[PATCH 3.16.y-ckt 020/180] ioctx_alloc(): fix vma (and file) leak on failure

[Luis Henriques]

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro at zeniv.linux.org.uk>

commit deeb8525f9bcea60f5e86521880c1161de7a5829 upstream.

If we fail past the aio_setup_ring(), we need to destroy the
mapping.  We don't need to care about anybody having found ctx,
or added requests to it, since the last failure exit is exactly
the failure to make ctx visible to lookups.

Reproducer (based on one by Joe Mario <jmario at redhat.com>):

void count(char *p)
{
	char s[80];
	printf("%s: ", p);
	fflush(stdout);
	sprintf(s, "/bin/cat /proc/%d/maps|/bin/fgrep -c '/[aio] (deleted)'", getpid());
	system(s);
}

int main()
{
	io_context_t *ctx;
	int created, limit, i, destroyed;
	FILE *f;

	count("before");
	if ((f = fopen("/proc/sys/fs/aio-max-nr", "r")) == NULL)
		perror("opening aio-max-nr");
	else if (fscanf(f, "%d", &limit) != 1)
		fprintf(stderr, "can't parse aio-max-nr\n");
	else if ((ctx = calloc(limit, sizeof(io_context_t))) == NULL)
		perror("allocating aio_context_t array");
	else {
		for (i = 0, created = 0; i < limit; i++) {
			if (io_setup(1000, ctx + created) == 0)
				created++;
		}
		for (i = 0, destroyed = 0; i < created; i++)
			if (io_destroy(ctx[i]) == 0)
				destroyed++;
		printf("created %d, failed %d, destroyed %d\n",
			created, limit - created, destroyed);
		count("after");
	}
}

Found-by: Joe Mario <jmario at redhat.com>
Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/aio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index b645387b6d57..a6f86dae34be 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -719,6 +719,9 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
 err_cleanup:
 	aio_nr_sub(ctx->max_reqs);
 err_ctx:
+	atomic_set(&ctx->dead, 1);
+	if (ctx->mmap_size)
+		vm_munmap(ctx->mmap_base, ctx->mmap_size);
 	aio_free_ring(ctx);
 err:
 	mutex_unlock(&ctx->ring_lock);