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Date: Wed, 30 Jun 2010 01:15:23 -0400 (EDT)
From: Lachlan McIlroy <lmcilroy@...hat.com>
To: Lachlan McIlroy <lmcilroy@...hat.com>
Cc: ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH V2] 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.
Version 2: this time it's a patch against latest git, sorry for that.
Signed-off-by: Lachlan McIlroy <lmcilroy@...hat.com>
diff --git a/e2fsck/ea_refcount.c b/e2fsck/ea_refcount.c
index 39f2db7..b10cfff 100644
--- a/e2fsck/ea_refcount.c
+++ b/e2fsck/ea_refcount.c
@@ -196,9 +196,14 @@ 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 --git a/resize/extent.c b/resize/extent.c
index 0da8df6..94eb689 100644
--- a/resize/extent.c
+++ b/resize/extent.c
@@ -167,9 +167,14 @@ __u64 ext2fs_extent_translate(ext2_extent extent, __u64 old_loc)
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 + ((__u64) (range * (high-low)));
}
#endif
----- "Lachlan McIlroy" <lmcilroy@...hat.com> wrote:
> 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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