From: Theodore Ts'o <tytso@mit.edu>
Date: Wed, 31 Aug 2011 18:27:21 +0000 (-0400)
Subject: libext2fs: fix binary search for the icount and badblocks stores
X-Git-Tag: v1.42-WIP-0916~31
X-Git-Url: https://git.whamcloud.com/?a=commitdiff_plain;h=a4aff9ca5bcc3df76dcb3d49765674feba3d7654;p=tools%2Fe2fsprogs.git

libext2fs: fix binary search for the icount and badblocks stores

Remove the interpolation because there is a bug in icount which can
cause a core dump if calculated range gets turned into a NaN and then
do an out-of-bounds array access.  We could fix this with some more
tests, but the complexity is such that nuking all of the interpolation
code will be faster than fixing the interpolation.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---

diff --git a/lib/ext2fs/badblocks.c b/lib/ext2fs/badblocks.c
index 5eb28b7..4312e19 100644
--- a/lib/ext2fs/badblocks.c
+++ b/lib/ext2fs/badblocks.c
@@ -177,7 +177,7 @@ int ext2fs_u32_list_find(ext2_u32_list bb, __u32 blk)
 		return high;
 
 	while (low < high) {
-		mid = (low+high)/2;
+		mid = ((unsigned)low + (unsigned)high)/2;
 		if (mid == low || mid == high)
 			break;
 		if (blk == bb->list[mid])
diff --git a/lib/ext2fs/icount.c b/lib/ext2fs/icount.c
index 43cc53e..9223f66 100644
--- a/lib/ext2fs/icount.c
+++ b/lib/ext2fs/icount.c
@@ -363,31 +363,7 @@ static struct ext2_icount_el *get_icount_el(ext2_icount_t icount,
 	low = 0;
 	high = (int) icount->count-1;
 	while (low <= high) {
-#if 0
-		mid = (low+high)/2;
-#else
-		if (low == high)
-			mid = low;
-		else {
-			/* Interpolate for efficiency */
-			lowval = icount->list[low].ino;
-			highval = icount->list[high].ino;
-
-			if (ino < lowval)
-				range = 0;
-			else if (ino > highval)
-				range = 1;
-			else {
-				range = ((float) (ino - lowval)) /
-					(highval - lowval);
-				if (range > 0.9)
-					range = 0.9;
-				if (range < 0.1)
-					range = 0.1;
-			}
-			mid = low + ((int) (range * (high-low)));
-		}
-#endif
+		mid = ((unsigned)low + (unsigned)high) >> 1;
 		if (ino == icount->list[mid].ino) {
 			icount->cursor = mid+1;
 			return &icount->list[mid];