From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794745667; b=1qdaJH2GCmLx9KeaCgtSUKvJqb3m2Q0k9/UlTQuY0InCbkGjMxm9cfgk0DerYR+ymgHu KBqzMzy3bYVkiCQB/x6C8m6QbWrjQNzUT6H3WevGvRaoaF++zTGf3FEnNTXd8ERb2uZ0I 1LtIkEkx1zggSKXwtN6H6l6PH4RTzshXLXMVjn/33ystj23mDxE9epAVCahZ7Ye+jZH6j SAejl4grVpGQz/jtUlu8yGFEud0vehnPKLojzKNFLfHP5vGPQGUG1+quF5VMe2M9EpNsW /kIxvZXAhzDaIvtyYi4KOuCyCNyj7Rtur6HlYIkCo98SPPdWwgnqQ0RNPNrOwdIPZXQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794745667; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition: Content-Transfer-Encoding:In-Reply-To; bh=UAPUreepg71t27uA19huNdBMN8SZC5pl+gBBNOjrEpE=; b=NcAVzKADAVwk8+STifjgUT30gvpQWYznkMKnDW5tMwTmbgjVVUM/oM9i9Sa7LRfHlEzb gaEVuUPYjQP3AmLeGwrsdtmT3f6sKskODMbfjg0xCFQSx2shpsDDnIpknL7D4fxUHuTYC t1R7OmQtCiWyuB8kAyzovv6BVUXdohQ/PrQEGiRb0Unv1YUKtnTXxSpc+v+aYKW3VKvMN AgYkxW7qUBAaiYnuPfUdNNCxIokwWkUjue/SaM8vWK1BAycorOdHY0akQ628rEoKe+X2Y uZPlkMyAyEPJMyEhsiMWnEY4CivzsK8grKd+/+SBN+6sEzB59XlGBdYlEDyJba0E9Tg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lg2tJ8Zf; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32CFF606A31E; Sun, 15 Nov 2026 12:27:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lg2tJ8Zf Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97E8E1F000C4; Sun, 15 Nov 2026 12:27:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794745666; bh=UAPUreepg71t27uA19huNdBMN8SZC5pl+gBBNOjrEpE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=lg2tJ8ZfrKmdiIKH0xpR57qGsXXfv2F5ghS97GTxNPBYY8aqMOGx2U30AnaIf0OtU BwGhDNlCMBUsrfabSbufGfLT3OaR1RYjS9nwKVDAWL8J6AdVpnXLSgwdCGgl2bKeHP VgjCDvrJZoBkLyNSrBbJDQlRKdaGGexyelqo55KgE7EzB9xk4jwa8rwl79TQccZyvz RmmlZGwya6TYgMfbALzKyzOkSeGtq+99zbwJcdGmtM/laJI+bxnQD+irqZdTHdrtQ3 0/6lM2cuN6kAuj4g3ho77thhIa6vswDZPy9tONnIb9v3gpmpvoP3zqyMcal8rxA3qM R3BmAszLUtkkg== Date: Sun, 15 Nov 2026 12:27:42 +0000 From: "Lorenzo Stoakes (ARM)" To: Ivan Ezequiel Rodriguez Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm: use PFN_PHYS() in phys_mem_access_prot() Message-ID: References: <20261113193812.1239880-1-ivanrwcm25@gmail.com> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261113193812.1239880-1-ivanrwcm25@gmail.com> On Fri, Nov 13, 2026 at 04:38:12PM -0300, Ivan Ezequiel Rodriguez wrote: > From: Iván Ezequiel Rodriguez > > phys_mem_access_prot() stores "pfn << PAGE_SHIFT" in a phys_addr_t. > The shift is evaluated as unsigned long, so on a 32-bit kernel with > CONFIG_PHYS_ADDR_T_64BIT an address above 4 GiB is truncated before > uncached_access() compares it with __pa(high_memory). > > mmap_mem_prepare() already shifts in phys_addr_t, so the mapping is > accepted and then left cacheable. PFN_PHYS() casts before the shift. > > On a MIPS32 XPA Malta guest, mmap of /dev/mem at 0xf00000000 without > O_DSYNC used the boot CCA. The same mapping with O_DSYNC was uncached. > With PFN_PHYS() both are uncached. > > Fixes: 7e6735c3578e ("/dev/mem: use phys_addr_t for physical addresses") > Cc: stable@vger.kernel.org > Signed-off-by: Iván Ezequiel Rodriguez LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > mm/char-mem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/char-mem.c b/mm/char-mem.c > index c5761ddedbd7..53ce0034a4c1 100644 > --- a/mm/char-mem.c > +++ b/mm/char-mem.c > @@ -272,7 +272,7 @@ static pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, > unsigned long size, pgprot_t vma_prot) > { > #ifdef pgprot_noncached > - phys_addr_t offset = pfn << PAGE_SHIFT; > + phys_addr_t offset = PFN_PHYS(pfn); > > if (uncached_access(file, offset)) > return pgprot_noncached(vma_prot); > -- > 2.43.0 > -- Cheers, Lorenzo