From 1d0dbbfa282d9be57792e3b5827dc57b010181ee Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 18 May 2022 14:36:18 -0600
Subject: [PATCH] io_uring: initialize io_buffer_list head when shared ring is
unregistered
Git-commit: 1d0dbbfa282d9be57792e3b5827dc57b010181ee
Patch-mainline: v5.19-rc1
References: bsc#1205205
We use ->buf_pages != 0 to tell if this is a shared buffer ring or a
classic provided buffer group. If we unregister the shared ring and
then attempt to use it, buf_pages is zero yet the classic list head
isn't properly initialized. This causes io_buffer_select() to think
that we have classic buffers available, but then we crash when we try
and get one from the list.
Just initialize the list if we unregister a shared buffer ring, leaving
it in a sane state for either re-registration or for attempting to use
it. And do the same for the initial setup from the classic path.
Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
fs/io_uring.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a210a2c0429d..8fc3dd49bc04 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4969,6 +4969,8 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx,
kvfree(bl->buf_pages);
bl->buf_pages = NULL;
bl->buf_nr_pages = 0;
+ /* make sure it's seen as empty */
+ INIT_LIST_HEAD(&bl->buf_list);
return i;
}
@@ -5156,6 +5158,7 @@ static int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
ret = -ENOMEM;
goto err;
}
+ INIT_LIST_HEAD(&bl->buf_list);
ret = io_buffer_add_list(ctx, bl, p->bgid);
if (ret) {
kfree(bl);
--
2.35.3