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d43ad02ad3
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 aftere4585da22a("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 aftere4585da22a, 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:e4585da22a("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@linux.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
139 lines
2.7 KiB
C
139 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* For architectures where we want to allow direct access to the PCI config
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* stuff - it would probably be preferable on PCs too, but there people
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* just do it by hand with the magic northbridge registers.
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*/
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#include <linux/errno.h>
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#include <linux/pci.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/uaccess.h>
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#include "pci.h"
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SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn,
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unsigned long, off, unsigned long, len, void __user *, buf)
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{
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struct pci_dev *dev;
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u8 byte;
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u16 word;
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u32 dword;
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long err;
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int cfg_ret;
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err = -EPERM;
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dev = NULL;
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if (!capable(CAP_SYS_ADMIN))
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goto error;
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err = -ENODEV;
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dev = pci_get_domain_bus_and_slot(0, bus, dfn);
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if (!dev)
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goto error;
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switch (len) {
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case 1:
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cfg_ret = pci_user_read_config_byte(dev, off, &byte);
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break;
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case 2:
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cfg_ret = pci_user_read_config_word(dev, off, &word);
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break;
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case 4:
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cfg_ret = pci_user_read_config_dword(dev, off, &dword);
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break;
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default:
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err = -EINVAL;
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goto error;
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}
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err = -EIO;
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if (cfg_ret)
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goto error;
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switch (len) {
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case 1:
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err = put_user(byte, (unsigned char __user *)buf);
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break;
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case 2:
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err = put_user(word, (unsigned short __user *)buf);
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break;
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case 4:
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err = put_user(dword, (unsigned int __user *)buf);
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break;
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}
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pci_dev_put(dev);
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return err;
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error:
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/* ??? XFree86 doesn't even check the return value. They
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just look for 0xffffffff in the output, since that's what
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they get instead of a machine check on x86. */
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switch (len) {
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case 1:
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put_user(-1, (unsigned char __user *)buf);
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break;
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case 2:
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put_user(-1, (unsigned short __user *)buf);
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break;
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case 4:
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put_user(-1, (unsigned int __user *)buf);
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break;
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}
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pci_dev_put(dev);
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return err;
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}
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SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
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unsigned long, off, unsigned long, len, void __user *, buf)
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{
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struct pci_dev *dev;
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u8 byte;
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u16 word;
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u32 dword;
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int err = 0;
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if (!capable(CAP_SYS_ADMIN) ||
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security_locked_down(LOCKDOWN_PCI_ACCESS))
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return -EPERM;
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dev = pci_get_domain_bus_and_slot(0, bus, dfn);
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if (!dev)
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return -ENODEV;
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switch (len) {
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case 1:
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err = get_user(byte, (u8 __user *)buf);
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if (err)
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break;
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err = pci_user_write_config_byte(dev, off, byte);
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if (err)
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err = -EIO;
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break;
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case 2:
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err = get_user(word, (u16 __user *)buf);
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if (err)
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break;
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err = pci_user_write_config_word(dev, off, word);
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if (err)
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err = -EIO;
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break;
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case 4:
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err = get_user(dword, (u32 __user *)buf);
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if (err)
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break;
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err = pci_user_write_config_dword(dev, off, dword);
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if (err)
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err = -EIO;
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break;
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default:
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err = -EINVAL;
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break;
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}
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pci_dev_put(dev);
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return err;
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}
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