linux-ext4 - [PATCH] e2fsck: fix floating point precision error

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Message-ID: <550740039.484761277873680181.JavaMail.root@zmail05.collab.prod.int.phx2.redhat.com>
Date:	Wed, 30 Jun 2010 00:54:40 -0400 (EDT)
From:	Lachlan McIlroy <lmcilroy@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
Subject: [PATCH] e2fsck: fix floating point precision error

Fix floating point precision error in e2fsck.

Commit 641b66bc7ee0a880b0eb0125dff5f8ed8dd5a160 fixed a floating
point precision error which can result in a search algorithm looping
forever.  It can also result in an array index being out of bounds
and causing a segfault.  Here are two more cases that need to be
fixed.  I've just used the same fix from the that commit.

diff -up e2fsprogs-1.39/e2fsck/ea_refcount.c.orig e2fsprogs-1.39/e2fsck/ea_refcount.c
--- e2fsprogs-1.39/e2fsck/ea_refcount.c.orig	2010-06-30 11:14:51.516239079 +1000
+++ e2fsprogs-1.39/e2fsck/ea_refcount.c	2010-06-30 11:22:22.277362222 +1000
@@ -193,9 +193,14 @@ retry:
 				range = 0;
 			else if (blk > highval)
 				range = 1;
-			else 
+			else {
 				range = ((float) (blk - lowval)) /
 					(highval - lowval);
+				if (range > 0.9)
+					range = 0.9;
+				if (range < 0.1)
+					range = 0.1;
+			}
 			mid = low + ((int) (range * (high-low)));
 		}
 #endif
diff -up e2fsprogs-1.39/resize/extent.c.orig e2fsprogs-1.39/resize/extent.c
--- e2fsprogs-1.39/resize/extent.c.orig	2010-06-30 11:25:58.969188333 +1000
+++ e2fsprogs-1.39/resize/extent.c	2010-06-30 11:26:40.449327216 +1000
@@ -167,9 +167,14 @@ __u32 ext2fs_extent_translate(ext2_exten
 				range = 0;
 			else if (old_loc > highval)
 				range = 1;
-			else 
+			else {
 				range = ((float) (old_loc - lowval)) /
 					(highval - lowval);
+				if (range > 0.9)
+					range = 0.9;
+				if (range < 0.1)
+					range = 0.1;
+			}
 			mid = low + ((int) (range * (high-low)));
 		}
 #endif

Lachlan
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