From: Thadeu Lima de Souza Cascardo cascardo@canonical.com

mainline inclusion from mainline-v5.13-rc1 commit d1f82808877bb10d3deee7cf3374a4eb3fb582db category: bugfix bugzilla: NA CVE: CVE-2021-3491

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Read and write operations are capped to MAX_RW_COUNT. Some read ops rely on that limit, and that is not guaranteed by the IORING_OP_PROVIDE_BUFFERS.

Truncate those lengths when doing io_add_buffers, so buffer addresses still use the uncapped length.

Also, take the chance and change struct io_buffer len member to __u32, so it matches struct io_provide_buffer len member.

This fixes CVE-2021-3491, also reported as ZDI-CAN-13546.

Fixes: ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS") Reported-by: Billy Jheng Bing-Jhong (@st424204) Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Reviewed-by: Zhang Yi yi.zhang@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/io_uring.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c index 02ebfc46228a9..f661231cdfad6 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -216,7 +216,7 @@ struct fixed_file_data { struct io_buffer { struct list_head list; __u64 addr; - __s32 len; + __u32 len; __u16 bid; };

@@ -3523,7 +3523,7 @@ static int io_add_buffers(struct io_provide_buf *pbuf, struct io_buffer **head) break;

buf->addr = addr; - buf->len = pbuf->len; + buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT); buf->bid = bid; addr += pbuf->len; bid++;