linux-kernel - [PATCH 05/24] ubifs: Massage ubifs_listxattr() for encryption context

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Date:   Thu,  1 Dec 2016 22:20:52 +0100
From:   Richard Weinberger <richard@....at>
To:     linux-mtd@...ts.infradead.org
Cc:     david@...ma-star.at, tytso@....edu, dedekind1@...il.com,
        ebiggers@...gle.com, mhalcrow@...gle.com, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, hch@...radead.org,
        linux-fsdevel@...r.kernel.org, jaegeuk@...nel.org,
        dengler@...utronix.de, sbabic@...x.de, wd@...x.de,
        Richard Weinberger <richard@....at>
Subject: [PATCH 05/24] 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 95a16028bbdb..77ffc9788f45 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -397,6 +397,20 @@ ssize_t ubifs_xattr_get(struct inode *host, const char *name, void *buf,
 	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;
@@ -432,10 +446,7 @@ 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