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

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>
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/aio.c b/fs/aio.c
index 58c33dcfb6caf4a668ae24cc6512c6385113243f..a793f7023755dc15cb2b8bebe5206bc610bb428c 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -731,6 +731,9 @@ 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);