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pstore: Honor dmesg_restrict sysctl on dmesg dumps

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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>
This commit is contained in:
Sebastian Schmidt 2014-10-19 20:05:15 +02:00 committed by Tony Luck
parent a28726b4fb
commit 68c4a4f8ab
3 changed files with 24 additions and 1 deletions
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22
fs/pstore/inode.c
View File

@ -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,

1
include/linux/syslog.h
View File

@ -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 */

2
kernel/printk/printk.c
View File

@ -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