From 3359e044d597dd5344f17613e4be6b6e12067f60 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= Date: Wed, 29 Jul 2026 07:54:13 +0000 Subject: [PATCH] PCI/proc: Warn on writes to kernel-exclusive config space regions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Currently, a driver can claim a region of a device's config space as exclusive using pci_request_config_region_exclusive(), after which a write to that region originating from user space is expected to emit a warning and taint the kernel. The check is advisory only, as the write itself is still allowed to proceed. Since commit 278294798ac9 ("PCI: Allow drivers to request exclusive config regions"), the sysfs config space attribute performs this check in pci_write_config(), but the procfs interface was never updated. A write performed through /proc/bus/pci/BB/DD.F therefore bypasses the detection entirely, even though both interfaces offer the same level of access. Add the same resource_is_exclusive() check to proc_bus_pci_write(). Signed-off-by: Krzysztof Wilczyński Signed-off-by: Bjorn Helgaas Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260729075413.1215821-1-kwilczynski@kernel.org --- drivers/pci/proc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c index fcbd75d53ac5..5ace1afe498f 100644 --- a/drivers/pci/proc.c +++ b/drivers/pci/proc.c @@ -14,6 +14,8 @@ #include #include #include +#include +#include #include #include "pci.h" @@ -128,6 +130,12 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf, if (!nbytes) return 0; + if (resource_is_exclusive(&dev->driver_exclusive_resource, pos, nbytes)) { + pci_warn_once(dev, "%s: Unexpected write to kernel-exclusive config offset %x", + current->comm, pos); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + } + if (pos >= size) return 0; if (nbytes >= size)