From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
You can't call idr_remove() from within a idr_for_each() callback,
but you can call xa_erase() from an xa_for_each() loop, so switch the
entire personality_idr from the IDR to the XArray. This manifests as a
use-after-free as idr_for_each() attempts to walk the rest of the node
after removing the last entry from it.
Fixes: 071698e13ac6 ("io_uring: allow registering credentials")
Cc: stable@xxxxxxxxxxxxxxx # 5.6+
Reported-by: yangerkun <yangerkun@xxxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
[Pavel: rebased (creds load was moved into io_init_req())]
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/7ccff36e1375f2b0ebf73d957f037b43becc0dde.1615212806.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/io_uring.c | 47 ++++++++++++++++++++++++-----------------------
1 file changed, 24 insertions(+), 23 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3f6db813d670..84eb499368a4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -406,7 +406,8 @@ struct io_ring_ctx {
struct idr io_buffer_idr;
- struct idr personality_idr;
+ struct xarray personalities;
+ u32 pers_next;
struct {
unsigned cached_cq_tail;
@@ -1137,7 +1138,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
init_completion(&ctx->ref_comp);
init_completion(&ctx->sq_thread_comp);
idr_init(&ctx->io_buffer_idr);
- idr_init(&ctx->personality_idr);
+ xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
mutex_init(&ctx->uring_lock);
init_waitqueue_head(&ctx->wait);
spin_lock_init(&ctx->completion_lock);
@@ -6337,7 +6338,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
req->work.list.next = NULL;
personality = READ_ONCE(sqe->personality);
if (personality) {
- req->work.creds = idr_find(&ctx->personality_idr, personality);
+ req->work.creds = xa_load(&ctx->personalities, personality);
if (!req->work.creds)
return -EINVAL;
get_cred(req->work.creds);
@@ -8355,7 +8356,6 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
mutex_unlock(&ctx->uring_lock);
io_eventfd_unregister(ctx);
io_destroy_buffers(ctx);
- idr_destroy(&ctx->personality_idr);
#if defined(CONFIG_UNIX)
if (ctx->ring_sock) {
@@ -8420,7 +8420,7 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
{
const struct cred *creds;
- creds = idr_remove(&ctx->personality_idr, id);
+ creds = xa_erase(&ctx->personalities, id);
if (creds) {
put_cred(creds);
return 0;
@@ -8429,14 +8429,6 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
return -EINVAL;
}
-static int io_remove_personalities(int id, void *p, void *data)
-{
- struct io_ring_ctx *ctx = data;
-
- io_unregister_personality(ctx, id);
- return 0;
-}
-
static bool io_run_ctx_fallback(struct io_ring_ctx *ctx)
{
struct callback_head *work, *next;
@@ -8526,13 +8518,17 @@ static void io_ring_exit_work(struct work_struct *work)
static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
{
+ unsigned long index;
+ struct creds *creds;
+
mutex_lock(&ctx->uring_lock);
percpu_ref_kill(&ctx->refs);
/* if force is set, the ring is going away. always drop after that */
ctx->cq_overflow_flushed = 1;
if (ctx->rings)
__io_cqring_overflow_flush(ctx, true, NULL, NULL);
- idr_for_each(&ctx->personality_idr, io_remove_personalities, ctx);
+ xa_for_each(&ctx->personalities, index, creds)
+ io_unregister_personality(ctx, index);
mutex_unlock(&ctx->uring_lock);
io_kill_timeouts(ctx, NULL, NULL);
@@ -9162,10 +9158,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
}
#ifdef CONFIG_PROC_FS
-static int io_uring_show_cred(int id, void *p, void *data)
+static int io_uring_show_cred(struct seq_file *m, unsigned int id,
+ const struct cred *cred)
{
- const struct cred *cred = p;
- struct seq_file *m = data;
struct user_namespace *uns = seq_user_ns(m);
struct group_info *gi;
kernel_cap_t cap;
@@ -9233,9 +9228,13 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf,
(unsigned int) buf->len);
}
- if (has_lock && !idr_is_empty(&ctx->personality_idr)) {
+ if (has_lock && !xa_empty(&ctx->personalities)) {
+ unsigned long index;
+ const struct cred *cred;
+
seq_printf(m, "Personalities:\n");
- idr_for_each(&ctx->personality_idr, io_uring_show_cred, m);
+ xa_for_each(&ctx->personalities, index, cred)
+ io_uring_show_cred(m, index, cred);
}
seq_printf(m, "PollList:\n");
spin_lock_irq(&ctx->completion_lock);
@@ -9564,14 +9563,16 @@ static int io_probe(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
static int io_register_personality(struct io_ring_ctx *ctx)
{
const struct cred *creds;
+ u32 id;
int ret;
creds = get_current_cred();
- ret = idr_alloc_cyclic(&ctx->personality_idr, (void *) creds, 1,
- USHRT_MAX, GFP_KERNEL);
- if (ret < 0)
- put_cred(creds);
+ ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)creds,
+ XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL);
+ if (!ret)
+ return id;
+ put_cred(creds);
return ret;
}
--
2.30.2
