io_uring: fix overflows checks in provide buffers

[ 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>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 55e214defb42f31981a3fe0cff4380760cc89552..369ec81033d6749a9f601b6ef65f88ad3830737d 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -527,7 +527,7 @@ struct io_splice {
 struct io_provide_buf {
        struct file                     *file;
        __u64                           addr;
-       __s32                           len;
+       __u32                           len;
        __u32                           bgid;
        __u16                           nbufs;
        __u16                           bid;
@@ -3996,7 +3996,7 @@ 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;
 
@@ -4010,6 +4010,12 @@ 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;