[PATCH 4.2.y-ckt 099/211] lib/hexdump.c: truncate output in case of overflow

[Kamal Mostafa]

4.2.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Shevchenko <andriy.shevchenko at linux.intel.com>

commit 9f029f540c2f7e010e4922d44ba0dfd05da79f88 upstream.

There is a classical off-by-one error in case when we try to place, for
example, 1+1 bytes as hex in the buffer of size 6.  The expected result is
to get an output truncated, but in the reality we get 6 bytes filed
followed by terminating NUL.

Change the logic how we fill the output in case of byte dumping into
limited space.  This will follow the snprintf() behaviour by truncating
output even on half bytes.

Fixes: 114fc1afb2de (hexdump: make it return number of bytes placed in buffer)
Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
Reported-by: Aaro Koskinen <aaro.koskinen at nokia.com>
Tested-by: Aaro Koskinen <aaro.koskinen at nokia.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 lib/hexdump.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/hexdump.c b/lib/hexdump.c
index 8d74c20..992457b 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -169,11 +169,15 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize,
 		}
 	} else {
 		for (j = 0; j < len; j++) {
-			if (linebuflen < lx + 3)
+			if (linebuflen < lx + 2)
 				goto overflow2;
 			ch = ptr[j];
 			linebuf[lx++] = hex_asc_hi(ch);
+			if (linebuflen < lx + 2)
+				goto overflow2;
 			linebuf[lx++] = hex_asc_lo(ch);
+			if (linebuflen < lx + 2)
+				goto overflow2;
 			linebuf[lx++] = ' ';
 		}
 		if (j)
-- 
1.9.1