From: Krzysztof Wilczyński Date: Thu, 29 Jul 2021 23:37:54 +0000 (+0000) Subject: PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure X-Git-Tag: v5.13.19~318 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0f3c6b3c49cdb4df8d6a10a9283a61235bad5a39;p=thirdparty%2Fkernel%2Fstable.git PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure 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 --- diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c index 8b003c890b87b..c9f03418e71e0 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);