2021-03-22 18:44:45

by Muhammad Usama Anjum

Subject: [PATCH] io_uring: Initialize variable before use

1) Initialize the struct msghdr msg in the start of the function
2) Uninitialized variable msg.msg_flags can get used if branch happens to
out_free before initialization.

So initialize variable in question in the start of the function for
simplicity in logic and use.

Addresses-Coverity: ("Uninitialized variable")
Addresses-Coverity: ("Uninitialized variable read")
Signed-off-by: Muhammad Usama Anjum <[email protected]>
---
fs/io_uring.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index bba74631954b..d5f83326abff 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4677,7 +4677,8 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
{
struct io_buffer *kbuf;
struct io_sr_msg *sr = &req->sr_msg;
- struct msghdr msg;
+ struct msghdr msg = {.msg_name = NULL, .msg_control = NULL, .msg_controllen = 0,
+ .msg_namelen = 0, .msg_iocb = NULL, .msg_flags = 0};
void __user *buf = sr->buf;
struct socket *sock;
struct iovec iov;
@@ -4701,13 +4702,6 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
if (unlikely(ret))
goto out_free;

- msg.msg_name = NULL;
- msg.msg_control = NULL;
- msg.msg_controllen = 0;
- msg.msg_namelen = 0;
- msg.msg_iocb = NULL;
- msg.msg_flags = 0;
-
flags = req->sr_msg.msg_flags | MSG_NOSIGNAL;
if (flags & MSG_DONTWAIT)
req->flags |= REQ_F_NOWAIT;
--
2.25.1

2021-03-31 08:27:19

by Muhammad Usama Anjum

Subject: Re: [PATCH] io_uring: Initialize variable before use

On Mon, 2021-03-22 at 23:41 +0500, Muhammad Usama Anjum wrote:
> 1) Initialize the struct msghdr msg in the start of the function
> 2) Uninitialized variable msg.msg_flags can get used if branch happens to
> out_free before initialization.
>
> So initialize variable in question in the start of the function for
> simplicity in logic and use.
>
> Addresses-Coverity: ("Uninitialized variable")
> Addresses-Coverity: ("Uninitialized variable read")
> Signed-off-by: Muhammad Usama Anjum <[email protected]>
> ---
> fs/io_uring.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index bba74631954b..d5f83326abff 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4677,7 +4677,8 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
> {
> struct io_buffer *kbuf;
> struct io_sr_msg *sr = &req->sr_msg;
> - struct msghdr msg;
> + struct msghdr msg = {.msg_name = NULL, .msg_control = NULL, .msg_controllen = 0,
> + .msg_namelen = 0, .msg_iocb = NULL, .msg_flags = 0};
> void __user *buf = sr->buf;
> struct socket *sock;
> struct iovec iov;
> @@ -4701,13 +4702,6 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
> if (unlikely(ret))
> goto out_free;
>
> - msg.msg_name = NULL;
> - msg.msg_control = NULL;
> - msg.msg_controllen = 0;
> - msg.msg_namelen = 0;
> - msg.msg_iocb = NULL;
> - msg.msg_flags = 0;
> -
> flags = req->sr_msg.msg_flags | MSG_NOSIGNAL;
> if (flags & MSG_DONTWAIT)
> req->flags |= REQ_F_NOWAIT;

Reminder. Does anybody has any comments on it?

2021-03-31 08:50:27

by Dan Carpenter

Subject: Re: [PATCH] io_uring: Initialize variable before use

On Mon, Mar 22, 2021 at 11:41:58PM +0500, Muhammad Usama Anjum wrote:
> 1) Initialize the struct msghdr msg in the start of the function
> 2) Uninitialized variable msg.msg_flags can get used if branch happens to
> out_free before initialization.
>
> So initialize variable in question in the start of the function for
> simplicity in logic and use.
>
> Addresses-Coverity: ("Uninitialized variable")
> Addresses-Coverity: ("Uninitialized variable read")

This bug is a false positive.

When msg.msg_flags is uninitialized then ret is negative and min_ret is
zero.

fs/io_uring.c
4666 ret = -EINTR;
4667 out_free:
4668 if (req->flags & REQ_F_BUFFER_SELECTED)
4669 cflags = io_put_recv_kbuf(req);
4670 if (ret < min_ret || ((flags & MSG_WAITALL) && (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))))
^^^^^^^^^^^^^ ^^^^^^^^^^^^^
The first part of the condition is true so the second part is not used.

4671 req_set_fail_links(req);
4672 __io_req_complete(req, issue_flags, ret, cflags);
4673 return 0;
4674 }

regards,
dan carpenter

2021-03-31 10:01:08

by Muhammad Usama Anjum

Subject: Re: [PATCH] io_uring: Initialize variable before use

On Wed, 2021-03-31 at 11:48 +0300, Dan Carpenter wrote:
> On Mon, Mar 22, 2021 at 11:41:58PM +0500, Muhammad Usama Anjum wrote:
> > 1) Initialize the struct msghdr msg in the start of the function
> > 2) Uninitialized variable msg.msg_flags can get used if branch happens to
> > out_free before initialization.
> >
> > So initialize variable in question in the start of the function for
> > simplicity in logic and use.
> >
> > Addresses-Coverity: ("Uninitialized variable")
> > Addresses-Coverity: ("Uninitialized variable read")
>
> This bug is a false positive.
>
> When msg.msg_flags is uninitialized then ret is negative and min_ret is
> zero.
>
> fs/io_uring.c
> 4666 ret = -EINTR;
> 4667 out_free:
> 4668 if (req->flags & REQ_F_BUFFER_SELECTED)
> 4669 cflags = io_put_recv_kbuf(req);
> 4670 if (ret < min_ret || ((flags & MSG_WAITALL) && (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC))))
> ^^^^^^^^^^^^^ ^^^^^^^^^^^^^
> The first part of the condition is true so the second part is not used.
>
> 4671 req_set_fail_links(req);
> 4672 __io_req_complete(req, issue_flags, ret, cflags);
> 4673 return 0;
> 4674 }
>
Understood. Thank you so much!

Thanks,
Usama

> regards,
> dan carpenter
>