hexdump: fix for non-aligned buffers

A hexdump with a buf not aligned to the groupsize causes
non-naturally-aligned memory accesses.  This was causing a kernel panic
on the processor BlackFin BF527, when such an unaligned buffer was fed
by the function ubifs_scanned_corruption in fs/ubifs/scan.c .

To fix this, change accesses to the contents of the buffer so they go
through get_unaligned().  This change should be harmless to unaligned-
access-capable architectures, and any performance hit should be anyway
dwarfed by the snprintf() processing time.

Signed-off-by: Horacio Mijail Antón Quiles <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: David Howells <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Joe Perches <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

lib/hexdump.c

@@ -11,6 +11,7 @@
 #include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
+#include <asm/unaligned.h>
 
 const char hex_asc[] = "0123456789abcdef";
 EXPORT_SYMBOL(hex_asc);
@@ -139,7 +140,7 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
 				       "%s%16.16llx", j ? " " : "",
-				       (unsigned long long)*(ptr8 + j));
+				       get_unaligned(ptr8 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
 			lx += ret;
@@ -150,7 +151,7 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
 				       "%s%8.8x", j ? " " : "",
-				       *(ptr4 + j));
+				       get_unaligned(ptr4 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
 			lx += ret;
@@ -161,7 +162,7 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 		for (j = 0; j < ngroups; j++) {
 			ret = snprintf(linebuf + lx, linebuflen - lx,
 				       "%s%4.4x", j ? " " : "",
-				       *(ptr2 + j));
+				       get_unaligned(ptr2 + j));
 			if (ret >= linebuflen - lx)
 				goto overflow1;
 			lx += ret;