Patch "net: prevent user from passing illegal stab size" has been added to the 5.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: prevent user from passing illegal stab size

to the 5.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-prevent-user-from-passing-illegal-stab-size.patch
and it can be found in the queue-5.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 88c9c0d29e391765497cf688085b70da4f63a868
Author: 王贇 <yun.wang@xxxxxxxxxxxxxxxxx>
Date:   Fri Sep 24 10:35:58 2021 +0800

    net: prevent user from passing illegal stab size
    
    [ Upstream commit b193e15ac69d56f35e1d8e2b5d16cbd47764d053 ]
    
    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 <abaci@xxxxxxxxxxxxxxxxx>
    Signed-off-by: Michael Wang <yun.wang@xxxxxxxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 6d7b12cba015..bf79f3a890af 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 f87d07736a14..148edd0e71e3 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);