linux-kernel - [PATCH]: xarray: Fix potential out of bounds access

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Message-ID: <20190114184741.GF17906@uranus.lan>
Date:   Mon, 14 Jan 2019 21:47:41 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH]: xarray: Fix potential out of bounds access

Since the mark is used as an array index we should use
preincrement to not access the XA_MARK_MAX index.

Cc: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
---
Matthew, take a look please, I suspect we may access the
mark index out of allocated one. Compile tested only.
It comes from 58d6ea3085f2e53714810a513c61629f6d2be0a6

 lib/xarray.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-next.git/lib/xarray.c
===================================================================
--- linux-next.git.orig/lib/xarray.c
+++ linux-next.git/lib/xarray.c
@@ -129,7 +129,7 @@ static void xas_squash_marks(const struc
 			continue;
 		__set_bit(xas->xa_offset, marks);
 		bitmap_clear(marks, xas->xa_offset + 1, xas->xa_sibs);
-	} while (mark++ != (__force unsigned)XA_MARK_MAX);
+	} while (++mark != (__force unsigned)XA_MARK_MAX);
 }
 
 /* extracts the offset within this node from the index */