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: Jiri Slaby <jslaby@suse.cz>

diff --git a/fs/aio.c b/fs/aio.c
index 307d7708dc00a64762ae08a2110087d12caca206..7bdf3467bf24f22a1c512f814b4ba1ce50023438 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -718,6 +718,9 @@ 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);