#include <linux/compat.h>
#include <linux/sched.h>
#include <linux/seccomp.h>
+#include <linux/slab.h>
#include <linux/syscalls.h>
/* #define SECCOMP_DEBUG 1 */
#include <linux/filter.h>
#include <linux/ptrace.h>
#include <linux/security.h>
-#include <linux/slab.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>
#ifdef CONFIG_SECCOMP_FILTER
/**
- * seccomp_attach_filter: Attaches a seccomp filter to current.
+ * seccomp_prepare_filter: Prepares a seccomp filter for use.
* @fprog: BPF program to install
*
- * Returns 0 on success or an errno on failure.
+ * Returns filter on success or an ERR_PTR on failure.
*/
-static long seccomp_attach_filter(struct sock_fprog *fprog)
+static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
struct seccomp_filter *filter;
- unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
- unsigned long total_insns = fprog->len;
+ unsigned long fp_size;
struct sock_filter *fp;
int new_len;
long ret;
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
- return -EINVAL;
-
- for (filter = current->seccomp.filter; filter; filter = filter->prev)
- total_insns += filter->prog->len + 4; /* include a 4 instr penalty */
- if (total_insns > MAX_INSNS_PER_PATH)
- return -ENOMEM;
+ return ERR_PTR(-EINVAL);
+ BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
+ fp_size = fprog->len * sizeof(struct sock_filter);
/*
* Installing a seccomp filter requires that the task has
if (!task_no_new_privs(current) &&
security_capable_noaudit(current_cred(), current_user_ns(),
CAP_SYS_ADMIN) != 0)
- return -EACCES;
+ return ERR_PTR(-EACCES);
fp = kzalloc(fp_size, GFP_KERNEL|__GFP_NOWARN);
if (!fp)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
/* Copy the instructions from fprog. */
ret = -EFAULT;
sk_filter_select_runtime(filter->prog);
- /*
- * If there is an existing filter, make it the prev and don't drop its
- * task reference.
- */
- filter->prev = current->seccomp.filter;
- current->seccomp.filter = filter;
- return 0;
+ return filter;
free_filter_prog:
kfree(filter->prog);
kfree(filter);
free_prog:
kfree(fp);
- return ret;
+ return ERR_PTR(ret);
}
/**
- * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
+ * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
* @user_filter: pointer to the user data containing a sock_fprog.
*
* Returns 0 on success and non-zero otherwise.
*/
-static long seccomp_attach_user_filter(const char __user *user_filter)
+static struct seccomp_filter *
+seccomp_prepare_user_filter(const char __user *user_filter)
{
struct sock_fprog fprog;
- long ret = -EFAULT;
+ struct seccomp_filter *filter = ERR_PTR(-EFAULT);
#ifdef CONFIG_COMPAT
if (is_compat_task()) {
#endif
if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
goto out;
- ret = seccomp_attach_filter(&fprog);
+ filter = seccomp_prepare_filter(&fprog);
out:
- return ret;
+ return filter;
+}
+
+/**
+ * seccomp_attach_filter: validate and attach filter
+ * @flags: flags to change filter behavior
+ * @filter: seccomp filter to add to the current process
+ *
+ * Returns 0 on success, -ve on error.
+ */
+static long seccomp_attach_filter(unsigned int flags,
+ struct seccomp_filter *filter)
+{
+ unsigned long total_insns;
+ struct seccomp_filter *walker;
+
+ /* Validate resulting filter length. */
+ total_insns = filter->prog->len;
+ for (walker = current->seccomp.filter; walker; walker = walker->prev)
+ total_insns += walker->prog->len + 4; /* 4 instr penalty */
+ if (total_insns > MAX_INSNS_PER_PATH)
+ return -ENOMEM;
+
+ /*
+ * If there is an existing filter, make it the prev and don't drop its
+ * task reference.
+ */
+ filter->prev = current->seccomp.filter;
+ current->seccomp.filter = filter;
+
+ return 0;
}
/* get_seccomp_filter - increments the reference count of the filter on @tsk */
atomic_inc(&orig->usage);
}
+static inline void seccomp_filter_free(struct seccomp_filter *filter)
+{
+ if (filter) {
+ sk_filter_free(filter->prog);
+ kfree(filter);
+ }
+}
+
/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
void put_seccomp_filter(struct task_struct *tsk)
{
while (orig && atomic_dec_and_test(&orig->usage)) {
struct seccomp_filter *freeme = orig;
orig = orig->prev;
- sk_filter_free(freeme->prog);
- kfree(freeme);
+ seccomp_filter_free(freeme);
}
}
const char __user *filter)
{
const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
+ struct seccomp_filter *prepared = NULL;
long ret = -EINVAL;
/* Validate flags. */
if (flags != 0)
goto out;
+ /* Prepare the new filter before holding any locks. */
+ prepared = seccomp_prepare_user_filter(filter);
+ if (IS_ERR(prepared))
+ return PTR_ERR(prepared);
+
if (!seccomp_may_assign_mode(seccomp_mode))
goto out;
- ret = seccomp_attach_user_filter(filter);
+ ret = seccomp_attach_filter(flags, prepared);
if (ret)
goto out;
+ /* Do not free the successfully attached filter. */
+ prepared = NULL;
seccomp_assign_mode(seccomp_mode);
out:
+ seccomp_filter_free(prepared);
return ret;
}
#else
projects / linux-block.git / blobdiff