Commit 83a50840 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'seccomp-v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux 

Pull seccomp fixes from Kees Cook:
 "Syzbot found a use-after-free bug in seccomp due to flags that should
  not be allowed to be used together.

  Tycho fixed this, I updated the self-tests, and the syzkaller PoC has
  been running for several days without triggering KASan (before this
  fix, it would reproduce). These patches have also been in -next for
  almost a week, just to be sure.

   - Add logic for making some seccomp flags exclusive (Tycho)

   - Update selftests for exclusivity testing (Kees)"

* tag 'seccomp-v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  seccomp: Make NEW_LISTENER and TSYNC flags exclusive
  selftests/seccomp: Prepare for exclusive seccomp flags
parents 80871482 7a0df7fb

kernel/seccomp.c

+15 −2
Original line number Diff line number Diff line
@@ -502,7 +502,10 @@ out: 
 *

 * Caller must be holding current->sighand->siglock lock.

 *

 * Returns 0 on success, -ve on error.

 * Returns 0 on success, -ve on error, or

 *   - in TSYNC mode: the pid of a thread which was either not in the correct

 *     seccomp mode or did not have an ancestral seccomp filter

 *   - in NEW_LISTENER mode: the fd of the new listener

 */

static long seccomp_attach_filter(unsigned int flags,

				  struct seccomp_filter *filter)
@@ -1258,6 +1261,16 @@ static long seccomp_set_mode_filter(unsigned int flags, 
	if (flags & ~SECCOMP_FILTER_FLAG_MASK)

		return -EINVAL;



	/*

	 * In the successful case, NEW_LISTENER returns the new listener fd.

	 * But in the failure case, TSYNC returns the thread that died. If you

	 * combine these two flags, there's no way to tell whether something

	 * succeeded or failed. So, let's disallow this combination.

	 */

	if ((flags & SECCOMP_FILTER_FLAG_TSYNC) &&

	    (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER))

		return -EINVAL;



	/* Prepare the new filter before holding any locks. */

	prepared = seccomp_prepare_user_filter(filter);

	if (IS_ERR(prepared))
@@ -1304,7 +1317,7 @@ out: 
		mutex_unlock(&current->signal->cred_guard_mutex);

out_put_fd:

	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {

		if (ret < 0) {

		if (ret) {

			listener_f->private_data = NULL;

			fput(listener_f);

			put_unused_fd(listener);

tools/testing/selftests/seccomp/seccomp_bpf.c

+25 −9
Original line number Diff line number Diff line
@@ -2166,11 +2166,14 @@ TEST(detect_seccomp_filter_flags) 
				 SECCOMP_FILTER_FLAG_LOG,

				 SECCOMP_FILTER_FLAG_SPEC_ALLOW,

				 SECCOMP_FILTER_FLAG_NEW_LISTENER };

	unsigned int flag, all_flags;

	unsigned int exclusive[] = {

				SECCOMP_FILTER_FLAG_TSYNC,

				SECCOMP_FILTER_FLAG_NEW_LISTENER };

	unsigned int flag, all_flags, exclusive_mask;

	int i;

	long ret;



	/* Test detection of known-good filter flags */

	/* Test detection of individual known-good filter flags */

	for (i = 0, all_flags = 0; i < ARRAY_SIZE(flags); i++) {

		int bits = 0;
@@ -2197,16 +2200,29 @@ TEST(detect_seccomp_filter_flags) 
		all_flags |= flag;

	}



	/* Test detection of all known-good filter flags */

	ret = seccomp(SECCOMP_SET_MODE_FILTER, all_flags, NULL);

	/*

	 * Test detection of all known-good filter flags combined. But

	 * for the exclusive flags we need to mask them out and try them

	 * individually for the "all flags" testing.

	 */

	exclusive_mask = 0;

	for (i = 0; i < ARRAY_SIZE(exclusive); i++)

		exclusive_mask |= exclusive[i];

	for (i = 0; i < ARRAY_SIZE(exclusive); i++) {

		flag = all_flags & ~exclusive_mask;

		flag |= exclusive[i];



		ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);

		EXPECT_EQ(-1, ret);

		EXPECT_EQ(EFAULT, errno) {

			TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!",

		       all_flags);

			       flag);

		}

	}



	/* Test detection of an unknown filter flag */

	/* Test detection of an unknown filter flags, without exclusives. */

	flag = -1;

	flag &= ~exclusive_mask;

	ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);

	EXPECT_EQ(-1, ret);

	EXPECT_EQ(EINVAL, errno) {

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