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, 172 insertions, 0 deletions

diff --git a/arch/alpha/boot/misc.c b/arch/alpha/boot/misc.c
new file mode 100644
index 000000000..1ab91852d
--- /dev/null
+++ b/arch/alpha/boot/misc.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * misc.c
+ * 
+ * This is a collection of several routines from gzip-1.0.3 
+ * adapted for Linux.
+ *
+ * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
+ *
+ * Modified for ARM Linux by Russell King
+ *
+ * Nicolas Pitre <nico@visuaide.com>  1999/04/14 :
+ *  For this code to run directly from Flash, all constant variables must
+ *  be marked with 'const' and all other variables initialized at run-time 
+ *  only.  This way all non constant variables will end up in the bss segment,
+ *  which should point to addresses in RAM and cleared to 0 on start.
+ *  This allows for a much quicker boot time.
+ *
+ * Modified for Alpha, from the ARM version, by Jay Estabrook 2003.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include <linux/uaccess.h>
+
+#define memzero(s,n)	memset ((s),0,(n))
+#define puts		srm_printk
+extern long srm_printk(const char *, ...)
+     __attribute__ ((format (printf, 1, 2)));
+
+/*
+ * gzip declarations
+ */
+#define OF(args)  args
+#define STATIC static
+
+typedef unsigned char  uch;
+typedef unsigned short ush;
+typedef unsigned long  ulg;
+
+#define WSIZE 0x8000		/* Window size must be at least 32k, */
+				/* and a power of two */
+
+static uch *inbuf;		/* input buffer */
+static uch *window;		/* Sliding window buffer */
+
+static unsigned insize;		/* valid bytes in inbuf */
+static unsigned inptr;		/* index of next byte to be processed in inbuf */
+static unsigned outcnt;		/* bytes in output buffer */
+
+/* gzip flag byte */
+#define ASCII_FLAG   0x01 /* bit 0 set: file probably ascii text */
+#define CONTINUATION 0x02 /* bit 1 set: continuation of multi-part gzip file */
+#define EXTRA_FIELD  0x04 /* bit 2 set: extra field present */
+#define ORIG_NAME    0x08 /* bit 3 set: original file name present */
+#define COMMENT      0x10 /* bit 4 set: file comment present */
+#define ENCRYPTED    0x20 /* bit 5 set: file is encrypted */
+#define RESERVED     0xC0 /* bit 6,7:   reserved */
+
+#define get_byte()  (inptr < insize ? inbuf[inptr++] : fill_inbuf())
+
+/* Diagnostic functions */
+#ifdef DEBUG
+#  define Assert(cond,msg) {if(!(cond)) error(msg);}
+#  define Trace(x) fprintf x
+#  define Tracev(x) {if (verbose) fprintf x ;}
+#  define Tracevv(x) {if (verbose>1) fprintf x ;}
+#  define Tracec(c,x) {if (verbose && (c)) fprintf x ;}
+#  define Tracecv(c,x) {if (verbose>1 && (c)) fprintf x ;}
+#else
+#  define Assert(cond,msg)
+#  define Trace(x)
+#  define Tracev(x)
+#  define Tracevv(x)
+#  define Tracec(c,x)
+#  define Tracecv(c,x)
+#endif
+
+static int  fill_inbuf(void);
+static void flush_window(void);
+static void error(char *m);
+
+static char *input_data;
+static int  input_data_size;
+
+static uch *output_data;
+static ulg output_ptr;
+static ulg bytes_out;
+
+static void error(char *m);
+
+extern int end;
+static ulg free_mem_ptr;
+static ulg free_mem_end_ptr;
+
+#define HEAP_SIZE 0x3000
+
+#include "../../../lib/inflate.c"
+
+/* ===========================================================================
+ * Fill the input buffer. This is called only when the buffer is empty
+ * and at least one byte is really needed.
+ */
+int fill_inbuf(void)
+{
+	if (insize != 0)
+		error("ran out of input data");
+
+	inbuf = input_data;
+	insize = input_data_size;
+
+	inptr = 1;
+	return inbuf[0];
+}
+
+/* ===========================================================================
+ * Write the output window window[0..outcnt-1] and update crc and bytes_out.
+ * (Used for the decompressed data only.)
+ */
+void flush_window(void)
+{
+	ulg c = crc;
+	unsigned n;
+	uch *in, *out, ch;
+
+	in = window;
+	out = &output_data[output_ptr];
+	for (n = 0; n < outcnt; n++) {
+		ch = *out++ = *in++;
+		c = crc_32_tab[((int)c ^ ch) & 0xff] ^ (c >> 8);
+	}
+	crc = c;
+	bytes_out += (ulg)outcnt;
+	output_ptr += (ulg)outcnt;
+	outcnt = 0;
+/*	puts("."); */
+}
+
+static void error(char *x)
+{
+	puts("\n\n");
+	puts(x);
+	puts("\n\n -- System halted");
+
+	while(1);	/* Halt */
+}
+
+unsigned int
+decompress_kernel(void *output_start,
+		  void *input_start,
+		  size_t ksize,
+		  size_t kzsize)
+{
+	output_data		= (uch *)output_start;
+	input_data		= (uch *)input_start;
+	input_data_size		= kzsize; /* use compressed size */
+
+	/* FIXME FIXME FIXME */
+	free_mem_ptr		= (ulg)output_start + ksize;
+	free_mem_end_ptr	= (ulg)output_start + ksize + 0x200000;
+	/* FIXME FIXME FIXME */
+
+	/* put in temp area to reduce initial footprint */
+	window = malloc(WSIZE);
+
+	makecrc();
+/*	puts("Uncompressing Linux..."); */
+	gunzip();
+/*	puts(" done, booting the kernel.\n"); */
+	return output_ptr;
+}