/*
 * memfd GUP test-case
 * This tests memfd interactions with get_user_pages(). We require the
 * fuse_mnt.c program to provide a fake direct-IO FUSE mount-point for us. This
 * file-system delays _all_ reads by 1s and forces direct-IO. This means, any
 * read() on files in that file-system will pin the receive-buffer pages for at
 * least 1s via get_user_pages().
 *
 * We use this trick to race ADD_SEALS against a write on a memfd object. The
 * ADD_SEALS must fail if the memfd pages are still pinned. Note that we use
 * the read() syscall with our memory-mapped memfd object as receive buffer to
 * force the kernel to write into our memfd object.
 */

#define _GNU_SOURCE
#define __EXPORTED_HEADERS__

#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <linux/falloc.h>
#include <linux/fcntl.h>
#include <linux/memfd.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>

#define MFD_DEF_SIZE 8192
#define STACK_SIZE 65535

static int sys_memfd_create(const char *name,
			    unsigned int flags)
{
	return syscall(__NR_memfd_create, name, flags);
}

static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
{
	int r, fd;

	fd = sys_memfd_create(name, flags);
	if (fd < 0) {
		printf("memfd_create(\"%s\", %u) failed: %m\n",
		       name, flags);
		abort();
	}

	r = ftruncate(fd, sz);
	if (r < 0) {
		printf("ftruncate(%llu) failed: %m\n", (unsigned long long)sz);
		abort();
	}

	return fd;
}

static __u64 mfd_assert_get_seals(int fd)
{
	long r;

	r = fcntl(fd, F_GET_SEALS);
	if (r < 0) {
		printf("GET_SEALS(%d) failed: %m\n", fd);
		abort();
	}

	return r;
}

static void mfd_assert_has_seals(int fd, __u64 seals)
{
	__u64 s;

	s = mfd_assert_get_seals(fd);
	if (s != seals) {
		printf("%llu != %llu = GET_SEALS(%d)\n",
		       (unsigned long long)seals, (unsigned long long)s, fd);
		abort();
	}
}

static void mfd_assert_add_seals(int fd, __u64 seals)
{
	long r;
	__u64 s;

	s = mfd_assert_get_seals(fd);
	r = fcntl(fd, F_ADD_SEALS, seals);
	if (r < 0) {
		printf("ADD_SEALS(%d, %llu -> %llu) failed: %m\n",
		       fd, (unsigned long long)s, (unsigned long long)seals);
		abort();
	}
}

static int mfd_busy_add_seals(int fd, __u64 seals)
{
	long r;
	__u64 s;

	r = fcntl(fd, F_GET_SEALS);
	if (r < 0)
		s = 0;
	else
		s = r;

	r = fcntl(fd, F_ADD_SEALS, seals);
	if (r < 0 && errno != EBUSY) {
		printf("ADD_SEALS(%d, %llu -> %llu) didn't fail as expected with EBUSY: %m\n",
		       fd, (unsigned long long)s, (unsigned long long)seals);
		abort();
	}

	return r;
}

static void *mfd_assert_mmap_shared(int fd)
{
	void *p;

	p = mmap(NULL,
		 MFD_DEF_SIZE,
		 PROT_READ | PROT_WRITE,
		 MAP_SHARED,
		 fd,
		 0);
	if (p == MAP_FAILED) {
		printf("mmap() failed: %m\n");
		abort();
	}

	return p;
}

static void *mfd_assert_mmap_private(int fd)
{
	void *p;

	p = mmap(NULL,
		 MFD_DEF_SIZE,
		 PROT_READ | PROT_WRITE,
		 MAP_PRIVATE,
		 fd,
		 0);
	if (p == MAP_FAILED) {
		printf("mmap() failed: %m\n");
		abort();
	}

	return p;
}

static int global_mfd = -1;
static void *global_p = NULL;

static int sealing_thread_fn(void *arg)
{
	int sig, r;

	/*
	 * This thread first waits 200ms so any pending operation in the parent
	 * is correctly started. After that, it tries to seal @global_mfd as
	 * SEAL_WRITE. This _must_ fail as the parent thread has a read() into
	 * that memory mapped object still ongoing.
	 * We then wait one more second and try sealing again. This time it
	 * must succeed as there shouldn't be anyone else pinning the pages.
	 */

	/* wait 200ms for FUSE-request to be active */
	usleep(200000);

	/* unmount mapping before sealing to avoid i_mmap_writable failures */
	munmap(global_p, MFD_DEF_SIZE);

	/* Try sealing the global file; expect EBUSY or success. Current
	 * kernels will never succeed, but in the future, kernels might
	 * implement page-replacements or other fancy ways to avoid racing
	 * writes. */
	r = mfd_busy_add_seals(global_mfd, F_SEAL_WRITE);
	if (r >= 0) {
		printf("HURRAY! This kernel fixed GUP races!\n");
	} else {
		/* wait 1s more so the FUSE-request is done */
		sleep(1);

		/* try sealing the global file again */
		mfd_assert_add_seals(global_mfd, F_SEAL_WRITE);
	}

	return 0;
}

static pid_t spawn_sealing_thread(void)
{
	uint8_t *stack;
	pid_t pid;

	stack = malloc(STACK_SIZE);
	if (!stack) {
		printf("malloc(STACK_SIZE) failed: %m\n");
		abort();
	}

	pid = clone(sealing_thread_fn,
		    stack + STACK_SIZE,
		    SIGCHLD | CLONE_FILES | CLONE_FS | CLONE_VM,
		    NULL);
	if (pid < 0) {
		printf("clone() failed: %m\n");
		abort();
	}

	return pid;
}

static void join_sealing_thread(pid_t pid)
{
	waitpid(pid, NULL, 0);
}

int main(int argc, char **argv)
{
	static const char zero[MFD_DEF_SIZE];
	int fd, mfd, r;
	void *p;
	int was_sealed;
	pid_t pid;

	if (argc < 2) {
		printf("error: please pass path to file in fuse_mnt mount-point\n");
		abort();
	}

	/* open FUSE memfd file for GUP testing */
	printf("opening: %s\n", argv[1]);
	fd = open(argv[1], O_RDONLY | O_CLOEXEC);
	if (fd < 0) {
		printf("cannot open(\"%s\"): %m\n", argv[1]);
		abort();
	}

	/* create new memfd-object */
	mfd = mfd_assert_new("kern_memfd_fuse",
			     MFD_DEF_SIZE,
			     MFD_CLOEXEC | MFD_ALLOW_SEALING);

	/* mmap memfd-object for writing */
	p = mfd_assert_mmap_shared(mfd);

	/* pass mfd+mapping to a separate sealing-thread which tries to seal
	 * the memfd objects with SEAL_WRITE while we write into it */
	global_mfd = mfd;
	global_p = p;
	pid = spawn_sealing_thread();

	/* Use read() on the FUSE file to read into our memory-mapped memfd
	 * object. This races the other thread which tries to seal the
	 * memfd-object.
	 * If @fd is on the memfd-fake-FUSE-FS, the read() is delayed by 1s.
	 * This guarantees that the receive-buffer is pinned for 1s until the
	 * data is written into it. The racing ADD_SEALS should thus fail as
	 * the pages are still pinned. */
	r = read(fd, p, MFD_DEF_SIZE);
	if (r < 0) {
		printf("read() failed: %m\n");
		abort();
	} else if (!r) {
		printf("unexpected EOF on read()\n");
		abort();
	}

	was_sealed = mfd_assert_get_seals(mfd) & F_SEAL_WRITE;

	/* Wait for sealing-thread to finish and verify that it
	 * successfully sealed the file after the second try. */
	join_sealing_thread(pid);
	mfd_assert_has_seals(mfd, F_SEAL_WRITE);

	/* *IF* the memfd-object was sealed at the time our read() returned,
	 * then the kernel did a page-replacement or canceled the read() (or
	 * whatever magic it did..). In that case, the memfd object is still
	 * all zero.
	 * In case the memfd-object was *not* sealed, the read() was successfull
	 * and the memfd object must *not* be all zero.
	 * Note that in real scenarios, there might be a mixture of both, but
	 * in this test-cases, we have explicit 200ms delays which should be
	 * enough to avoid any in-flight writes. */

	p = mfd_assert_mmap_private(mfd);
	if (was_sealed && memcmp(p, zero, MFD_DEF_SIZE)) {
		printf("memfd sealed during read() but data not discarded\n");
		abort();
	} else if (!was_sealed && !memcmp(p, zero, MFD_DEF_SIZE)) {
		printf("memfd sealed after read() but data discarded\n");
		abort();
	}

	close(mfd);
	close(fd);

	printf("fuse: DONE\n");

	return 0;
}
3/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'sound/soc/ux500/ux500_msp_i2s.h')</div><table summary='diffstat' class='diffstat'>