From a489f0b555b753f9df8ddc24c7e74f657ef7ee7b Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Sun, 19 Apr 2009 23:14:00 -0600 Subject: lguest: fix guest crash on non-linear addresses in gdt pvops 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 Cc: lguest@ozlabs.org --- drivers/lguest/lg.h | 3 ++- drivers/lguest/segments.c | 13 +++++++------ drivers/lguest/x86/core.c | 4 ++-- 3 files changed, 11 insertions(+), 9 deletions(-) (limited to 'drivers/lguest') diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h index ac8a4a3..af92a17 100644 --- a/drivers/lguest/lg.h +++ b/drivers/lguest/lg.h @@ -158,7 +158,8 @@ void free_interrupts(void); /* segments.c: */ void setup_default_gdt_entries(struct lguest_ro_state *state); void setup_guest_gdt(struct lg_cpu *cpu); -void load_guest_gdt(struct lg_cpu *cpu, unsigned long table, u32 num); +void load_guest_gdt_entry(struct lg_cpu *cpu, unsigned int i, + u32 low, u32 hi); void guest_load_tls(struct lg_cpu *cpu, unsigned long tls_array); void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt); void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt); diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c index 4f15439..7ede64f 100644 --- a/drivers/lguest/segments.c +++ b/drivers/lguest/segments.c @@ -144,18 +144,19 @@ void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt) gdt[i] = cpu->arch.gdt[i]; } -/*H:620 This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT). - * We copy it from the Guest and tweak the entries. */ -void load_guest_gdt(struct lg_cpu *cpu, unsigned long table, u32 num) +/*H:620 This is where the Guest asks us to load a new GDT entry + * (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. */ +void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi) { /* We assume the Guest has the same number of GDT entries as the * Host, otherwise we'd have to dynamically allocate the Guest GDT. */ if (num > ARRAY_SIZE(cpu->arch.gdt)) kill_guest(cpu, "too many gdt entries %i", num); - /* We read the whole thing in, then fix it up. */ - __lgread(cpu, cpu->arch.gdt, table, num * sizeof(cpu->arch.gdt[0])); - fixup_gdt_table(cpu, 0, ARRAY_SIZE(cpu->arch.gdt)); + /* Set it up, then fix it. */ + cpu->arch.gdt[num].a = lo; + cpu->arch.gdt[num].b = hi; + fixup_gdt_table(cpu, num, num+1); /* Mark that the GDT changed so the core knows it has to copy it again, * even if the Guest is run on the same CPU. */ cpu->changed |= CHANGED_GDT; diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index d6d7ac0..1a83910 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -568,8 +568,8 @@ void __exit lguest_arch_host_fini(void) int lguest_arch_do_hcall(struct lg_cpu *cpu, struct hcall_args *args) { switch (args->arg0) { - case LHCALL_LOAD_GDT: - load_guest_gdt(cpu, args->arg1, args->arg2); + case LHCALL_LOAD_GDT_ENTRY: + load_guest_gdt_entry(cpu, args->arg1, args->arg2, args->arg3); break; case LHCALL_LOAD_IDT_ENTRY: load_guest_idt_entry(cpu, args->arg1, args->arg2, args->arg3); -- cgit v1.1