From d43ad02ad3a88c7ad48969f8458cb0559ac4e75a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Krzysztof=20Wilczy=C5=84ski?= Date: Thu, 29 Jul 2021 23:37:54 +0000 Subject: [PATCH] PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Bjorn Helgaas Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/pci/syscall.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c index 8b003c890b87..c9f03418e71e 100644 --- a/drivers/pci/syscall.c +++ b/drivers/pci/syscall.c @@ -22,8 +22,10 @@ SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn, 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);