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Message-ID: <1797620e544e77cad9a8cc86d9145e1046d84e6b.camel@redhat.com>
Subject: Re: [PATCH v6 1/4] lib/pci_iomap.c: fix cleanup bug in pci_iounmap()
From: Philipp Stanner <pstanner@redhat.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>, Arnd Bergmann <arnd@arndb.de>, 
 Johannes Berg <johannes@sipsolutions.net>, Randy Dunlap
 <rdunlap@infradead.org>, NeilBrown <neilb@suse.de>,  John Sanpe
 <sanpeqf@gmail.com>, Kent Overstreet <kent.overstreet@gmail.com>, Niklas
 Schnelle <schnelle@linux.ibm.com>, Dave Jiang <dave.jiang@intel.com>,
 Uladzislau Koshchanka <koshchanka@gmail.com>, "Masami Hiramatsu (Google)"
 <mhiramat@kernel.org>, David Gow <davidgow@google.com>, Kees Cook
 <keescook@chromium.org>, Rae Moar <rmoar@google.com>, Geert Uytterhoeven
 <geert@linux-m68k.org>, "wuqiang.matt" <wuqiang.matt@bytedance.com>, Yury
 Norov <yury.norov@gmail.com>, Jason Baron <jbaron@akamai.com>, Thomas
 Gleixner <tglx@linutronix.de>, Marco Elver <elver@google.com>, Andrew
 Morton <akpm@linux-foundation.org>, Ben Dooks <ben.dooks@codethink.co.uk>,
 dakr@redhat.com, linux-kernel@vger.kernel.org,  linux-pci@vger.kernel.org,
 linux-arch@vger.kernel.org, stable@vger.kernel.org,  Arnd Bergmann
 <arnd@kernel.org>
Date: Tue, 06 Feb 2024 10:36:42 +0100
In-Reply-To: <20240131210944.GA599710@bhelgaas>
References: <20240131210944.GA599710@bhelgaas>
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On Wed, 2024-01-31 at 15:09 -0600, Bjorn Helgaas wrote:
> On Wed, Jan 31, 2024 at 10:00:20AM +0100, Philipp Stanner wrote:
> > The #ifdef for the ioport-ranges accidentally also guards
> > iounmap(),
> > potentially compiling an empty function. This would cause the
> > mapping to
> > be leaked.
> >=20
> > Move the guard so that iounmap() will always be part of the
> > function.
>=20
> I tweaked the subject and commit log to be more explicit about what
> the bug is.=C2=A0 Let me know if I got it wrong:

Mostly correct IMO

>=20
> =C2=A0 pci_iounmap(): Fix MMIO mapping leak
>=20
> =C2=A0 The #ifdef ARCH_HAS_GENERIC_IOPORT_MAP accidentally also guards
> iounmap(),
> =C2=A0 which means MMIO mappings are leaked.

nit: I wasn't entirely sure when they are actually leaked, just that
they _could_ be leaked. To know for sure we'd need to search who sets
ARCH_WANTS_GENERIC_PCI_IOUNMAP without setting
ARCH_HAS_GENERIC_IOPORT_MAP.

I think your formulation should be fine, though, since it's definitely
a bug.

P.

>=20
> =C2=A0 Move the guard so we call iounmap() for MMIO mappings.
>=20
> Bjorn
>=20