[PATCH 1/2] ethtool: improve compat ioctl handling

From: Arnd Bergmann
Date: Fri Sep 18 2020 - 08:06:30 EST

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The ethtool compat ioctl handling is hidden away in net/socket.c,
which introduces a couple of minor oddities:

- The implementation may end up diverging, as seen in the RXNFC
extension in commit 84a1d9c48200 ("net: ethtool: extend RXNFC
API to support RSS spreading of filter matches") that does not work
in compat mode.

- Most architectures do not need the compat handling at all
because u64 and compat_u64 have the same alignment.

- On x86, the conversion is done for both x32 and i386 user space,
but it's actually wrong to do it for x32 and cannot work there.

- On 32-bit Arm, it never worked for compat oabi user space, since
that needs to do the same conversion but does not.

- It would be nice to get rid of both compat_alloc_user_space()
and copy_in_user() throughout the kernel.

None of these actually seems to be a serious problem that real
users are likely to encounter, but fixing all of them actually
leads to code that is both shorter and more readable.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
include/linux/ethtool.h | 4 --
net/ethtool/ioctl.c | 129 +++++++++++++++++++++++++++++++++++-----
net/socket.c | 125 +-------------------------------------
3 files changed, 114 insertions(+), 144 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 969a80211df6..283987123022 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -17,8 +17,6 @@
#include <linux/compat.h>
#include <uapi/linux/ethtool.h>

-#ifdef CONFIG_COMPAT
-
struct compat_ethtool_rx_flow_spec {
u32 flow_type;
union ethtool_flow_union h_u;
@@ -38,8 +36,6 @@ struct compat_ethtool_rxnfc {
u32 rule_locs[];
};

-#endif /* CONFIG_COMPAT */
-
#include <linux/rculist.h>

/**
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 441794e0034f..38ae16f095a5 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -7,6 +7,7 @@
* the information ethtool needs.
*/

+#include <linux/compat.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/capability.h>
@@ -807,6 +808,113 @@ static noinline_for_stack int ethtool_get_sset_info(struct net_device *dev,
return ret;
}

+static inline bool ethtool_translate_compat(void)
+{
+#ifdef CONFIG_X86_64
+ /* On x86, translation is needed for i386 but not x32 */
+ return in_ia32_syscall();
+#elif defined(CONFIG_ARM)
+ /* On 32-bit Arm, translation is needed for OABI only */
+ return in_oabi_syscall();
+#else
+ BUILD_BUG_ON(sizeof(struct compat_ethtool_rxnfc) !=
+ sizeof(struct ethtool_rxnfc));
+#endif
+
+ return 0;
+}
+
+static int ethtool_rxnfc_copy_from_user(struct ethtool_rxnfc *rxnfc,
+ const struct compat_ethtool_rxnfc __user *useraddr,
+ size_t size)
+{
+ /* We expect there to be holes between fs.m_ext and
+ * fs.ring_cookie and at the end of fs, but nowhere else.
+ */
+ BUILD_BUG_ON(offsetof(struct compat_ethtool_rxnfc, fs.m_ext) +
+ sizeof(useraddr->fs.m_ext) !=
+ offsetof(struct ethtool_rxnfc, fs.m_ext) +
+ sizeof(rxnfc->fs.m_ext));
+ BUILD_BUG_ON(offsetof(struct compat_ethtool_rxnfc, fs.location) -
+ offsetof(struct compat_ethtool_rxnfc, fs.ring_cookie) !=
+ offsetof(struct ethtool_rxnfc, fs.location) -
+ offsetof(struct ethtool_rxnfc, fs.ring_cookie));
+
+ if (ethtool_translate_compat()) {
+ struct compat_ethtool_rxnfc crxnfc = {};
+
+ if (copy_from_user(&crxnfc, useraddr,
+ min(size, sizeof(crxnfc))))
+ return -EFAULT;
+
+ *rxnfc = (struct ethtool_rxnfc) {
+ .cmd = crxnfc.cmd,
+ .flow_type = crxnfc.flow_type,
+ .data = crxnfc.data,
+ .fs = {
+ .flow_type = crxnfc.fs.flow_type,
+ .h_u = crxnfc.fs.h_u,
+ .h_ext = crxnfc.fs.h_ext,
+ .m_u = crxnfc.fs.m_u,
+ .m_ext = crxnfc.fs.m_ext,
+ .ring_cookie = crxnfc.fs.ring_cookie,
+ .location = crxnfc.fs.location,
+ },
+ .rule_cnt = crxnfc.rule_cnt,
+ };
+ } else {
+ if (copy_from_user(&rxnfc, useraddr, size))
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+static int ethtool_rxnfc_copy_to_user(void __user *useraddr,
+ const struct ethtool_rxnfc *rxnfc,
+ size_t size, const u32 *rule_buf)
+{
+ int ret;
+
+ if (ethtool_translate_compat()) {
+ struct compat_ethtool_rxnfc crxnfc;
+
+ memset(&crxnfc, 0, sizeof(crxnfc));
+ crxnfc = (struct compat_ethtool_rxnfc) {
+ .cmd = rxnfc->cmd,
+ .flow_type = rxnfc->flow_type,
+ .data = rxnfc->data,
+ .fs = {
+ .flow_type = rxnfc->fs.flow_type,
+ .h_u = rxnfc->fs.h_u,
+ .h_ext = rxnfc->fs.h_ext,
+ .m_u = rxnfc->fs.m_u,
+ .m_ext = rxnfc->fs.m_ext,
+ .ring_cookie = rxnfc->fs.ring_cookie,
+ .location = rxnfc->fs.location,
+ },
+ .rule_cnt = rxnfc->rule_cnt,
+ };
+
+ ret = copy_to_user(useraddr, &crxnfc, min(size, sizeof(crxnfc)));
+ useraddr += offsetof(struct compat_ethtool_rxnfc, rule_locs);
+ } else {
+ ret = copy_to_user(useraddr, &rxnfc, size);
+ useraddr += offsetof(struct ethtool_rxnfc, rule_locs);
+ }
+
+ if (ret)
+ return -EFAULT;
+
+ if (rule_buf) {
+ if (copy_to_user(useraddr, rule_buf,
+ rxnfc->rule_cnt * sizeof(u32)))
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
u32 cmd, void __user *useraddr)
{
@@ -825,7 +933,7 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
info_size = (offsetof(struct ethtool_rxnfc, data) +
sizeof(info.data));

- if (copy_from_user(&info, useraddr, info_size))
+ if (ethtool_rxnfc_copy_from_user(&info, useraddr, info_size))
return -EFAULT;

rc = dev->ethtool_ops->set_rxnfc(dev, &info);
@@ -833,7 +941,7 @@ static noinline_for_stack int ethtool_set_rxnfc(struct net_device *dev,
return rc;

if (cmd == ETHTOOL_SRXCLSRLINS &&
- copy_to_user(useraddr, &info, info_size))
+ ethtool_rxnfc_copy_to_user(useraddr, &info, info_size, NULL))
return -EFAULT;

return 0;
@@ -859,7 +967,7 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
info_size = (offsetof(struct ethtool_rxnfc, data) +
sizeof(info.data));

- if (copy_from_user(&info, useraddr, info_size))
+ if (ethtool_rxnfc_copy_from_user(&info, useraddr, info_size))
return -EFAULT;

/* If FLOW_RSS was requested then user-space must be using the
@@ -867,7 +975,7 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
*/
if (cmd == ETHTOOL_GRXFH && info.flow_type & FLOW_RSS) {
info_size = sizeof(info);
- if (copy_from_user(&info, useraddr, info_size))
+ if (ethtool_rxnfc_copy_from_user(&info, useraddr, info_size))
return -EFAULT;
/* Since malicious users may modify the original data,
* we need to check whether FLOW_RSS is still requested.
@@ -893,18 +1001,7 @@ static noinline_for_stack int ethtool_get_rxnfc(struct net_device *dev,
if (ret < 0)
goto err_out;

- ret = -EFAULT;
- if (copy_to_user(useraddr, &info, info_size))
- goto err_out;
-
- if (rule_buf) {
- useraddr += offsetof(struct ethtool_rxnfc, rule_locs);
- if (copy_to_user(useraddr, rule_buf,
- info.rule_cnt * sizeof(u32)))
- goto err_out;
- }
- ret = 0;
-
+ ret = ethtool_rxnfc_copy_to_user(useraddr, &info, info_size, rule_buf);
err_out:
kfree(rule_buf);

diff --git a/net/socket.c b/net/socket.c
index dbbe8ea7d395..3fe30ba2a09a 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3121,128 +3121,6 @@ static int compat_dev_ifconf(struct net *net, struct compat_ifconf __user *uifc3
return 0;
}

-static int ethtool_ioctl(struct net *net, struct compat_ifreq __user *ifr32)
-{
- struct compat_ethtool_rxnfc __user *compat_rxnfc;
- bool convert_in = false, convert_out = false;
- size_t buf_size = 0;
- struct ethtool_rxnfc __user *rxnfc = NULL;
- struct ifreq ifr;
- u32 rule_cnt = 0, actual_rule_cnt;
- u32 ethcmd;
- u32 data;
- int ret;
-
- if (get_user(data, &ifr32->ifr_ifru.ifru_data))
- return -EFAULT;
-
- compat_rxnfc = compat_ptr(data);
-
- if (get_user(ethcmd, &compat_rxnfc->cmd))
- return -EFAULT;
-
- /* Most ethtool structures are defined without padding.
- * Unfortunately struct ethtool_rxnfc is an exception.
- */
- switch (ethcmd) {
- default:
- break;
- case ETHTOOL_GRXCLSRLALL:
- /* Buffer size is variable */
- if (get_user(rule_cnt, &compat_rxnfc->rule_cnt))
- return -EFAULT;
- if (rule_cnt > KMALLOC_MAX_SIZE / sizeof(u32))
- return -ENOMEM;
- buf_size += rule_cnt * sizeof(u32);
- fallthrough;
- case ETHTOOL_GRXRINGS:
- case ETHTOOL_GRXCLSRLCNT:
- case ETHTOOL_GRXCLSRULE:
- case ETHTOOL_SRXCLSRLINS:
- convert_out = true;
- fallthrough;
- case ETHTOOL_SRXCLSRLDEL:
- buf_size += sizeof(struct ethtool_rxnfc);
- convert_in = true;
- rxnfc = compat_alloc_user_space(buf_size);
- break;
- }
-
- if (copy_from_user(&ifr.ifr_name, &ifr32->ifr_name, IFNAMSIZ))
- return -EFAULT;
-
- ifr.ifr_data = convert_in ? rxnfc : (void __user *)compat_rxnfc;
-
- if (convert_in) {
- /* We expect there to be holes between fs.m_ext and
- * fs.ring_cookie and at the end of fs, but nowhere else.
- */
- BUILD_BUG_ON(offsetof(struct compat_ethtool_rxnfc, fs.m_ext) +
- sizeof(compat_rxnfc->fs.m_ext) !=
- offsetof(struct ethtool_rxnfc, fs.m_ext) +
- sizeof(rxnfc->fs.m_ext));
- BUILD_BUG_ON(
- offsetof(struct compat_ethtool_rxnfc, fs.location) -
- offsetof(struct compat_ethtool_rxnfc, fs.ring_cookie) !=
- offsetof(struct ethtool_rxnfc, fs.location) -
- offsetof(struct ethtool_rxnfc, fs.ring_cookie));
-
- if (copy_in_user(rxnfc, compat_rxnfc,
- (void __user *)(&rxnfc->fs.m_ext + 1) -
- (void __user *)rxnfc) ||
- copy_in_user(&rxnfc->fs.ring_cookie,
- &compat_rxnfc->fs.ring_cookie,
- (void __user *)(&rxnfc->fs.location + 1) -
- (void __user *)&rxnfc->fs.ring_cookie))
- return -EFAULT;
- if (ethcmd == ETHTOOL_GRXCLSRLALL) {
- if (put_user(rule_cnt, &rxnfc->rule_cnt))
- return -EFAULT;
- } else if (copy_in_user(&rxnfc->rule_cnt,
- &compat_rxnfc->rule_cnt,
- sizeof(rxnfc->rule_cnt)))
- return -EFAULT;
- }
-
- ret = dev_ioctl(net, SIOCETHTOOL, &ifr, NULL);
- if (ret)
- return ret;
-
- if (convert_out) {
- if (copy_in_user(compat_rxnfc, rxnfc,
- (const void __user *)(&rxnfc->fs.m_ext + 1) -
- (const void __user *)rxnfc) ||
- copy_in_user(&compat_rxnfc->fs.ring_cookie,
- &rxnfc->fs.ring_cookie,
- (const void __user *)(&rxnfc->fs.location + 1) -
- (const void __user *)&rxnfc->fs.ring_cookie) ||
- copy_in_user(&compat_rxnfc->rule_cnt, &rxnfc->rule_cnt,
- sizeof(rxnfc->rule_cnt)))
- return -EFAULT;
-
- if (ethcmd == ETHTOOL_GRXCLSRLALL) {
- /* As an optimisation, we only copy the actual
- * number of rules that the underlying
- * function returned. Since Mallory might
- * change the rule count in user memory, we
- * check that it is less than the rule count
- * originally given (as the user buffer size),
- * which has been range-checked.
- */
- if (get_user(actual_rule_cnt, &rxnfc->rule_cnt))
- return -EFAULT;
- if (actual_rule_cnt < rule_cnt)
- rule_cnt = actual_rule_cnt;
- if (copy_in_user(&compat_rxnfc->rule_locs[0],
- &rxnfc->rule_locs[0],
- rule_cnt * sizeof(u32)))
- return -EFAULT;
- }
- }
-
- return 0;
-}
-
static int compat_siocwandev(struct net *net, struct compat_ifreq __user *uifr32)
{
compat_uptr_t uptr32;
@@ -3397,8 +3275,6 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
return old_bridge_ioctl(argp);
case SIOCGIFCONF:
return compat_dev_ifconf(net, argp);
- case SIOCETHTOOL:
- return ethtool_ioctl(net, argp);
case SIOCWANDEV:
return compat_siocwandev(net, argp);
case SIOCGIFMAP:
@@ -3411,6 +3287,7 @@ static int compat_sock_ioctl_trans(struct file *file, struct socket *sock,
return sock->ops->gettstamp(sock, argp, cmd == SIOCGSTAMP_OLD,
!COMPAT_USE_64BIT_TIME);

+ case SIOCETHTOOL:
case SIOCBONDSLAVEINFOQUERY:
case SIOCBONDINFOQUERY:
case SIOCSHWTSTAMP:
--
2.27.0

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