[PATCH 2/2] mm: restrict access to /proc/meminfo

[Vasiliy Kulikov <segoon@openwall.com>]

/proc/meminfo stores information related to memory pages usage, which
may be used to monitor the number of objects in specific caches (and/or
the changes of these numbers).  This might reveal private information
similar to /proc/slabinfo infoleaks.  To remove the infoleak, just
restrict meminfo to root.  If it is used by unprivileged daemons,
meminfo permissions can be altered the same way as slabinfo:

    groupadd meminfo
    usermod -a -G meminfo $MONITOR_USER
    chmod g+r /proc/meminfo
    chgrp meminfo /proc/meminfo

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
CC: Kees Cook <kees@ubuntu.com>
CC: Dave Hansen <dave@linux.vnet.ibm.com>
CC: Christoph Lameter <cl@gentwo.org>
CC: Pekka Enberg <penberg@cs.helsinki.fi>
CC: Valdis.Kletnieks@vt.edu
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: David Rientjes <rientjes@google.com>
CC: Alan Cox <alan@linux.intel.com>
---
 fs/proc/meminfo.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

--
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 5861741..949bdee 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -187,7 +187,7 @@ static const struct file_operations meminfo_proc_fops = {
 
 static int __init proc_meminfo_init(void)
 {
-	proc_create("meminfo", 0, NULL, &meminfo_proc_fops);
+	proc_create("meminfo", S_IFREG | S_IRUSR, NULL, &meminfo_proc_fops);
 	return 0;
 }
 module_init(proc_meminfo_init);

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