linux-kernel - [PATCH v13 07/16] x86/process/64: Use FSGSBASE instructions on thread copy and ptrace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200528201402.1708239-8-sashal@kernel.org>
Date:   Thu, 28 May 2020 16:13:53 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     tglx@...utronix.de, luto@...nel.org, ak@...ux.intel.com
Cc:     corbet@....net, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        shuah@...nel.org, gregkh@...uxfoundation.org, tony.luck@...el.com,
        chang.seok.bae@...el.com, dave.hansen@...ux.intel.com,
        peterz@...radead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, jarkko.sakkinen@...ux.intel.com,
        "H . Peter Anvin" <hpa@...or.com>,
        Ravi Shankar <ravi.v.shankar@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH v13 07/16] x86/process/64: Use FSGSBASE instructions on thread copy and ptrace

From: "Chang S. Bae" <chang.seok.bae@...el.com>

When FSGSBASE is enabled, copying threads and reading fsbase and gsbase
using ptrace must read the actual values.

When copying a thread, use save_fsgs() and copy the saved values.  For
ptrace, the bases must be read from memory regardless of the selector if
FSGSBASE is enabled.

[ tglx: Invoke __rdgsbase_inactive() with interrupts disabled ]
[ luto: Massage changelog ]

Suggested-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Link: https://lkml.kernel.org/r/1557309753-24073-9-git-send-email-chang.seok.bae@intel.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/process.c    | 10 ++++++----
 arch/x86/kernel/process_64.c |  6 ++++--
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9da70b279dad..0264d9bb8991 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -140,10 +140,12 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 
 #ifdef CONFIG_X86_64
-	savesegment(gs, p->thread.gsindex);
-	p->thread.gsbase = p->thread.gsindex ? 0 : current->thread.gsbase;
-	savesegment(fs, p->thread.fsindex);
-	p->thread.fsbase = p->thread.fsindex ? 0 : current->thread.fsbase;
+	current_save_fsgs();
+	p->thread.fsindex = current->thread.fsindex;
+	p->thread.fsbase = current->thread.fsbase;
+	p->thread.gsindex = current->thread.gsindex;
+	p->thread.gsbase = current->thread.gsbase;
+
 	savesegment(es, p->thread.es);
 	savesegment(ds, p->thread.ds);
 #else
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index aefb30bc56bc..0bcb48a1264a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -423,7 +423,8 @@ unsigned long x86_fsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		fsbase = x86_fsbase_read_cpu();
-	else if (task->thread.fsindex == 0)
+	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+		 (task->thread.fsindex == 0))
 		fsbase = task->thread.fsbase;
 	else
 		fsbase = x86_fsgsbase_read_task(task, task->thread.fsindex);
@@ -437,7 +438,8 @@ unsigned long x86_gsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		gsbase = x86_gsbase_read_cpu_inactive();
-	else if (task->thread.gsindex == 0)
+	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+		 (task->thread.gsindex == 0))
 		gsbase = task->thread.gsbase;
 	else
 		gsbase = x86_fsgsbase_read_task(task, task->thread.gsindex);
-- 
2.25.1