From: Andrew Cooper Date: Tue, 9 Feb 2021 22:10:54 +0000 (+0000) Subject: x86/ucode/amd: Fix OoB read in cpu_request_microcode() X-Git-Tag: archive/raspbian/4.16.0+51-g0941d6cb-1+rpi1~2^2~42^2~913 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=1cbc4d89c45cba3929f1c0cb4bca0b000c4f174b;p=xen.git x86/ucode/amd: Fix OoB read in cpu_request_microcode() verify_patch_size() is a maximum size check, and doesn't have a minimum bound. If the microcode container encodes a blob with a length less than 64 bytes, the subsequent calls to microcode_fits()/compare_header() may read off the end of the buffer. Fixes: 4de936a38a ("x86/ucode/amd: Rework parsing logic in cpu_request_microcode()") Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c index 5255028af7..3e51e53c1f 100644 --- a/xen/arch/x86/cpu/microcode/amd.c +++ b/xen/arch/x86/cpu/microcode/amd.c @@ -349,6 +349,7 @@ static struct microcode_patch *cpu_request_microcode(const void *buf, size_t siz if ( size < sizeof(*mc) || (mc = buf)->type != UCODE_UCODE_TYPE || size - sizeof(*mc) < mc->len || + mc->len < sizeof(struct microcode_patch) || (!skip_ucode && !verify_patch_size(mc->len)) ) { printk(XENLOG_ERR "microcode: Bad microcode data\n");