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From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Redundant barrier_nospec() added by commit 74e19ef0ff80 ("uaccess: Add speculation barrier to copy_from_user()")
Date: Thu, 19 Jun 2025 10:42:13 +0200	[thread overview]
Message-ID: <6f58923f-5ee2-41c6-bb73-8e0fb9ad9a96@csgroup.eu> (raw)

Hello Dave,

In commit 74e19ef0ff80 ("uaccess: Add speculation barrier to 
copy_from_user()") you add barrier_nospec() to copy_from_user().

There is already a barrier_nospec() in allow_read_from_user() which is 
called by raw_copy_from_user(), see commit 8524e2e76441 
("powerpc/uaccess: Perform barrier_nospec() in KUAP allowance helpers"). 
Why do you need an additional one ?

And why only copy_from_user() and not also other places like 
copy_from_user_iter() for instance ?

Thanks
Christophe



                 reply	other threads:[~2025-06-19  8:42 UTC|newest]

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