From: Juergen Gross jgross@suse.com
stable inclusion from stable-4.19.253 commit 36e2f161fb01795722f2ff1a24d95f08100333dd category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5JTYM CVE: CVE-2022-36123
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[ 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 Signed-off-by: GONG, Ruiqi gongruiqi1@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- 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 88dc38b4a147..90c2613af36b 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -383,6 +383,8 @@ 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)