Unverified Commit 8b0ba61d authored by Stephen Smalley's avatar Stephen Smalley Committed by Christian Brauner
Browse files

fs/xattr.c: fix simple_xattr_list to always include security.* xattrs 

The vfs has long had a fallback to obtain the security.* xattrs from the
LSM when the filesystem does not implement its own listxattr, but
shmem/tmpfs and kernfs later gained their own xattr handlers to support
other xattrs. Unfortunately, as a side effect, tmpfs and kernfs-based
filesystems like sysfs no longer return the synthetic security.* xattr
names via listxattr unless they are explicitly set by userspace or
initially set upon inode creation after policy load. coreutils has
recently switched from unconditionally invoking getxattr for security.*
for ls -Z via libselinux to only doing so if listxattr returns the xattr
name, breaking ls -Z of such inodes.

Before:
$ getfattr -m.* /run/initramfs
<no output>
$ getfattr -m.* /sys/kernel/fscaps
<no output>
$ setfattr -n user.foo /run/initramfs
$ getfattr -m.* /run/initramfs
user.foo

After:
$ getfattr -m.* /run/initramfs
security.selinux
$ getfattr -m.* /sys/kernel/fscaps
security.selinux
$ setfattr -n user.foo /run/initramfs
$ getfattr -m.* /run/initramfs
security.selinux
user.foo

Link: https://lore.kernel.org/selinux/CAFqZXNtF8wDyQajPCdGn=iOawX4y77ph0EcfcqcUUj+T87FKyA@mail.gmail.com/
Link: https://lore.kernel.org/selinux/20250423175728.3185-2-stephen.smalley.work@gmail.com/


Signed-off-by: default avatarStephen Smalley <stephen.smalley.work@gmail.com>
Link: https://lore.kernel.org/20250424152822.2719-1-stephen.smalley.work@gmail.com


Fixes: b09e0fa4 ("tmpfs: implement generic xattr support")
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent b4432656

fs/xattr.c

+24 −0
Original line number Diff line number Diff line
@@ -1428,6 +1428,15 @@ static bool xattr_is_trusted(const char *name) 
	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);

}



static bool xattr_is_maclabel(const char *name)

{

	const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;



	return !strncmp(name, XATTR_SECURITY_PREFIX,

			XATTR_SECURITY_PREFIX_LEN) &&

		security_ismaclabel(suffix);

}



/**

 * simple_xattr_list - list all xattr objects

 * @inode: inode from which to get the xattrs
@@ -1460,6 +1469,17 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs, 
	if (err)

		return err;



	err = security_inode_listsecurity(inode, buffer, remaining_size);

	if (err < 0)

		return err;



	if (buffer) {

		if (remaining_size < err)

			return -ERANGE;

		buffer += err;

	}

	remaining_size -= err;



	read_lock(&xattrs->lock);

	for (rbp = rb_first(&xattrs->rb_root); rbp; rbp = rb_next(rbp)) {

		xattr = rb_entry(rbp, struct simple_xattr, rb_node);
@@ -1468,6 +1488,10 @@ ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs, 
		if (!trusted && xattr_is_trusted(xattr->name))

			continue;



		/* skip MAC labels; these are provided by LSM above */

		if (xattr_is_maclabel(xattr->name))

			continue;



		err = xattr_list_one(&buffer, &remaining_size, xattr->name);

		if (err)

			break;