Update dmesg_restrict patch to v2
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@ -1,46 +1,162 @@
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From feaf4959c30d0640093a607c577940d3e9351076 Mon Sep 17 00:00:00 2001
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From ce10d1b72b4da3c98bbbcb1b945687d964c31923 Mon Sep 17 00:00:00 2001
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From: Josh Boyer <jwboyer@redhat.com>
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Date: Fri, 22 Feb 2013 11:47:37 -0500
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Date: Tue, 9 Apr 2013 11:08:13 -0400
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Subject: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg
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Originally, the addition of the dmesg_restrict covered both the syslog
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method of accessing dmesg, as well as /dev/kmsg itself. This was done
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indirectly by security_syslog calling cap_syslog before doing any LSM
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checks.
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The dmesg_restrict sysctl currently covers the syslog method for access
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dmesg, however /dev/kmsg isn't covered by the same protections. Most
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people haven't noticed because util-linux dmesg(1) defaults to using the
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syslog method for access in older versions. With util-linux dmesg(1)
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defaults to reading directly from /dev/kmsg.
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However, commit 12b3052c3ee (capabilities/syslog: open code cap_syslog
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logic to fix build failure) moved the code around and pushed the checks
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into the caller itself. That seems to have inadvertently dropped the
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checks for dmesg_restrict on /dev/kmsg. Most people haven't noticed
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because util-linux dmesg(1) defaults to using the syslog method for
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access in older versions. With util-linux 2.22 and a kernel newer than
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3.5, dmesg(1) defaults to reading directly from /dev/kmsg.
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Fix this by making an explicit check in the devkmsg_open function.
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Fix this by reworking all of the access methods to use the
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check_syslog_permissions function and adding checks to devkmsg_open and
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devkmsg_read.
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This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192
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Reported-by: Christian Kujau <lists@nerdbynature.de>
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CC: stable@vger.kernel.org
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Signed-off-by: Eric Paris <eparis@redhat.com>
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Signed-off-by: Josh Boyer <jwboyer@redhat.com>
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---
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kernel/printk.c | 3 +++
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1 file changed, 3 insertions(+)
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kernel/printk.c | 91 +++++++++++++++++++++++++++++----------------------------
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1 file changed, 47 insertions(+), 44 deletions(-)
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diff --git a/kernel/printk.c b/kernel/printk.c
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index f24633a..398ef9a 100644
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index abbdd9e..5541095 100644
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--- a/kernel/printk.c
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+++ b/kernel/printk.c
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@@ -615,6 +615,9 @@ static int devkmsg_open(struct inode *inode, struct file *file)
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struct devkmsg_user *user;
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int err;
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@@ -368,6 +368,46 @@ static void log_store(int facility, int level,
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log_next_seq++;
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}
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+ if (dmesg_restrict && !capable(CAP_SYSLOG))
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+ return -EACCES;
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+#ifdef CONFIG_SECURITY_DMESG_RESTRICT
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+int dmesg_restrict = 1;
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+#else
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+int dmesg_restrict;
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+#endif
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+
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/* write-only does not need any file context */
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+static int syslog_action_restricted(int type)
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+{
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+ if (dmesg_restrict)
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+ return 1;
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+ /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
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+ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
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+}
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+
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+static int check_syslog_permissions(int type, bool from_file)
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+{
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+ /*
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+ * If this is from /proc/kmsg and we've already opened it, then we've
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+ * already done the capabilities checks at open time.
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+ */
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+ if (from_file && type != SYSLOG_ACTION_OPEN)
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+ goto ok;
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+
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+ if (syslog_action_restricted(type)) {
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+ if (capable(CAP_SYSLOG))
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+ goto ok;
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+ /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
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+ if (capable(CAP_SYS_ADMIN)) {
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+ printk_once(KERN_WARNING "%s (%d): "
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+ "Attempt to access syslog with CAP_SYS_ADMIN "
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+ "but no CAP_SYSLOG (deprecated).\n",
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+ current->comm, task_pid_nr(current));
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+ goto ok;
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+ }
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+ return -EPERM;
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+ }
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+ok:
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+ return security_syslog(type);
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+}
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+
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/* /dev/kmsg - userspace message inject/listen interface */
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struct devkmsg_user {
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u64 seq;
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@@ -443,10 +483,16 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
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char cont = '-';
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size_t len;
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ssize_t ret;
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+ int err;
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if (!user)
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return -EBADF;
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+ err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
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+ SYSLOG_FROM_FILE);
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+ if (err)
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+ return err;
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+
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ret = mutex_lock_interruptible(&user->lock);
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if (ret)
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return ret;
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@@ -624,7 +670,7 @@ static int devkmsg_open(struct inode *inode, struct file *file)
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if ((file->f_flags & O_ACCMODE) == O_WRONLY)
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return 0;
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- err = security_syslog(SYSLOG_ACTION_READ_ALL);
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+ err = check_syslog_permissions(SYSLOG_ACTION_OPEN, SYSLOG_FROM_FILE);
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if (err)
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return err;
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@@ -817,45 +863,6 @@ static inline void boot_delay_msec(int level)
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}
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#endif
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-#ifdef CONFIG_SECURITY_DMESG_RESTRICT
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-int dmesg_restrict = 1;
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-#else
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-int dmesg_restrict;
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-#endif
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-
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-static int syslog_action_restricted(int type)
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-{
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- if (dmesg_restrict)
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- return 1;
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- /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
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- return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
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-}
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-
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-static int check_syslog_permissions(int type, bool from_file)
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-{
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- /*
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- * If this is from /proc/kmsg and we've already opened it, then we've
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- * already done the capabilities checks at open time.
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- */
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- if (from_file && type != SYSLOG_ACTION_OPEN)
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- return 0;
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-
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- if (syslog_action_restricted(type)) {
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- if (capable(CAP_SYSLOG))
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- return 0;
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- /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
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- if (capable(CAP_SYS_ADMIN)) {
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- printk_once(KERN_WARNING "%s (%d): "
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- "Attempt to access syslog with CAP_SYS_ADMIN "
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- "but no CAP_SYSLOG (deprecated).\n",
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- current->comm, task_pid_nr(current));
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- return 0;
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- }
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- return -EPERM;
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- }
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- return 0;
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-}
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-
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#if defined(CONFIG_PRINTK_TIME)
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static bool printk_time = 1;
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#else
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@@ -1131,10 +1138,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
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if (error)
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goto out;
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- error = security_syslog(type);
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- if (error)
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- return error;
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-
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switch (type) {
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case SYSLOG_ACTION_CLOSE: /* Close log */
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break;
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--
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1.8.1.2
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1.8.1.4
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