linux-kernel - [PATCH 07/26] ubifs: Massage ubifs_listxattr() for encryption context

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Date:   Fri, 21 Oct 2016 14:48:22 +0200
From:   Richard Weinberger <richard@....at>
To:     linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        dedekind1@...il.com, adrian.hunter@...el.com, tytso@....edu,
        jaegeuk@...nel.org, david@...ma-star.at, wd@...x.de,
        sbabic@...x.de, dengler@...utronix.de,
        Richard Weinberger <richard@....at>
Subject: [PATCH 07/26] ubifs: Massage ubifs_listxattr() for encryption context

We have to make sure that we don't expose our internal
crypto context to userspace.

Signed-off-by: Richard Weinberger <richard@....at>
---
 fs/ubifs/xattr.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index b390902c48aa..54ec2b9fd506 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -394,6 +394,20 @@ out_unlock:
 	return err;
 }
 
+static bool xattr_visible(const char *name)
+{
+	/* File encryption related xattrs are for internal use only */
+	if (strcmp(name, UBIFS_XATTR_NAME_ENCRYPTION_CONTEXT) == 0)
+		return false;
+
+	/* Show trusted namespace only for "power" users */
+	if (strncmp(name, XATTR_TRUSTED_PREFIX,
+		    XATTR_TRUSTED_PREFIX_LEN) == 0 && !capable(CAP_SYS_ADMIN))
+		return false;
+
+	return true;
+}
+
 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
 	union ubifs_key key;
@@ -429,10 +443,7 @@ ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 		nm.name = xent->name;
 		nm.len = le16_to_cpu(xent->nlen);
 
-		/* Show trusted namespace only for "power" users */
-		if (strncmp(xent->name, XATTR_TRUSTED_PREFIX,
-			    XATTR_TRUSTED_PREFIX_LEN) ||
-		    capable(CAP_SYS_ADMIN)) {
+		if (xattr_visible(xent->name)) {
 			memcpy(buffer + written, nm.name, nm.len + 1);
 			written += nm.len + 1;
 		}
-- 
2.7.3