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lguest: fix guest crash on non-linear addresses in gdt pvops

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Fixes guest crash 'lguest: bad read address 0x4800000 len 256'

The new per-cpu allocator ends up handing a non-linear address to
write_gdt_entry.  We do __pa() on it, and hand it to the host, which
kills us.

I've long wanted to make the hypercall "LOAD_GDT_ENTRY" to match the IDT
code, but had no pressing reason until now.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: lguest@ozlabs.org
This commit is contained in:
Rusty Russell
2009-04-19 23:14:00 -06:00
parent 88df781afb
commit a489f0b555
5 changed files with 21 additions and 17 deletions
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16
arch/x86/lguest/boot.c
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@@ -273,15 +273,15 @@ static void lguest_load_idt(const struct desc_ptr *desc)
* controls the entire thing and the Guest asks it to make changes using the
* LOAD_GDT hypercall.
*
* This is the opposite of the IDT code where we have a LOAD_IDT_ENTRY
* hypercall and use that repeatedly to load a new IDT. I don't think it
* really matters, but wouldn't it be nice if they were the same? Wouldn't
* it be even better if you were the one to send the patch to fix it?
* This is the exactly like the IDT code.
*/
static void lguest_load_gdt(const struct desc_ptr *desc)
{
BUG_ON((desc->size + 1) / 8 != GDT_ENTRIES);
kvm_hypercall2(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES);
unsigned int i;
struct desc_struct *gdt = (void *)desc->address;
for (i = 0; i < (desc->size+1)/8; i++)
kvm_hypercall3(LHCALL_LOAD_GDT_ENTRY, i, gdt[i].a, gdt[i].b);
}
/* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
@@ -291,7 +291,9 @@ static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
const void *desc, int type)
{
native_write_gdt_entry(dt, entrynum, desc, type);
kvm_hypercall2(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES);
/* Tell Host about this new entry. */
kvm_hypercall3(LHCALL_LOAD_GDT_ENTRY, entrynum,
dt[entrynum].a, dt[entrynum].b);
}
/* OK, I lied. There are three "thread local storage" GDT entries which change