linux-kernel - Re: [bpf, xdp] headroom - was: Re: Question about to KMSAN: uninit-value in can

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Message-ID: <20260102120405.34613b68@kernel.org>
Date: Fri, 2 Jan 2026 12:04:05 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Prithvi <activprithvi@...il.com>
Cc: andrii@...nel.org, socketcan@...tkopp.net, mkl@...gutronix.de,
 linux-can@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzkaller-bugs@...glegroups.com, netdev@...r.kernel.org
Subject: Re: [bpf, xdp] headroom - was: Re: Question about to KMSAN:
 uninit-value in can_receive

On Fri, 2 Jan 2026 21:06:11 +0530 Prithvi wrote:
> Just a gentle ping on this thread 

You're asking the wrong person, IIUC Andrii is tangentially involved
in XDP (via bpf links?):

XDP (eXpress Data Path)
M:	Alexei Starovoitov <ast@...nel.org>
M:	Daniel Borkmann <daniel@...earbox.net>
M:	David S. Miller <davem@...emloft.net>
M:	Jakub Kicinski <kuba@...nel.org>
M:	Jesper Dangaard Brouer <hawk@...nel.org>
M:	John Fastabend <john.fastabend@...il.com>
R:	Stanislav Fomichev <sdf@...ichev.me>
L:	netdev@...r.kernel.org
L:	bpf@...r.kernel.org

Without looking too deeply - XDP has historically left the new space
uninitialized after push, expecting programs to immediately write the
headers in that space. syzbot had run into this in the past but I can't
find any references to past threads quickly :(