2021-09-28 03:12:52

by 王贇

Subject: [RESEND PATCH v2] net: prevent user from passing illegal stab size

We observed below report when playing with netlink sock:

UBSAN: shift-out-of-bounds in net/sched/sch_api.c:580:10
shift exponent 249 is too large for 32-bit type
CPU: 0 PID: 685 Comm: a.out Not tainted
Call Trace:
dump_stack_lvl+0x8d/0xcf
ubsan_epilogue+0xa/0x4e
__ubsan_handle_shift_out_of_bounds+0x161/0x182
__qdisc_calculate_pkt_len+0xf0/0x190
__dev_queue_xmit+0x2ed/0x15b0

it seems like kernel won't check the stab log value passing from
user, and will use the insane value later to calculate pkt_len.

This patch just add a check on the size/cell_log to avoid insane
calculation.

Reported-by: Abaci <[email protected]>
Signed-off-by: Michael Wang <[email protected]>
---
include/net/pkt_sched.h | 1 +
net/sched/sch_api.c | 6 ++++++
2 files changed, 7 insertions(+)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 6d7b12c..bf79f3a 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -11,6 +11,7 @@
#include <uapi/linux/pkt_sched.h>

#define DEFAULT_TX_QUEUE_LEN 1000
+#define STAB_SIZE_LOG_MAX 30

struct qdisc_walker {
int stop;
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 5e90e9b..12f39a2 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -513,6 +513,12 @@ static struct qdisc_size_table *qdisc_get_stab(struct nlattr *opt,
return stab;
}

+ if (s->size_log > STAB_SIZE_LOG_MAX ||
+ s->cell_log > STAB_SIZE_LOG_MAX) {
+ NL_SET_ERR_MSG(extack, "Invalid logarithmic size of size table");
+ return ERR_PTR(-EINVAL);
+ }
+
stab = kmalloc(sizeof(*stab) + tsize * sizeof(u16), GFP_KERNEL);
if (!stab)
return ERR_PTR(-ENOMEM);
--
1.8.3.1

2021-09-28 05:14:17

by Cong Wang

Subject: Re: [RESEND PATCH v2] net: prevent user from passing illegal stab size

Hi,

It has been applied, no need to resend.

commit b193e15ac69d56f35e1d8e2b5d16cbd47764d053
Author: 王贇 <[email protected]>
AuthorDate: Fri Sep 24 10:35:58 2021 +0800
Commit: David S. Miller <[email protected]>
CommitDate: Sun Sep 26 11:09:07 2021 +0100

net: prevent user from passing illegal stab size

Thanks.

2021-09-28 05:35:45

by 王贇

Subject: Re: [RESEND PATCH v2] net: prevent user from passing illegal stab size

My bad... failed to get the notify, please ignore the noise.

Regards,
Michael Wang

On 2021/9/28 下午1:11, Cong Wang wrote:
> Hi,
>
> It has been applied, no need to resend.
>
> commit b193e15ac69d56f35e1d8e2b5d16cbd47764d053
> Author: 王贇 <[email protected]>
> AuthorDate: Fri Sep 24 10:35:58 2021 +0800
> Commit: David S. Miller <[email protected]>
> CommitDate: Sun Sep 26 11:09:07 2021 +0100
>
> net: prevent user from passing illegal stab size
>
> Thanks.
>