This is a note to let you know that I've just added the patch titled
drivers: net: prevent tun_build_skb() to exceed the packet size limit
to the 5.15-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:
drivers-net-prevent-tun_build_skb-to-exceed-the-packet-size-limit.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 59eeb232940515590de513b997539ef495faca9a Mon Sep 17 00:00:00 2001
From: Andrew Kanner <andrew.kanner@xxxxxxxxx>
Date: Thu, 3 Aug 2023 20:59:48 +0200
Subject: drivers: net: prevent tun_build_skb() to exceed the packet size limit
From: Andrew Kanner <andrew.kanner@xxxxxxxxx>
commit 59eeb232940515590de513b997539ef495faca9a upstream.
Using the syzkaller repro with reduced packet size it was discovered
that XDP_PACKET_HEADROOM is not checked in tun_can_build_skb(),
although pad may be incremented in tun_build_skb(). This may end up
with exceeding the PAGE_SIZE limit in tun_build_skb().
Jason Wang <jasowang@xxxxxxxxxx> proposed to count XDP_PACKET_HEADROOM
always (e.g. without rcu_access_pointer(tun->xdp_prog)) in
tun_can_build_skb() since there's a window during which XDP program
might be attached between tun_can_build_skb() and tun_build_skb().
Fixes: 7df13219d757 ("tun: reserve extra headroom only when XDP is set")
Link: https://syzkaller.appspot.com/bug?extid=f817490f5bd20541b90a
Signed-off-by: Andrew Kanner <andrew.kanner@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230803185947.2379988-1-andrew.kanner@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/tun.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1574,7 +1574,7 @@ static bool tun_can_build_skb(struct tun
if (zerocopy)
return false;
- if (SKB_DATA_ALIGN(len + TUN_RX_PAD) +
+ if (SKB_DATA_ALIGN(len + TUN_RX_PAD + XDP_PACKET_HEADROOM) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) > PAGE_SIZE)
return false;
Patches currently in stable-queue which might be from andrew.kanner@xxxxxxxxx are
queue-5.15/net-core-remove-unnecessary-frame_sz-check-in-bpf_xdp_adjust_tail.patch
queue-5.15/drivers-net-prevent-tun_build_skb-to-exceed-the-packet-size-limit.patch
