linux-kernel - [PATCH 13/13] android: ram_console: honor dmesg

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Message-Id: <1331157503-3413-14-git-send-email-john.stultz@linaro.org>
Date:	Wed,  7 Mar 2012 13:58:23 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Nick Kralevich <nnk@...gle.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	John Stultz <john.stultz@...aro.org>
Subject: [PATCH 13/13] android: ram_console: honor dmesg_restrict

From: Nick Kralevich <nnk@...gle.com>

The Linux kernel has a setting called dmesg_restrict. When true,
only processes with CAP_SYSLOG can view the kernel dmesg logs. This
helps prevent leaking of kernel information into user space.

On Android, it's possible to bypass these restrictions by viewing
/proc/last_kmsg.

This change makes /proc/last_kmsg require the same permissions as
dmesg.

Bug: 5555691
CC: Greg KH <gregkh@...uxfoundation.org>
CC: Android Kernel Team <kernel-team@...roid.com>
Change-Id: I50ecb74012ef2ac0a3cff7325192634341fddae9
Signed-off-by: Nick Kralevich <nnk@...gle.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/staging/android/ram_console.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/staging/android/ram_console.c b/drivers/staging/android/ram_console.c
index d956b84..b242be2 100644
--- a/drivers/staging/android/ram_console.c
+++ b/drivers/staging/android/ram_console.c
@@ -99,6 +99,9 @@ static ssize_t ram_console_read_old(struct file *file, char __user *buf,
 	char *str;
 	int ret;
 
+	if (dmesg_restrict && !capable(CAP_SYSLOG))
+		return -EPERM;
+
 	/* Main last_kmsg log */
 	if (pos < old_log_size) {
 		count = min(len, (size_t)(old_log_size - pos));
-- 
1.7.3.2.146.gca209

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