From: Juergen Gross Date: Thu, 30 Jun 2022 07:14:40 +0000 (+0200) Subject: x86: Clear .brk area at early boot X-Git-Tag: v5.15.73~2218 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=26bb7afc027ce6ac8ab6747babec674d55689ff0;p=platform%2Fkernel%2Flinux-rpi.git x86: Clear .brk area at early boot [ Upstream commit 38fa5479b41376dc9d7f57e71c83514285a25ca0 ] The .brk section has the same properties as .bss: it is an alloc-only section and should be cleared before being used. Not doing so is especially a problem for Xen PV guests, as the hypervisor will validate page tables (check for writable page tables and hypervisor private bits) before accepting them to be used. Make sure .brk is initially zero by letting clear_bss() clear the brk area, too. Signed-off-by: Juergen Gross Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220630071441.28576-3-jgross@suse.com Signed-off-by: Sasha Levin --- diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index de01903..5036104 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -418,6 +418,8 @@ static void __init clear_bss(void) { memset(__bss_start, 0, (unsigned long) __bss_stop - (unsigned long) __bss_start); + memset(__brk_base, 0, + (unsigned long) __brk_limit - (unsigned long) __brk_base); } static unsigned long get_cmd_line_ptr(void)