linux-kernel - [PATCH 5.14 066/432] PCI: Return ~0 data on pciconfig_read() CAP_SYS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210916155813.023542107@linuxfoundation.org>
Date:   Thu, 16 Sep 2021 17:56:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH 5.14 066/432] PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure

From: Krzysztof Wilczyński <kw@...ux.com>

commit a8bd29bd49c4156ea0ec5a97812333e2aeef44e7 upstream.

The pciconfig_read() syscall reads PCI configuration space using
hardware-dependent config accessors.

If the read fails on PCI, most accessors don't return an error; they
pretend the read was successful and got ~0 data from the device, so the
syscall returns success with ~0 data in the buffer.

When the accessor does return an error, pciconfig_read() normally fills the
user's buffer with ~0 and returns an error in errno.  But after
e4585da22ad0 ("pci syscall.c: Switch to refcounting API"), we don't fill
the buffer with ~0 for the EPERM "user lacks CAP_SYS_ADMIN" error.

Userspace may rely on the ~0 data to detect errors, but after e4585da22ad0,
that would not detect CAP_SYS_ADMIN errors.

Restore the original behaviour of filling the buffer with ~0 when the
CAP_SYS_ADMIN check fails.

[bhelgaas: commit log, fold in Nathan's fix
https://lore.kernel.org/r/20210803200836.500658-1-nathan@kernel.org]
Fixes: e4585da22ad0 ("pci syscall.c: Switch to refcounting API")
Link: https://lore.kernel.org/r/20210729233755.1509616-1-kw@linux.com
Signed-off-by: Krzysztof Wilczyński <kw@...ux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/pci/syscall.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -22,8 +22,10 @@ SYSCALL_DEFINE5(pciconfig_read, unsigned
 	long err;
 	int cfg_ret;

+	err = -EPERM;
+	dev = NULL;
 	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
+		goto error;

 	err = -ENODEV;
 	dev = pci_get_domain_bus_and_slot(0, bus, dfn);