io_uring: allow registering credentials
If an application wants to use a ring with different kinds of
credentials, it can register them upfront. We don't lookup credentials,
the credentials of the task calling IORING_REGISTER_PERSONALITY is used.
An 'id' is returned for the application to use in subsequent personality
support.
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 275355b..d74567f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -273,6 +273,8 @@ struct io_ring_ctx {
struct socket *ring_sock;
#endif
+ struct idr personality_idr;
+
struct {
unsigned cached_cq_tail;
unsigned cq_entries;
@@ -796,6 +798,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_LIST_HEAD(&ctx->cq_overflow_list);
init_completion(&ctx->completions[0]);
init_completion(&ctx->completions[1]);
+ idr_init(&ctx->personality_idr);
mutex_init(&ctx->uring_lock);
init_waitqueue_head(&ctx->wait);
spin_lock_init(&ctx->completion_lock);
@@ -6177,6 +6180,17 @@ static int io_uring_fasync(int fd, struct file *file, int on)
return fasync_helper(fd, file, on, &ctx->cq_fasync);
}
+static int io_remove_personalities(int id, void *p, void *data)
+{
+ struct io_ring_ctx *ctx = data;
+ const struct cred *cred;
+
+ cred = idr_remove(&ctx->personality_idr, id);
+ if (cred)
+ put_cred(cred);
+ return 0;
+}
+
static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
{
mutex_lock(&ctx->uring_lock);
@@ -6193,6 +6207,7 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
/* if we failed setting up the ctx, we might not have any rings */
if (ctx->rings)
io_cqring_overflow_flush(ctx, true);
+ idr_for_each(&ctx->personality_idr, io_remove_personalities, ctx);
wait_for_completion(&ctx->completions[0]);
io_ring_ctx_free(ctx);
}
@@ -6683,6 +6698,45 @@ static int io_probe(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
return ret;
}
+static int io_register_personality(struct io_ring_ctx *ctx)
+{
+ const struct cred *creds = get_current_cred();
+ int id;
+
+ id = idr_alloc_cyclic(&ctx->personality_idr, (void *) creds, 1,
+ USHRT_MAX, GFP_KERNEL);
+ if (id < 0)
+ put_cred(creds);
+ return id;
+}
+
+static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
+{
+ const struct cred *old_creds;
+
+ old_creds = idr_remove(&ctx->personality_idr, id);
+ if (old_creds) {
+ put_cred(old_creds);
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+static bool io_register_op_must_quiesce(int op)
+{
+ switch (op) {
+ case IORING_UNREGISTER_FILES:
+ case IORING_REGISTER_FILES_UPDATE:
+ case IORING_REGISTER_PROBE:
+ case IORING_REGISTER_PERSONALITY:
+ case IORING_UNREGISTER_PERSONALITY:
+ return false;
+ default:
+ return true;
+ }
+}
+
static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
void __user *arg, unsigned nr_args)
__releases(ctx->uring_lock)
@@ -6698,9 +6752,7 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (percpu_ref_is_dying(&ctx->refs))
return -ENXIO;
- if (opcode != IORING_UNREGISTER_FILES &&
- opcode != IORING_REGISTER_FILES_UPDATE &&
- opcode != IORING_REGISTER_PROBE) {
+ if (io_register_op_must_quiesce(opcode)) {
percpu_ref_kill(&ctx->refs);
/*
@@ -6768,15 +6820,24 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
break;
ret = io_probe(ctx, arg, nr_args);
break;
+ case IORING_REGISTER_PERSONALITY:
+ ret = -EINVAL;
+ if (arg || nr_args)
+ break;
+ ret = io_register_personality(ctx);
+ break;
+ case IORING_UNREGISTER_PERSONALITY:
+ ret = -EINVAL;
+ if (arg)
+ break;
+ ret = io_unregister_personality(ctx, nr_args);
+ break;
default:
ret = -EINVAL;
break;
}
-
- if (opcode != IORING_UNREGISTER_FILES &&
- opcode != IORING_REGISTER_FILES_UPDATE &&
- opcode != IORING_REGISTER_PROBE) {
+ if (io_register_op_must_quiesce(opcode)) {
/* bring the ctx back to life */
percpu_ref_reinit(&ctx->refs);
out:
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index e067b92..b4ccf31 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -211,6 +211,8 @@ struct io_uring_params {
#define IORING_REGISTER_FILES_UPDATE 6
#define IORING_REGISTER_EVENTFD_ASYNC 7
#define IORING_REGISTER_PROBE 8
+#define IORING_REGISTER_PERSONALITY 9
+#define IORING_UNREGISTER_PERSONALITY 10
struct io_uring_files_update {
__u32 offset;
