From: "Chuck Lever" <cel@kernel.org>
To: "Alessandro Zanni" <alessandro.zanni87@gmail.com>,
"Chuck Lever" <chuck.lever@oracle.com>,
"Jeff Layton" <jlayton@kernel.org>, NeilBrown <neil@brown.name>,
"Olga Kornievskaia" <okorniev@redhat.com>,
"Dai Ngo" <Dai.Ngo@oracle.com>, "Tom Talpey" <tom@talpey.com>,
"Trond Myklebust" <trondmy@kernel.org>,
"Anna Schumaker" <anna@kernel.org>,
davem@davemloft.net, edumazet@google.com,
"Jakub Kicinski" <kuba@kernel.org>,
"Paolo Abeni" <pabeni@redhat.com>,
"Simon Horman" <horms@kernel.org>
Cc: linux-nfs@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
syzbot+60cfa08822470bbebe44@syzkaller.appspotmail.com
Subject: Re: [PATCH] net: sunrpc: fix slab-out-of-bounds read in cache_seq_start_rcu
Date: Tue, 28 Apr 2026 09:56:42 -0400 [thread overview]
Message-ID: <f13ad5ba-1b1e-4bf9-8acb-07b5530e1da5@app.fastmail.com> (raw)
In-Reply-To: <20260428134230.136533-1-alessandro.zanni87@gmail.com>
On Tue, Apr 28, 2026, at 9:42 AM, Alessandro Zanni wrote:
> Syzbot reported slab-out-of-bounds read in cache_seq_start_rcu().
>
> The issue happens in function __cache_seq_start() when is invoked
> hlist_for_each_entry_rcu() and the hash value is greater than the
> hash_size.
>
> This fix verifies that the hash index is within the hash_size value
> before dereferencing the hash table: if the hash index is out of
> bounds return NULL, otherwise access the value.
>
> Fixes: ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection
> rather than the r/w spinlock")
> Reported-by: syzbot+60cfa08822470bbebe44@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=60cfa08822470bbebe44
> Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
> ---
> net/sunrpc/cache.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
> index 7081c1214e6c..aac5f03112f5 100644
> --- a/net/sunrpc/cache.c
> +++ b/net/sunrpc/cache.c
> @@ -1348,6 +1348,9 @@ static void *__cache_seq_start(struct seq_file
> *m, loff_t *pos)
> hash = n >> 32;
> entry = n & ((1LL<<32) - 1);
>
> + if (hash >= cd->hash_size)
> + return NULL;
> +
> hlist_for_each_entry_rcu(ch, &cd->hash_table[hash], cache_list)
> if (!entry--)
> return ch;
> --
> 2.47.3
Thank you for the patch! We have this fixed in the nfsd-testing
tree already:
https://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git/commit/?h=nfsd-testing&id=72fe9e528c68aa7b9ed5afab98c44f8b83bbe287
--
Chuck Lever
prev parent reply other threads:[~2026-04-28 13:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-28 13:42 [PATCH] net: sunrpc: fix slab-out-of-bounds read in cache_seq_start_rcu Alessandro Zanni
2026-04-28 13:56 ` Chuck Lever [this message]
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