linux-kernel - Re: [PATCH net] crypto: af_alg: Fix merging of written data into spliced pages

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Message-ID: <CAAUqJDv26FBuG+UYDc+xBYz0b8V-+eDzzLXjianmWAAo_JwvLg@mail.gmail.com>
Date:   Tue, 11 Jul 2023 10:31:27 +0200
From:   Ondrej Mosnáček <omosnacek@...il.com>
To:     David Howells <dhowells@...hat.com>
Cc:     netdev@...r.kernel.org, Herbert Xu <herbert@...dor.apana.org.au>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] crypto: af_alg: Fix merging of written data into
 spliced pages

On Tue, Jul 4, 2023 at 5:56 PM David Howells <dhowells@...hat.com> wrote:
> af_alg_sendmsg() takes data-to-be-copied that's provided by write(),
> send(), sendmsg() and similar into pages that it allocates and will merge
> new data into the last page in the list, based on the value of ctx->merge.
>
> Now that af_alg_sendmsg() accepts MSG_SPLICE_PAGES, it adds spliced pages
> directly into the list and then incorrectly appends data to them if there's
> space left because ctx->merge says that it can.  This was cleared by
> af_alg_sendpage(), but that got lost.
>
> Fix this by skipping the merge if MSG_SPLICE_PAGES is specified and
> clearing ctx->merge after MSG_SPLICE_PAGES has added stuff to the list.
>
> Fixes: bf63e250c4b1 ("crypto: af_alg: Support MSG_SPLICE_PAGES")
> Reported-by: Ondrej Mosnáček <omosnacek@...il.com>
> Link: https://lore.kernel.org/r/CAAUqJDvFuvms55Td1c=XKv6epfRnnP78438nZQ-JKyuCptGBiQ@mail.gmail.com/
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Herbert Xu <herbert@...dor.apana.org.au>
> cc: Paolo Abeni <pabeni@...hat.com>
> cc: "David S. Miller" <davem@...emloft.net>
> cc: Eric Dumazet <edumazet@...gle.com>
> cc: Jakub Kicinski <kuba@...nel.org>
> cc: linux-crypto@...r.kernel.org
> cc: netdev@...r.kernel.org
> ---
>  crypto/af_alg.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Thanks for the fix! I can confirm that it fixes the reported issue.
There remains some kernel panic on s390x that I hadn't noticed in the
results earlier, but that's probably a different issue. I'll
investigate and send a report/patch when I have more information.