linux-kernel - Re: Test failure from "file: convert to SLAB_TYPESAFE_BY

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Message-ID: <ZR//+QDRI3sBpqY4@f>
Date:   Fri, 6 Oct 2023 14:39:21 +0200
From:   Mateusz Guzik <mjguzik@...il.com>
To:     Sven Schnelle <svens@...ux.ibm.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Jann Horn <jannh@...gle.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: Test failure from "file: convert to SLAB_TYPESAFE_BY_RCU"

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.