[Qemu-devel] [PATCH uq/master] kvmvapic: Prevent reading beyond the end of guest RAM

2013-09-30 Thread Jan Kiszka 
rom_state_paddr is guest provided (caller address of outw(VAPIC_PORT) +
writen 16-bit value) and can be influenced to point beyond the end of
the host memory backing the guest's RAM. Make sure we do not use this
pointer to actually read beyond the limits.

Reading arbitrary guest bytes is harmless, the guest kernel has to
manage access to this I/O port anyway.

Signed-off-by: Jan Kiszka 
---
 hw/i386/kvmvapic.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
index 1c2dbf5..2d87600 100644
--- a/hw/i386/kvmvapic.c
+++ b/hw/i386/kvmvapic.c
@@ -596,6 +596,9 @@ static int vapic_map_rom_writable(VAPICROMState *s)
 section = memory_region_find(as, 0, 1);
 
 /* read ROM size from RAM region */
+if (rom_paddr + 2 >= memory_region_size(section.mr)) {
+return -1;
+}
 ram = memory_region_get_ram_ptr(section.mr);
 rom_size = ram[rom_paddr + 2] * ROM_BLOCK_SIZE;
 if (rom_size == 0) {
-- 
1.8.1.1.298.ge7eed54

Re: [Qemu-devel] [PATCH uq/master] kvmvapic: Prevent reading beyond the end of guest RAM

2013-10-04 Thread Gleb Natapov 
On Mon, Sep 30, 2013 at 12:35:13PM +0200, Jan Kiszka wrote:
> rom_state_paddr is guest provided (caller address of outw(VAPIC_PORT) +
> writen 16-bit value) and can be influenced to point beyond the end of
> the host memory backing the guest's RAM. Make sure we do not use this
> pointer to actually read beyond the limits.
> 
> Reading arbitrary guest bytes is harmless, the guest kernel has to
> manage access to this I/O port anyway.
> 
> Signed-off-by: Jan Kiszka 
Applied, thanks.

> ---
>  hw/i386/kvmvapic.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
> index 1c2dbf5..2d87600 100644
> --- a/hw/i386/kvmvapic.c
> +++ b/hw/i386/kvmvapic.c
> @@ -596,6 +596,9 @@ static int vapic_map_rom_writable(VAPICROMState *s)
>  section = memory_region_find(as, 0, 1);
>  
>  /* read ROM size from RAM region */
> +if (rom_paddr + 2 >= memory_region_size(section.mr)) {
> +return -1;
> +}
>  ram = memory_region_get_ram_ptr(section.mr);
>  rom_size = ram[rom_paddr + 2] * ROM_BLOCK_SIZE;
>  if (rom_size == 0) {
> -- 
> 1.8.1.1.298.ge7eed54

--
Gleb.

Re: [Qemu-devel] [PATCH uq/master] kvmvapic: Prevent reading beyond the end of guest RAM

2013-09-30 Thread Michael S. Tsirkin 
On Mon, Sep 30, 2013 at 12:35:13PM +0200, Jan Kiszka wrote:
> rom_state_paddr is guest provided (caller address of outw(VAPIC_PORT) +
> writen 16-bit value) and can be influenced to point beyond the end of
> the host memory backing the guest's RAM. Make sure we do not use this
> pointer to actually read beyond the limits.
> 
> Reading arbitrary guest bytes is harmless, the guest kernel has to
> manage access to this I/O port anyway.
> 
> Signed-off-by: Jan Kiszka 

Acked-by: Michael S. Tsirkin 

> ---
>  hw/i386/kvmvapic.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
> index 1c2dbf5..2d87600 100644
> --- a/hw/i386/kvmvapic.c
> +++ b/hw/i386/kvmvapic.c
> @@ -596,6 +596,9 @@ static int vapic_map_rom_writable(VAPICROMState *s)
>  section = memory_region_find(as, 0, 1);
>  
>  /* read ROM size from RAM region */
> +if (rom_paddr + 2 >= memory_region_size(section.mr)) {
> +return -1;
> +}
>  ram = memory_region_get_ram_ptr(section.mr);
>  rom_size = ram[rom_paddr + 2] * ROM_BLOCK_SIZE;
>  if (rom_size == 0) {
> -- 
> 1.8.1.1.298.ge7eed54