Honor dmesg_restrict for /dev/kmsg (rhbz 903192)

1 files changed, 46 insertions, 0 deletions

diff --git a/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch b/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch
new file mode 100644
index 000000000..acaf5f881
--- /dev/null
+++ b/0001-kmsg-Honor-dmesg_restrict-sysctl-on-dev-kmsg.patch
@@ -0,0 +1,46 @@
+From feaf4959c30d0640093a607c577940d3e9351076 Mon Sep 17 00:00:00 2001
+From: Josh Boyer <jwboyer@redhat.com>
+Date: Fri, 22 Feb 2013 11:47:37 -0500
+Subject: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg
+
+Originally, the addition of the dmesg_restrict covered both the syslog
+method of accessing dmesg, as well as /dev/kmsg itself.  This was done
+indirectly by security_syslog calling cap_syslog before doing any LSM
+checks.
+
+However, commit 12b3052c3ee (capabilities/syslog: open code cap_syslog
+logic to fix build failure) moved the code around and pushed the checks
+into the caller itself.  That seems to have inadvertently dropped the
+checks for dmesg_restrict on /dev/kmsg.  Most people haven't noticed
+because util-linux dmesg(1) defaults to using the syslog method for
+access in older versions.  With util-linux 2.22 and a kernel newer than
+3.5, dmesg(1) defaults to reading directly from /dev/kmsg.
+
+Fix this by making an explicit check in the devkmsg_open function.
+
+This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192
+
+Reported-by: Christian Kujau <lists@nerdbynature.de>
+CC: stable@vger.kernel.org
+Signed-off-by: Josh Boyer <jwboyer@redhat.com>
+---
+ kernel/printk.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/kernel/printk.c b/kernel/printk.c
+index f24633a..398ef9a 100644
+--- a/kernel/printk.c
++++ b/kernel/printk.c
+@@ -615,6 +615,9 @@ static int devkmsg_open(struct inode *inode, struct file *file)
+ 	struct devkmsg_user *user;
+ 	int err;
+ 
++	if (dmesg_restrict && !capable(CAP_SYSLOG))
++		return -EACCES;
++
+ 	/* write-only does not need any file context */
+ 	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
+ 		return 0;
+-- 
+1.8.1.2
+