Patch "fs/xattr.c: zero out memory copied to userspace in getxattr" has been added to the 4.11-stable tree

Patch "fs/xattr.c: zero out memory copied to userspace in getxattr" has been added to the 4.11-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    fs/xattr.c: zero out memory copied to userspace in getxattr

to the 4.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-xattr.c-zero-out-memory-copied-to-userspace-in-getxattr.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 81be3dee96346fbe08c31be5ef74f03f6b63cf68 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Mon, 8 May 2017 15:57:24 -0700
Subject: fs/xattr.c: zero out memory copied to userspace in getxattr

From: Michal Hocko <mhocko@suse.com>

commit 81be3dee96346fbe08c31be5ef74f03f6b63cf68 upstream.

getxattr uses vmalloc to allocate memory if kzalloc fails.  This is
filled by vfs_getxattr and then copied to the userspace.  vmalloc,
however, doesn't zero out the memory so if the specific implementation
of the xattr handler is sloppy we can theoretically expose a kernel
memory.  There is no real sign this is really the case but let's make
sure this will not happen and use vzalloc instead.

Fixes: 779302e67835 ("fs/xattr.c:getxattr(): improve handling of allocation failures")
Link: http://lkml.kernel.org/r/20170306103327.2766-1-mhocko@kernel.org
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/xattr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -530,7 +530,7 @@ getxattr(struct dentry *d, const char __
 			size = XATTR_SIZE_MAX;
 		kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 		if (!kvalue) {
-			kvalue = vmalloc(size);
+			kvalue = vzalloc(size);
 			if (!kvalue)
 				return -ENOMEM;
 		}


Patches currently in stable-queue which might be from mhocko@suse.com are

queue-4.11/fs-xattr.c-zero-out-memory-copied-to-userspace-in-getxattr.patch
queue-4.11/mm-vmscan-fix-io-refault-regression-in-cache-workingset-transition.patch
queue-4.11/mm-prevent-potential-recursive-reclaim-due-to-clearing-pf_memalloc.patch