2010-06-30 04:54:40

by Lachlan McIlroy

[permalink] [raw]
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