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, 95 insertions, 0 deletions

diff --git a/fs/coda/coda_psdev.h b/fs/coda/coda_psdev.h
new file mode 100644
index 000000000..52da08c77
--- /dev/null
+++ b/fs/coda/coda_psdev.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __CODA_PSDEV_H
+#define __CODA_PSDEV_H
+
+#include <linux/backing-dev.h>
+#include <linux/magic.h>
+#include <linux/mutex.h>
+
+#define CODA_PSDEV_MAJOR 67
+#define MAX_CODADEVS  5	   /* how many do we allow */
+
+struct kstatfs;
+
+/* messages between coda filesystem in kernel and Venus */
+struct upc_req {
+	struct list_head	uc_chain;
+	caddr_t			uc_data;
+	u_short			uc_flags;
+	u_short			uc_inSize;  /* Size is at most 5000 bytes */
+	u_short			uc_outSize;
+	u_short			uc_opcode;  /* copied from data to save lookup */
+	int			uc_unique;
+	wait_queue_head_t	uc_sleep;   /* process' wait queue */
+};
+
+#define CODA_REQ_ASYNC  0x1
+#define CODA_REQ_READ   0x2
+#define CODA_REQ_WRITE  0x4
+#define CODA_REQ_ABORT  0x8
+
+/* communication pending/processing queues */
+struct venus_comm {
+	u_long		    vc_seq;
+	wait_queue_head_t   vc_waitq; /* Venus wait queue */
+	struct list_head    vc_pending;
+	struct list_head    vc_processing;
+	int                 vc_inuse;
+	struct super_block *vc_sb;
+	struct mutex	    vc_mutex;
+};
+
+static inline struct venus_comm *coda_vcp(struct super_block *sb)
+{
+	return (struct venus_comm *)((sb)->s_fs_info);
+}
+
+/* upcalls */
+int venus_rootfid(struct super_block *sb, struct CodaFid *fidp);
+int venus_getattr(struct super_block *sb, struct CodaFid *fid,
+		  struct coda_vattr *attr);
+int venus_setattr(struct super_block *, struct CodaFid *, struct coda_vattr *);
+int venus_lookup(struct super_block *sb, struct CodaFid *fid,
+		 const char *name, int length, int *type,
+		 struct CodaFid *resfid);
+int venus_close(struct super_block *sb, struct CodaFid *fid, int flags,
+		kuid_t uid);
+int venus_open(struct super_block *sb, struct CodaFid *fid, int flags,
+	       struct file **f);
+int venus_mkdir(struct super_block *sb, struct CodaFid *dirfid,
+		const char *name, int length,
+		struct CodaFid *newfid, struct coda_vattr *attrs);
+int venus_create(struct super_block *sb, struct CodaFid *dirfid,
+		 const char *name, int length, int excl, int mode,
+		 struct CodaFid *newfid, struct coda_vattr *attrs);
+int venus_rmdir(struct super_block *sb, struct CodaFid *dirfid,
+		const char *name, int length);
+int venus_remove(struct super_block *sb, struct CodaFid *dirfid,
+		 const char *name, int length);
+int venus_readlink(struct super_block *sb, struct CodaFid *fid,
+		   char *buffer, int *length);
+int venus_rename(struct super_block *sb, struct CodaFid *new_fid,
+		 struct CodaFid *old_fid, size_t old_length,
+		 size_t new_length, const char *old_name,
+		 const char *new_name);
+int venus_link(struct super_block *sb, struct CodaFid *fid,
+		  struct CodaFid *dirfid, const char *name, int len );
+int venus_symlink(struct super_block *sb, struct CodaFid *fid,
+		  const char *name, int len, const char *symname, int symlen);
+int venus_access(struct super_block *sb, struct CodaFid *fid, int mask);
+int venus_pioctl(struct super_block *sb, struct CodaFid *fid,
+		 unsigned int cmd, struct PioctlData *data);
+int coda_downcall(struct venus_comm *vcp, int opcode, union outputArgs *out,
+		  size_t nbytes);
+int venus_fsync(struct super_block *sb, struct CodaFid *fid);
+int venus_statfs(struct dentry *dentry, struct kstatfs *sfs);
+int venus_access_intent(struct super_block *sb, struct CodaFid *fid,
+			bool *access_intent_supported,
+			size_t count, loff_t ppos, int type);
+
+/*
+ * Statistics
+ */
+
+extern struct venus_comm coda_comms[];
+#endif