From: Juergen Gross jgross@suse.com
[ 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 jgross@suse.com Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/r/20220630071441.28576-3-jgross@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/head64.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index de01903c3735..5036104d5470 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)