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Date:   Fri, 6 Oct 2023 14:39:21 +0200
From:   Mateusz Guzik <mjguzik@gmail.com>
To:     Sven Schnelle <svens@linux.ibm.com>
Cc:     Mark Brown <broonie@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Jann Horn <jannh@google.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org
Subject: Re: Test failure from "file: convert to SLAB_TYPESAFE_BY_RCU"
Message-ID: <ZR//+QDRI3sBpqY4@f>
References: <00e5cc23-a888-46ce-8789-fc182a2131b0@sirena.org.uk>
 <yt9dil7k151d.fsf@linux.ibm.com>
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On Fri, Oct 06, 2023 at 11:19:58AM +0200, Sven Schnelle wrote:
> I'm seeing the same with the strace test-suite on s390. The problem is
> that /proc/*/fd now contains the file descriptors of the calling
> process, and not the target process.
> 

This is why:

+static inline struct file *files_lookup_fdget_rcu(struct files_struct *files, unsigned int fd)
+{
+       RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
+                        "suspicious rcu_dereference_check() usage");
+       return lookup_fdget_rcu(fd);
+}

files argument is now thrown away, instead it always uses current.