linux-kernel - Locking rules for fscrypt_operations->set

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Message-ID: <b6073ec6-3826-a4a1-b1ce-48106c012d43@nod.at>
Date:   Tue, 20 Sep 2016 16:30:06 +0200
From:   Richard Weinberger <richard@....at>
To:     linux-ext4@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Theodore Ts'o <tytso@....edu>, David Gstir <david@...ma-star.at>
Subject: Locking rules for fscrypt_operations->set_context()

Hi!

To my understanding ->setxattr() is always being called with i_mutex held.
->set_context() in ext4 stores the security context using ext4_xattr_set(),
but the fs crypto framework does not lock the inode itself.
So, depending on the call path, ext4_xattr_set() is sometimes being
called with i_mutex held and some times not.

What are the locking rules for fscrypt_operations and especially ->set_context()?

Thanks,
//richard