..27ac80298bfa 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -185,10 +185,11 @@ int ptrace_attach(struct task_struct *task) if (same_thread_group(task, current)) goto out; - /* Protect exec's credential calculations against our interference; - * SUID, SGID and LSM creds get determined differently under ptrace. + /* Protect the target's credential calculations against our + * interference; SUID, SGID and LSM creds get determined differently + * under ptrace. */ - retval = mutex_lock_interruptible(&task->cred_exec_mutex); + retval = mutex_lock_interruptible(&task->cred_guard_mutex); if (retval < 0) goto out; @@ -232,7 +233,7 @@ repeat: bad: write_unlock_irqrestore(&tasklist_lock, flags); task_unlock(task); - mutex_unlock(&task->cred_exec_mutex); + mutex_unlock(&task->cred_guard_mutex); out: return retval; } -- cgit v1.2.3 From e0a94c2a63f2644826069044649669b5e7ca75d3 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 3 Jun 2009 16:04:31 -0400 Subject: security: use mmap_min_addr indepedently of security models This patch removes the dependency of mmap_min_addr on CONFIG_SECURITY. It also sets a default mmap_min_addr of 4096. mmapping of addresses below 4096 will only be possible for processes with CAP_SYS_RAWIO. Signed-off-by: Christoph Lameter Acked-by: Eric Paris Looks-ok-by: Linus Torvalds Signed-off-by: James Morris --- kernel/sysctl.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'kernel') diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 149581fb48ab..45bd711a242e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1237,7 +1237,6 @@ static struct ctl_table vm_table[] = { .strategy = &sysctl_jiffies, }, #endif -#ifdef CONFIG_SECURITY { .ctl_name = CTL_UNNUMBERED, .procname = "mmap_min_addr", @@ -1246,7 +1245,6 @@ static struct ctl_table vm_table[] = { .mode = 0644, .proc_handler = &proc_doulongvec_minmax, }, -#endif #ifdef CONFIG_NUMA { .ctl_name = CTL_UNNUMBERED, -- cgit v1.2.3