[PATCH 3.4 161/176] pagemap: do not leak physical addresses to non-privileged userspace

[lizf]

From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit ab676b7d6fbf4b294bf198fb27ade5b0e865c7ce upstream.

As pointed by recent post[1] on exploiting DRAM physical imperfection,
/proc/PID/pagemap exposes sensitive information which can be used to do
attacks.

This disallows anybody without CAP_SYS_ADMIN to read the pagemap.

[1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html

[ Eventually we might want to do anything more finegrained, but for now
  this is the simple model.   - Linus ]

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mark Seaborn <mseaborn@xxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
[mancha: Backported to 3.10]
Signed-off-by: mancha security <mancha1@xxxxxxxx>
---
 fs/proc/task_mmu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8df7fd2..bc17933 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -985,9 +985,19 @@ out:
 	return ret;
 }
 
+static int pagemap_open(struct inode *inode, struct file *file)
+{
+	/* do not disclose physical addresses to unprivileged
+	   userspace (closes a rowhammer attack vector) */
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
 const struct file_operations proc_pagemap_operations = {
 	.llseek		= mem_lseek, /* borrow this */
 	.read		= pagemap_read,
+	.open		= pagemap_open,
 };
 #endif /* CONFIG_PROC_PAGE_MONITOR */
 
-- 
1.9.1

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