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io_uring: allow registering credentials

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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>
This commit is contained in:
Jens Axboe 2020-01-28 10:04:42 -07:00
parent 24369c2e3b
commit 071698e13a
2 changed files with 70 additions and 7 deletions
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75
fs/io_uring.c
View File

@ -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 @@ out:
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:

2
include/uapi/linux/io_uring.h
View File

@ -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;