[PATCH] x86, Fix broken LDT access in VMI

[PATCH] x86, Fix broken LDT access in VMI

[Zachary Amsden]

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This one took a long time to rear up because LDT usage is not very
common, but the bug is quite serious.  It got introduced along with
another bug, already fixed, by 75b8bb3e56ca09a467fbbe5229bc68627f7445be 

Please apply.  Fix should also be headed for stable tree and backported,
it is really sadly trivial.  Glauber, Ingo, sorry for the offlist
posting, somehow the original missed LKML.

Zach

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After investigating a JRE failure, I found this bug was introduced a long time
ago, and had already managed to survive another bugfix which occurred on the
same line.  The result is a total failure of the JRE due to LDT selectors not
working properly.

Signed-off-by: Zachary Amsden <zach@vmware.com>

diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
index 040a95e..411e34f 100644
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -234,7 +234,7 @@ static void vmi_write_ldt_entry(struct desc_struct *dt, int entry,
 				const void *desc)
 {
 	u32 *ldt_entry = (u32 *)desc;
-	vmi_ops.write_idt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);
+	vmi_ops.write_ldt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);
 }
 
 static void vmi_load_sp0(struct tss_struct *tss,

Re: [PATCH] x86, Fix broken LDT access in VMI

[Ingo Molnar]

* Zachary Amsden <zach@vmware.com> wrote:

> This one took a long time to rear up because LDT usage is not very
> common, but the bug is quite serious.  It got introduced along with
> another bug, already fixed, by 75b8bb3e56ca09a467fbbe5229bc68627f7445be 
> 
> Please apply.  Fix should also be headed for stable tree and backported,
> it is really sadly trivial.  Glauber, Ingo, sorry for the offlist
> posting, somehow the original missed LKML.

> -	vmi_ops.write_idt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);
> +	vmi_ops.write_ldt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);

oops. Applied to tip/x86/urgent, thanks Zachary!

	Ingo

Re: [PATCH] x86, Fix broken LDT access in VMI

[Parag Warudkar]

On Tue, Sep 30, 2008 at 3:13 PM, Ingo Molnar <mingo@elte.hu> wrote:
>> -     vmi_ops.write_idt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);
>> +     vmi_ops.write_ldt_entry(dt, entry, ldt_entry[0], ldt_entry[1]);

For a few seconds I thought it was diff going mad diff'ing exactly
similar lines.

This one could actually use some capitalization to reduce the
possibility of similar problems in future - rename to write_IDT_entry
and write_LDT_entry perhaps?

Parag