From: Thomas Gleixner <tglx@linutronix.de>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Darren Hart <dvhart@infradead.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Andre Almeida <andrealmeid@igalia.com>,
Andrew Morton <akpm@linux-foundation.org>,
Eric Dumazet <edumazet@google.com>,
Kuniyuki Iwashima <kuniyu@google.com>,
Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemb@google.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Simon Horman <horms@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Dave Hansen <dave.hansen@linux.intel.com>,
Madhavan Srinivasan <maddy@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 02/10] uaccess: Add speculation barrier to copy_from_user_iter()
Date: Sat, 15 Nov 2025 16:51:59 +0100 [thread overview]
Message-ID: <87jyzr9tuo.ffs@tglx> (raw)
In-Reply-To: <598e9ec31716ce351f1456c81eee140477d4ecc4.1762427933.git.christophe.leroy@csgroup.eu>
On Thu, Nov 06 2025 at 12:31, Christophe Leroy wrote:
> The results of "access_ok()" can be mis-speculated. The result is that
> you can end speculatively:
>
> if (access_ok(from, size))
> // Right here
This is actually the wrong patch ordering as the barrier is missing in
the current code. So please add the missing barrier first.
As a bonus the subject of the first patch makes actually sense
then. Right now it does not because there is nothing to avoid :)
Also please use the same prefix for these two patches which touch the
iter code.
> For the same reason as done in copy_from_user() by
> commit 74e19ef0ff80 ("uaccess: Add speculation barrier to
> copy_from_user()"), add a speculation barrier to copy_from_user_iter().
>
> See commit 74e19ef0ff80 ("uaccess: Add speculation barrier to
> copy_from_user()") for more details.
No need to repeat that. Anyone with more than two braincells can look at
that commit, which you mentioned already two lines above already.
Thanks,
tglx
next prev parent reply other threads:[~2025-11-15 15:52 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-06 11:31 [PATCH v4 00/10] powerpc: Implement masked user access Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 01/10] iter: Avoid barrier_nospec() in copy_from_user_iter() Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 02/10] uaccess: Add speculation barrier to copy_from_user_iter() Christophe Leroy
2025-11-15 15:51 ` Thomas Gleixner [this message]
2025-11-17 7:06 ` Christophe Leroy (CS GROUP)
2025-11-06 11:31 ` [PATCH v4 03/10] uaccess: Use masked_user_{read/write}_access_begin when required Christophe Leroy
2025-11-15 15:53 ` Thomas Gleixner
2025-11-17 7:11 ` Christophe Leroy (CS GROUP)
2025-11-06 11:31 ` [PATCH v4 04/10] powerpc/uaccess: Move barrier_nospec() out of allow_read_{from/write}_user() Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 05/10] powerpc/uaccess: Remove unused size and from parameters from allow_access_user() Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 06/10] powerpc/uaccess: Remove {allow/prevent}_{read/write/read_write}_{from/to/}_user() Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 07/10] powerpc/uaccess: Refactor user_{read/write/}_access_begin() Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 08/10] powerpc/32s: Fix segments setup when TASK_SIZE is not a multiple of 256M Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 09/10] powerpc/32: Automatically adapt TASK_SIZE based on constraints Christophe Leroy
2025-11-06 11:31 ` [PATCH v4 10/10] powerpc/uaccess: Implement masked user access Christophe Leroy
2025-11-06 12:35 ` Peter Zijlstra
2025-11-06 13:42 ` David Laight
2025-11-13 6:10 ` [PATCH v4 00/10] powerpc: " Madhavan Srinivasan
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