ioctx_alloc(): fix vma (and file) leak on failure

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@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@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 2f7e8c2e3e769c04f50b233c7f7f113b523e7e40..3241659491b1b80e78d133b04444c79b507dc0fe 100644 (file)
--- 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);