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[PULL,3/3] kvmvapic: Prevent reading beyond the end of guest RAM

Message ID 1382108641-4862-4-git-send-email-pbonzini@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Paolo Bonzini Oct. 18, 2013, 3:04 p.m. UTC 
From: Jan Kiszka <jan.kiszka@siemens.com>

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 <jan.kiszka@siemens.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
 hw/i386/kvmvapic.c | 3 +++
 1 file changed, 3 insertions(+)
diff mbox

Patch

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) {