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Date: Wed, 6 Dec 2017 02:33:44 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: kernel-hardening@...ts.openwall.com,
Kees Cook <keescook@...omium.org>,
PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
Ingo Molnar <mingo@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Tycho Andersen <tycho@...ho.ws>,
Laura Abbott <labbott@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Borislav Petkov <bp@...en8.de>,
Thomas Gleixner <tglx@...utronix.de>,
"H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
x86@...nel.org,
alex.popov@...ux.com
Subject: [PATCH RFC v6 3/6] x86/entry: Erase kernel stack in syscall_trace_enter()
Make STACKLEAK erase kernel stack after ptrace/seccomp/auditing
not to leave any sensitive information on the stack for the syscall code.
This code is modified from Brad Spengler/PaX Team's code in the last
public patch of grsecurity/PaX based on our understanding of the code.
Changes or omissions from the original code are ours and don't reflect
the original grsecurity/PaX code.
Signed-off-by: Alexander Popov <alex.popov@...ux.com>
---
arch/x86/entry/common.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index d7d3cc2..d45b7cf 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -45,6 +45,12 @@ __visible inline void enter_from_user_mode(void)
static inline void enter_from_user_mode(void) {}
#endif
+#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+asmlinkage void erase_kstack(void);
+#else
+static void erase_kstack(void) {}
+#endif
+
static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
{
#ifdef CONFIG_X86_64
@@ -81,11 +87,15 @@ static long syscall_trace_enter(struct pt_regs *regs)
emulated = true;
if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs)) {
+ erase_kstack();
return -1L;
+ }
- if (emulated)
+ if (emulated) {
+ erase_kstack();
return -1L;
+ }
#ifdef CONFIG_SECCOMP
/*
@@ -117,8 +127,10 @@ static long syscall_trace_enter(struct pt_regs *regs)
}
ret = __secure_computing(&sd);
- if (ret == -1)
+ if (ret == -1) {
+ erase_kstack();
return ret;
+ }
}
#endif
@@ -127,6 +139,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
do_audit_syscall_entry(regs, arch);
+ erase_kstack();
return ret ?: regs->orig_ax;
}
--
2.7.4
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