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, 113 insertions, 0 deletions

diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
new file mode 100644
index 000000000..5f1f969f4
--- /dev/null
+++ b/fs/udf/ialloc.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ialloc.c
+ *
+ * PURPOSE
+ *	Inode allocation handling routines for the OSTA-UDF(tm) filesystem.
+ *
+ * COPYRIGHT
+ *  (C) 1998-2001 Ben Fennema
+ *
+ * HISTORY
+ *
+ *  02/24/99 blf  Created.
+ *
+ */
+
+#include "udfdecl.h"
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "udf_i.h"
+#include "udf_sb.h"
+
+void udf_free_inode(struct inode *inode)
+{
+	udf_free_blocks(inode->i_sb, NULL, &UDF_I(inode)->i_location, 0, 1);
+}
+
+struct inode *udf_new_inode(struct inode *dir, umode_t mode)
+{
+	struct super_block *sb = dir->i_sb;
+	struct udf_sb_info *sbi = UDF_SB(sb);
+	struct inode *inode;
+	udf_pblk_t block;
+	uint32_t start = UDF_I(dir)->i_location.logicalBlockNum;
+	struct udf_inode_info *iinfo;
+	struct udf_inode_info *dinfo = UDF_I(dir);
+	int err;
+
+	inode = new_inode(sb);
+
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	iinfo = UDF_I(inode);
+	if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_EXTENDED_FE)) {
+		iinfo->i_efe = 1;
+		if (UDF_VERS_USE_EXTENDED_FE > sbi->s_udfrev)
+			sbi->s_udfrev = UDF_VERS_USE_EXTENDED_FE;
+		iinfo->i_data = kzalloc(inode->i_sb->s_blocksize -
+					sizeof(struct extendedFileEntry),
+					GFP_KERNEL);
+	} else {
+		iinfo->i_efe = 0;
+		iinfo->i_data = kzalloc(inode->i_sb->s_blocksize -
+					sizeof(struct fileEntry),
+					GFP_KERNEL);
+	}
+	if (!iinfo->i_data) {
+		make_bad_inode(inode);
+		iput(inode);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	err = -ENOSPC;
+	block = udf_new_block(dir->i_sb, NULL,
+			      dinfo->i_location.partitionReferenceNum,
+			      start, &err);
+	if (err) {
+		make_bad_inode(inode);
+		iput(inode);
+		return ERR_PTR(err);
+	}
+
+	iinfo->i_unique = lvid_get_unique_id(sb);
+	inode->i_generation = iinfo->i_unique;
+
+	inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+	if (UDF_QUERY_FLAG(sb, UDF_FLAG_UID_SET))
+		inode->i_uid = sbi->s_uid;
+	if (UDF_QUERY_FLAG(sb, UDF_FLAG_GID_SET))
+		inode->i_gid = sbi->s_gid;
+
+	iinfo->i_location.logicalBlockNum = block;
+	iinfo->i_location.partitionReferenceNum =
+				dinfo->i_location.partitionReferenceNum;
+	inode->i_ino = udf_get_lb_pblock(sb, &iinfo->i_location, 0);
+	inode->i_blocks = 0;
+	iinfo->i_lenEAttr = 0;
+	iinfo->i_lenAlloc = 0;
+	iinfo->i_use = 0;
+	iinfo->i_checkpoint = 1;
+	iinfo->i_extraPerms = FE_PERM_U_CHATTR;
+	udf_update_extra_perms(inode, mode);
+
+	if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_AD_IN_ICB))
+		iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
+	else if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
+		iinfo->i_alloc_type = ICBTAG_FLAG_AD_SHORT;
+	else
+		iinfo->i_alloc_type = ICBTAG_FLAG_AD_LONG;
+	simple_inode_init_ts(inode);
+	iinfo->i_crtime = inode_get_mtime(inode);
+	if (unlikely(insert_inode_locked(inode) < 0)) {
+		make_bad_inode(inode);
+		iput(inode);
+		return ERR_PTR(-EIO);
+	}
+	mark_inode_dirty(inode);
+
+	return inode;
+}