Messages in this thread Patch in this message | | | Date | Tue, 27 Jul 2021 17:43:18 +0300 | From | Pavel Skripkin <> | Subject | Re: [syzbot] UBSAN: shift-out-of-bounds in xfrm_set_default |
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On Tue, 27 Jul 2021 05:47:21 -0700 syzbot <syzbot+9cd5837a045bbee5b810@syzkaller.appspotmail.com> wrote:
> Hello, > > syzbot found the following issue on: > > HEAD commit: 90d856e71443 Add linux-next specific files for > 20210723 git tree: linux-next > console output: > https://syzkaller.appspot.com/x/log.txt?x=133fd00a300000 kernel > config: https://syzkaller.appspot.com/x/.config?x=298516715f6ad5cd > dashboard link: > https://syzkaller.appspot.com/bug?extid=9cd5837a045bbee5b810 > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU > Binutils for Debian) 2.35.1 syz repro: > https://syzkaller.appspot.com/x/repro.syz?x=1263bba6300000 C > reproducer: https://syzkaller.appspot.com/x/repro.c?x=1066b4d4300000 > > IMPORTANT: if you fix the issue, please add the following tag to the > commit: Reported-by: > syzbot+9cd5837a045bbee5b810@syzkaller.appspotmail.com > > netlink: 228 bytes leftover after parsing attributes in process > `syz-executor669'. > ================================================================================
The first thing that comes in mind is to check up->dirmask value
#syz test git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
With regards, Pavel Skripkin
From 30db223b1f724ca241c7fa15769d0c65eada3b66 Mon Sep 17 00:00:00 2001 From: Pavel Skripkin <paskripkin@gmail.com> Date: Tue, 27 Jul 2021 17:38:24 +0300 Subject: [PATCH] net: xfrm: fix shift-out-of-bounce
We need to check up->dirmask to avoid shift-out-of-bounce bug, since up->dirmask comes from userspace.
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- net/xfrm/xfrm_user.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index acc3a0dab331..5f3fe2295519 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1966,9 +1966,14 @@ static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh, { struct net *net = sock_net(skb->sk); struct xfrm_userpolicy_default *up = nlmsg_data(nlh); - u8 dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK; + u8 dirmask; u8 old_default = net->xfrm.policy_default; + if (up->dirmask >= sizeof(up->action) * 8) + return -EINVAL; + + dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK + net->xfrm.policy_default = (old_default & (0xff ^ dirmask)) | (up->action << up->dirmask); -- 2.32.0
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