pstore: Honor dmesg_restrict sysctl on dmesg dumps

When the kernel.dmesg_restrict restriction is in place, only users with
CAP_SYSLOG should be able to access crash dumps (like: attacker is
trying to exploit a bug, watchdog reboots, attacker can happily read
crash dumps and logs).

This puts the restriction on console-* types as well as sensitive
information could have been leaked there.

Other log types are unaffected.

Signed-off-by: Sebastian Schmidt <yath@yath.de>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index fafb7a02a5d6c659299ffdd92326a2345d1b3c62..50416602774d896f2523ee05e49bb2a1c647e1ce 100644 (file)
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -36,6 +36,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/uaccess.h>
+#include <linux/syslog.h>
 
 #include "internal.h"
 
@@ -120,6 +121,18 @@ static const struct seq_operations pstore_ftrace_seq_ops = {
        .show   = pstore_ftrace_seq_show,
 };
 
+static int pstore_check_syslog_permissions(struct pstore_private *ps)
+{
+       switch (ps->type) {
+       case PSTORE_TYPE_DMESG:
+       case PSTORE_TYPE_CONSOLE:
+               return check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
+                       SYSLOG_FROM_READER);
+       default:
+               return 0;
+       }
+}
+
 static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
                                                size_t count, loff_t *ppos)
 {
@@ -138,6 +151,10 @@ static int pstore_file_open(struct inode *inode, struct file *file)
        int err;
        const struct seq_operations *sops = NULL;
 
+       err = pstore_check_syslog_permissions(ps);
+       if (err)
+               return err;
+
        if (ps->type == PSTORE_TYPE_FTRACE)
                sops = &pstore_ftrace_seq_ops;
 
@@ -174,6 +191,11 @@ static const struct file_operations pstore_file_operations = {
 static int pstore_unlink(struct inode *dir, struct dentry *dentry)
 {
        struct pstore_private *p = dentry->d_inode->i_private;
+       int err;
+
+       err = pstore_check_syslog_permissions(p);
+       if (err)
+               return err;
 
        if (p->psi->erase)
                p->psi->erase(p->type, p->id, p->count,

diff --git a/include/linux/syslog.h b/include/linux/syslog.h
index 98a3153c0f964e9e5a2d9402d15e9fa8788e2d57..9def5297dbb72fb4b96dce54ce581b65363c948b 100644 (file)
--- a/include/linux/syslog.h
+++ b/include/linux/syslog.h
@@ -48,5 +48,6 @@
 #define SYSLOG_FROM_PROC             1
 
 int do_syslog(int type, char __user *buf, int count, bool from_file);
+int check_syslog_permissions(int type, bool from_file);
 
 #endif /* _LINUX_SYSLOG_H */

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ced2b84b1cb7b4f0c11e0c3d9a09bc83b1b435f0..c8755e7e1dba2f8464f7bbc2a7958a554ac611d5 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -480,7 +480,7 @@ static int syslog_action_restricted(int type)
               type != SYSLOG_ACTION_SIZE_BUFFER;
 }
 
-static int check_syslog_permissions(int type, bool from_file)
+int check_syslog_permissions(int type, bool from_file)
 {
        /*
         * If this is from /proc/kmsg and we've already opened it, then we've