linux-kernel - [Linux-kernel-mentees] [PATCH] ptrace: Prevent kernel-infoleak in ptrace_get_syscall

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Message-Id: <20200727213644.328662-1-yepeilin.cs@gmail.com>
Date:   Mon, 27 Jul 2020 17:36:44 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Peilin Ye <yepeilin.cs@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-kernel@...r.kernel.org
Subject: [Linux-kernel-mentees] [PATCH] ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()

ptrace_get_syscall_info() is copying uninitialized stack memory to
userspace due to the compiler not initializing holes in statically
allocated structures. Fix it by initializing `info` with memset().

Cc: stable@...r.kernel.org
Fixes: 201766a20e30 ("ptrace: add PTRACE_GET_SYSCALL_INFO request")
Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
---
 kernel/ptrace.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 43d6179508d6..e48d05b765b5 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -960,15 +960,17 @@ ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
 			void __user *datavp)
 {
 	struct pt_regs *regs = task_pt_regs(child);
-	struct ptrace_syscall_info info = {
-		.op = PTRACE_SYSCALL_INFO_NONE,
-		.arch = syscall_get_arch(child),
-		.instruction_pointer = instruction_pointer(regs),
-		.stack_pointer = user_stack_pointer(regs),
-	};
+	struct ptrace_syscall_info info;
 	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
 	unsigned long write_size;
 
+	memset(&info, 0, sizeof(info));
+
+	info.op	= PTRACE_SYSCALL_INFO_NONE;
+	info.arch = syscall_get_arch(child);
+	info.instruction_pointer = instruction_pointer(regs);
+	info.stack_pointer = user_stack_pointer(regs);
+
 	/*
 	 * This does not need lock_task_sighand() to access
 	 * child->last_siginfo because ptrace_freeze_traced()
-- 
2.25.1