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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dan Carpenter <dan.carpenter@oracle.com>,
        Peilin Ye <yepeilin.cs@gmail.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH 5.4 01/34] ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()
Date:   Sat, 19 Dec 2020 14:02:58 +0100
Message-Id: <20201219125341.454853868@linuxfoundation.org>
In-Reply-To: <20201219125341.384025953@linuxfoundation.org>
References: <20201219125341.384025953@linuxfoundation.org>
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From: Peilin Ye <yepeilin.cs@gmail.com>

commit 0032ce0f85a269a006e91277be5fdbc05fad8426 upstream.

ptrace_get_syscall_info() is potentially copying uninitialized stack
memory to userspace, since the compiler may leave a 3-byte hole near the
beginning of `info`. Fix it by adding a padding field to `struct
ptrace_syscall_info`.

Fixes: 201766a20e30 ("ptrace: add PTRACE_GET_SYSCALL_INFO request")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Reviewed-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200801152044.230416-1-yepeilin.cs@gmail.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/uapi/linux/ptrace.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -81,7 +81,8 @@ struct seccomp_metadata {
 
 struct ptrace_syscall_info {
 	__u8 op;	/* PTRACE_SYSCALL_INFO_* */
-	__u32 arch __attribute__((__aligned__(sizeof(__u32))));
+	__u8 pad[3];
+	__u32 arch;
 	__u64 instruction_pointer;
 	__u64 stack_pointer;
 	union {