netdev - Re: [PATCH net v4 2/3] Treewide: Stop corrupting socket's task

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Date:   Tue, 3 Jan 2023 15:26:27 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Benjamin Coddington <bcodding@...hat.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Guillaume Nault <gnault@...hat.com>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Lars Ellenberg <lars.ellenberg@...bit.com>,
        Christoph Böhmwalder 
        <christoph.boehmwalder@...bit.com>, Jens Axboe <axboe@...nel.dk>,
        Josef Bacik <josef@...icpanda.com>,
        Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Lee Duncan <lduncan@...e.com>, Chris Leech <cleech@...hat.com>,
        Mike Christie <michael.christie@...cle.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Howells <dhowells@...hat.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        Steve French <sfrench@...ba.org>,
        Christine Caulfield <ccaulfie@...hat.com>,
        David Teigland <teigland@...hat.com>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Latchesar Ionkov <lucho@...kov.net>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Xiubo Li <xiubli@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net v4 2/3] Treewide: Stop corrupting socket's task_frag

On Fri, Dec 16, 2022 at 1:45 PM Benjamin Coddington <bcodding@...hat.com> wrote:
>
> Since moving to memalloc_nofs_save/restore, SUNRPC has stopped setting the
> GFP_NOIO flag on sk_allocation which the networking system uses to decide
> when it is safe to use current->task_frag.  The results of this are
> unexpected corruption in task_frag when SUNRPC is involved in memory
> reclaim.
>
> The corruption can be seen in crashes, but the root cause is often
> difficult to ascertain as a crashing machine's stack trace will have no
> evidence of being near NFS or SUNRPC code.  I believe this problem to
> be much more pervasive than reports to the community may indicate.
>
> Fix this by having kernel users of sockets that may corrupt task_frag due
> to reclaim set sk_use_task_frag = false.  Preemptively correcting this
> situation for users that still set sk_allocation allows them to convert to
> memalloc_nofs_save/restore without the same unexpected corruptions that are
> sure to follow, unlikely to show up in testing, and difficult to bisect.
>

I am back from PTO.

It seems inet_ctl_sock_create() has been forgotten.

Without following fix, ICMP messages sent from softirq would corrupt
innocent thread task_frag.

(I will submit this patch formally a bit later today)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index ab4a06be489b5d410cec603bf56248d31dbc90dd..6c0ec27899431eb56e2f9d0c3a936b77f44ccaca
100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1665,6 +1665,7 @@ int inet_ctl_sock_create(struct sock **sk,
unsigned short family,
        if (rc == 0) {
                *sk = sock->sk;
                (*sk)->sk_allocation = GFP_ATOMIC;
+               (*sk)->sk_use_task_frag = false;
                /*
                 * Unhash it so that IP input processing does not even see it,
                 * we do not wish this socket to see incoming packets.