openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 139 insertions, 0 deletions

diff --git a/fs/orangefs/dcache.c b/fs/orangefs/dcache.c
new file mode 100644
index 000000000..a19d1ad70
--- /dev/null
+++ b/fs/orangefs/dcache.c
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) 2001 Clemson University and The University of Chicago
+ *
+ * See COPYING in top-level directory.
+ */
+
+/*
+ *  Implementation of dentry (directory cache) functions.
+ */
+
+#include "protocol.h"
+#include "orangefs-kernel.h"
+
+/* Returns 1 if dentry can still be trusted, else 0. */
+static int orangefs_revalidate_lookup(struct inode *parent_inode, const struct qstr *name,
+				      struct dentry *dentry)
+{
+	struct orangefs_inode_s *parent = ORANGEFS_I(parent_inode);
+	struct inode *inode = dentry->d_inode;
+	struct orangefs_kernel_op_s *new_op;
+	int ret = 0;
+	int err = 0;
+
+	gossip_debug(GOSSIP_DCACHE_DEBUG, "%s: attempting lookup.\n", __func__);
+
+	new_op = op_alloc(ORANGEFS_VFS_OP_LOOKUP);
+	if (!new_op)
+		return -ENOMEM;
+
+	new_op->upcall.req.lookup.sym_follow = ORANGEFS_LOOKUP_LINK_NO_FOLLOW;
+	new_op->upcall.req.lookup.parent_refn = parent->refn;
+	/* op_alloc() leaves ->upcall zeroed */
+	memcpy(new_op->upcall.req.lookup.d_name, name->name,
+			min(name->len, ORANGEFS_NAME_MAX - 1));
+
+	gossip_debug(GOSSIP_DCACHE_DEBUG,
+		     "%s:%s:%d interrupt flag [%d]\n",
+		     __FILE__,
+		     __func__,
+		     __LINE__,
+		     get_interruptible_flag(parent_inode));
+
+	err = service_operation(new_op, "orangefs_lookup",
+			get_interruptible_flag(parent_inode));
+
+	/* Positive dentry: reject if error or not the same inode. */
+	if (inode) {
+		if (err) {
+			gossip_debug(GOSSIP_DCACHE_DEBUG,
+			    "%s:%s:%d lookup failure.\n",
+			    __FILE__, __func__, __LINE__);
+			goto out_drop;
+		}
+		if (!match_handle(new_op->downcall.resp.lookup.refn.khandle,
+		    inode)) {
+			gossip_debug(GOSSIP_DCACHE_DEBUG,
+			    "%s:%s:%d no match.\n",
+			    __FILE__, __func__, __LINE__);
+			goto out_drop;
+		}
+
+	/* Negative dentry: reject if success or error other than ENOENT. */
+	} else {
+		gossip_debug(GOSSIP_DCACHE_DEBUG, "%s: negative dentry.\n",
+		    __func__);
+		if (!err || err != -ENOENT) {
+			if (new_op->downcall.status != 0)
+				gossip_debug(GOSSIP_DCACHE_DEBUG,
+				    "%s:%s:%d lookup failure.\n",
+				    __FILE__, __func__, __LINE__);
+			goto out_drop;
+		}
+	}
+
+	orangefs_set_timeout(dentry);
+	ret = 1;
+out_release_op:
+	op_release(new_op);
+	return ret;
+out_drop:
+	gossip_debug(GOSSIP_DCACHE_DEBUG, "%s:%s:%d revalidate failed\n",
+	    __FILE__, __func__, __LINE__);
+	goto out_release_op;
+}
+
+/*
+ * Verify that dentry is valid.
+ *
+ * Should return 1 if dentry can still be trusted, else 0.
+ */
+static int orangefs_d_revalidate(struct inode *dir, const struct qstr *name,
+				 struct dentry *dentry, unsigned int flags)
+{
+	int ret;
+	unsigned long time = (unsigned long) dentry->d_fsdata;
+
+	if (time_before(jiffies, time))
+		return 1;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	gossip_debug(GOSSIP_DCACHE_DEBUG, "%s: called on dentry %p.\n",
+		     __func__, dentry);
+
+	/* skip root handle lookups. */
+	if (dentry->d_inode && is_root_handle(dentry->d_inode))
+		return 1;
+
+	/*
+	 * If this passes, the positive dentry still exists or the negative
+	 * dentry still does not exist.
+	 */
+	if (!orangefs_revalidate_lookup(dir, name, dentry))
+		return 0;
+
+	/* We do not need to continue with negative dentries. */
+	if (!dentry->d_inode) {
+		gossip_debug(GOSSIP_DCACHE_DEBUG,
+		    "%s: negative dentry or positive dentry and inode valid.\n",
+		    __func__);
+		return 1;
+	}
+
+	/* Now we must perform a getattr to validate the inode contents. */
+
+	ret = orangefs_inode_check_changed(dentry->d_inode);
+	if (ret < 0) {
+		gossip_debug(GOSSIP_DCACHE_DEBUG, "%s:%s:%d getattr failure.\n",
+		    __FILE__, __func__, __LINE__);
+		return 0;
+	}
+	return !ret;
+}
+
+const struct dentry_operations orangefs_dentry_operations = {
+	.d_revalidate = orangefs_d_revalidate,
+};