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Commit 68c4a4f8 authored by Sebastian Schmidt's avatar Sebastian Schmidt Committed by Tony Luck
Browse files

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: default avatarSebastian Schmidt <yath@yath.de>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent a28726b4

fs/pstore/inode.c

+22 −0
Original line number Diff line number Diff line
@@ -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,

include/linux/syslog.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/printk/printk.c

+1 −1
Original line number Diff line number Diff line
@@ -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