io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers
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>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7a2e83b..f46acbb 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -251,7 +251,7 @@
struct io_buffer {
struct list_head list;
__u64 addr;
- __s32 len;
+ __u32 len;
__u16 bid;
};
@@ -3986,7 +3986,7 @@
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++;
