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authorLinus Torvalds <torvalds@linux-foundation.org>2019-11-30 17:23:16 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-30 17:23:16 -0800
commitb94ae8ad9fe79da61231999f347f79645b909bda (patch)
tree094ebce460d7903a1ab94616dd1f021ab9795955 /include
parent3b805ca177a24ff78b466ca73febe8466c67ea61 (diff)
parent23b2c96fad21886c53f5e1a4ffedd45ddd2e85ba (diff)
Merge tag 'seccomp-v5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull seccomp updates from Kees Cook: "Mostly this is implementing the new flag SECCOMP_USER_NOTIF_FLAG_CONTINUE, but there are cleanups as well. - implement SECCOMP_USER_NOTIF_FLAG_CONTINUE (Christian Brauner) - fixes to selftests (Christian Brauner) - remove secure_computing() argument (Christian Brauner)" * tag 'seccomp-v5.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: seccomp: rework define for SECCOMP_USER_NOTIF_FLAG_CONTINUE seccomp: fix SECCOMP_USER_NOTIF_FLAG_CONTINUE test seccomp: simplify secure_computing() seccomp: test SECCOMP_USER_NOTIF_FLAG_CONTINUE seccomp: add SECCOMP_USER_NOTIF_FLAG_CONTINUE seccomp: avoid overflow in implicit constant conversion
Diffstat (limited to 'include')
-rw-r--r--include/linux/seccomp.h6
-rw-r--r--include/uapi/linux/seccomp.h29
2 files changed, 32 insertions, 3 deletions
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 84868d37b35d..03583b6d1416 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -33,10 +33,10 @@ struct seccomp {
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
extern int __secure_computing(const struct seccomp_data *sd);
-static inline int secure_computing(const struct seccomp_data *sd)
+static inline int secure_computing(void)
{
if (unlikely(test_thread_flag(TIF_SECCOMP)))
- return __secure_computing(sd);
+ return __secure_computing(NULL);
return 0;
}
#else
@@ -59,7 +59,7 @@ struct seccomp { };
struct seccomp_filter { };
#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
-static inline int secure_computing(struct seccomp_data *sd) { return 0; }
+static inline int secure_computing(void) { return 0; }
#else
static inline void secure_computing_strict(int this_syscall) { return; }
#endif
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index 90734aa5aa36..be84d87f1f46 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -76,6 +76,35 @@ struct seccomp_notif {
struct seccomp_data data;
};
+/*
+ * Valid flags for struct seccomp_notif_resp
+ *
+ * Note, the SECCOMP_USER_NOTIF_FLAG_CONTINUE flag must be used with caution!
+ * If set by the process supervising the syscalls of another process the
+ * syscall will continue. This is problematic because of an inherent TOCTOU.
+ * An attacker can exploit the time while the supervised process is waiting on
+ * a response from the supervising process to rewrite syscall arguments which
+ * are passed as pointers of the intercepted syscall.
+ * It should be absolutely clear that this means that the seccomp notifier
+ * _cannot_ be used to implement a security policy! It should only ever be used
+ * in scenarios where a more privileged process supervises the syscalls of a
+ * lesser privileged process to get around kernel-enforced security
+ * restrictions when the privileged process deems this safe. In other words,
+ * in order to continue a syscall the supervising process should be sure that
+ * another security mechanism or the kernel itself will sufficiently block
+ * syscalls if arguments are rewritten to something unsafe.
+ *
+ * Similar precautions should be applied when stacking SECCOMP_RET_USER_NOTIF
+ * or SECCOMP_RET_TRACE. For SECCOMP_RET_USER_NOTIF filters acting on the
+ * same syscall, the most recently added filter takes precedence. This means
+ * that the new SECCOMP_RET_USER_NOTIF filter can override any
+ * SECCOMP_IOCTL_NOTIF_SEND from earlier filters, essentially allowing all
+ * such filtered syscalls to be executed by sending the response
+ * SECCOMP_USER_NOTIF_FLAG_CONTINUE. Note that SECCOMP_RET_TRACE can equally
+ * be overriden by SECCOMP_USER_NOTIF_FLAG_CONTINUE.
+ */
+#define SECCOMP_USER_NOTIF_FLAG_CONTINUE (1UL << 0)
+
struct seccomp_notif_resp {
__u64 id;
__s64 val;