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Fri, 7 Mar 2025 04:33:14 -0800 (PST) From: Ryan Roberts To: Andrew Morton , Lorenzo Stoakes Cc: Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v1] mm/madvise: Always set ptes via arch helpers Date: Fri, 7 Mar 2025 12:33:06 +0000 Message-ID: <20250307123307.262298-1-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-Stat-Signature: hypj6kw65frrxjrdkyk6nd8p7jundnie X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0CE1B80007 X-Rspam-User: X-HE-Tag: 1741350795-997367 X-HE-Meta: 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 jszVSM1i iITnlAiqnsqmufDad60OmfVWzvFxzADAIQrmT2hJERcOyDkbyi1z8xRzs0rdy90PZrTY4EsN+2JLezUDHn0NO2On/+hbMmHdj0arux+AfqFfl60LazEfN10S//AhJZTILWSLTXagnH5oR4+LB49hQeoxubM0jLCkP0Fj6OF7HLIA65qU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Instead of writing a pte directly into the table, use the set_pte_at() helper, which gives the arch visibility of the change. In this instance we are guaranteed that the pte was originally none and is being modified to a not-present pte, so there was unlikely to be a bug in practice (at least not on arm64). But it's bad practice to write the page table memory directly without arch involvement. Cc: Fixes: 662df3e5c376 ("mm: madvise: implement lightweight guard page mechanism") Signed-off-by: Ryan Roberts --- mm/madvise.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.43.0 diff --git a/mm/madvise.c b/mm/madvise.c index 388dc289b5d1..6170f4acc14f 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1101,7 +1101,7 @@ static int guard_install_set_pte(unsigned long addr, unsigned long next, unsigned long *nr_pages = (unsigned long *)walk->private; /* Simply install a PTE marker, this causes segfault on access. */ - *ptep = make_pte_marker(PTE_MARKER_GUARD); + set_pte_at(walk->mm, addr, ptep, make_pte_marker(PTE_MARKER_GUARD)); (*nr_pages)++; return 0;