[PATCH 4/4] fuse: Only allow read/writing user xattrs

[Eric W. Biederman]

In the context of unprivileged mounts supporting anything except
xattrs with the "user." prefix seems foolish.  Return -EOPNOSUPP
for all other types of xattrs.

Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
 fs/fuse/dir.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index d74c75a057cd..d84f5b819fab 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <linux/namei.h>
 #include <linux/slab.h>
+#include <linux/xattr.h>
 
 static bool fuse_use_readdirplus(struct inode *dir, struct dir_context *ctx)
 {
@@ -1868,6 +1869,9 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 	if (fc->no_setxattr)
 		return -EOPNOTSUPP;
 
+	if (strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) != 0)
+		return -EOPNOTSUPP;
+
 	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
@@ -1911,6 +1915,9 @@ static ssize_t fuse_getxattr(struct dentry *entry, const char *name,
 	if (fc->no_getxattr)
 		return -EOPNOTSUPP;
 
+	if (strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) != 0)
+		return -EOPNOTSUPP;
+
 	req = fuse_get_req_nopages(fc);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
-- 
1.9.1


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