[PATCH v2] io_uring: reg buffer overflow checks hardening

[Pavel Begunkov <asml.silence@gmail.com>]

We are safe with overflows in io_sqe_buffer_register() because it will
just yield alloc failure, but it's nicer to check explicitly.

v2: replace u64 with ulong to handle 32 bit and match
    io_sqe_buffer_register() math. (Jens)

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f3ae83a2d7bc..f1a3dea05221 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8306,6 +8306,8 @@ static int io_buffers_map_alloc(struct io_ring_ctx *ctx, unsigned int nr_args)
 
 static int io_buffer_validate(struct iovec *iov)
 {
+	unsigned long tmp, acct_len = iov->iov_len + (PAGE_SIZE - 1);
+
 	/*
 	 * Don't impose further limits on the size and buffer
 	 * constraints here, we'll -EINVAL later when IO is
@@ -8318,6 +8320,9 @@ static int io_buffer_validate(struct iovec *iov)
 	if (iov->iov_len > SZ_1G)
 		return -EFAULT;
 
+	if (check_add_overflow((unsigned long)iov->iov_base, acct_len, &tmp))
+		return -EOVERFLOW;
+
 	return 0;
 }
 
-- 
2.24.0