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From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: Bart Van Assche <bvanassche@acm.org>,
	Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christophe Leroy <chleroy@kernel.org>,
	Shrikanth Hegde <sshegde@linux.ibm.com>, Qian Cai <cai@lca.pw>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH] powerpc/iommu: Fix an RCU read lock leak in mm_iommu_is_devmem()
Date: Tue, 27 Oct 2026 06:43:59 +0530	[thread overview]
Message-ID: <bj8g54iw.ritesh.list@gmail.com> (raw)
In-Reply-To: <56f0c45723ee53149a21ceb599010e957457afd8.1793044370.git.bvanassche@acm.org>

Bart Van Assche <bvanassche@acm.org> writes:

> mm_iommu_is_devmem() returns true from inside its RCU read-side
> critical section without calling rcu_read_unlock(). Neither caller,
> iommu_tce_xchg_no_kill() nor tce_page_is_contained(), drops the RCU
> read lock, so every successful lookup leaks one RCU read lock. Fix this
> by calling rcu_read_unlock() before returning true. The pointer to the
> list element is not used after the RCU read lock is dropped.
>
> Fixes: b5952f8125ae ("powerpc/mm/book3s64/iommu: fix some RCU-list locks")

Thanks Bart, but this was caught as part of Clang's context analysis
work on powerpc.  It is already posted here [1]. Could you review that
instead?

[1]: https://lore.kernel.org/linuxppc-dev/04e4dafde56fe4b055fbd763dc0e119862073c6d.1790590014.git.ritesh.list@gmail.com/

-ritesh

      parent reply	other threads:[~2026-10-27  1:17 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-26 19:52 Bart Van Assche
2026-10-26 20:27 ` Markus Elfring
2026-10-26 20:33   ` Bart Van Assche
2026-10-27  1:13 ` Ritesh Harjani [this message]

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