[PATCH 5.11 382/601] io_uring: fix overflows checks in provide buffers

Greg Kroah-Hartman
2021-05-12T17:41:44Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit 38134ada0ceea3e848fe993263c0ff6207fd46e7 ]

Colin reported before possible overflow and sign extension problems in
io_provide_buffers_prep(). As Linus pointed out previous attempt did nothing
useful, see d81269fecb8ce ("io_uring: fix provide_buffers sign extension").

Do that with help of check_<op>_overflow helpers. And fix struct
io_provide_buf::len type, as it doesn't make much sense to keep it
signed.

Reported-by: Colin Ian King <colin.king@canonical.com>
Fixes: efe68c1ca8f49 ("io_uring: validate the full range of provided buffers for access")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/46538827e70fce5f6cdb50897cff4cacc490f380.1618488258.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 157ceda04650..c42c2e9570e5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -535,7 +535,7 @@ struct io_splice {
struct io_provide_buf {
struct file *file;
__u64 addr;
- __s32 len;
+ __u32 len;
__u32 bgid;
__u16 nbufs;
__u16 bid;
@@ -4214,7 +4214,7 @@ static int io_remove_buffers(struct io_kiocb *req, bool force_nonblock,
static int io_provide_buffers_prep(struct io_kiocb *req,
const struct io_uring_sqe *sqe)
{
- unsigned long size;
+ unsigned long size, tmp_check;
struct io_provide_buf *p = &req->pbuf;
u64 tmp;

@@ -4228,6 +4228,12 @@ static int io_provide_buffers_prep(struct io_kiocb *req,
p->addr = READ_ONCE(sqe->addr);
p->len = READ_ONCE(sqe->len);

+ if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
+ &size))
+ return -EOVERFLOW;
+ if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
+ return -EOVERFLOW;
+
size = (unsigned long)p->len * p->nbufs;
if (!access_ok(u64_to_user_ptr(p->addr), size))
return -EFAULT;
--
2.30.2