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[52.70.167.183]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6f4c08ef1a6sm8960636d6.7.2025.04.24.05.46.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Apr 2025 05:46:53 -0700 (PDT) From: Stephen Smalley To: paul@paul-moore.com Cc: omosnace@redhat.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, Stephen Smalley , Greg Kroah-Hartman , Tejun Heo , Alexander Viro , Christian Brauner , Jan Kara , Hugh Dickins , Baolin Wang , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] vfs,shmem,kernfs: fix listxattr to include security.* xattrs Date: Thu, 24 Apr 2025 08:46:43 -0400 Message-ID: <20250424124644.4413-1-stephen.smalley.work@gmail.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 $ getfattr -m.* /sys/kernel/fscaps After: $ getfattr -m.* /run/initramfs security.selinux $ getfattr -m.* /sys/kernel/fscaps security.selinux Link: https://lore.kernel.org/selinux/CAFqZXNtF8wDyQajPCdGn=3DiOawX4y77ph0E= cfcqcUUj+T87FKyA@mail.gmail.com/ Link: https://lore.kernel.org/selinux/20250423175728.3185-2-stephen.smalley= .work@gmail.com/ Signed-off-by: Stephen Smalley --- fs/kernfs/inode.c | 8 +++++++- fs/xattr.c | 13 +++++++++++++ mm/shmem.c | 8 +++++++- 3 files changed, 27 insertions(+), 2 deletions(-) diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index b83054da68b3..8fd69e48d32d 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -140,12 +140,18 @@ ssize_t kernfs_iop_listxattr(struct dentry *dentry, c= har *buf, size_t size) { struct kernfs_node *kn =3D kernfs_dentry_node(dentry); struct kernfs_iattrs *attrs; + ssize_t sz; =20 attrs =3D kernfs_iattrs(kn); if (!attrs) return -ENOMEM; =20 - return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); + sz =3D simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size); + if (sz >=3D 0 && sz <=3D size) + sz +=3D security_inode_listsecurity(d_inode(dentry), + buf ? buf + sz : NULL, + size - sz); + return sz; } =20 static inline void set_default_inode_attr(struct inode *inode, umode_t mod= e) diff --git a/fs/xattr.c b/fs/xattr.c index 02bee149ad96..68ac91d0dbc3 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -1428,6 +1428,15 @@ static bool xattr_is_trusted(const char *name) return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN); } =20 +static bool xattr_is_maclabel(const char *name) +{ + const char *suffix =3D 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 @@ -1468,6 +1477,10 @@ ssize_t simple_xattr_list(struct inode *inode, struc= t simple_xattrs *xattrs, if (!trusted && xattr_is_trusted(xattr->name)) continue; =20 + /* skip MAC labels; these are provided by LSM separately */ + if (xattr_is_maclabel(xattr->name)) + continue; + err =3D xattr_list_one(&buffer, &remaining_size, xattr->name); if (err) break; diff --git a/mm/shmem.c b/mm/shmem.c index 99327c30507c..69f664668a3a 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -4372,7 +4372,13 @@ static const struct xattr_handler * const shmem_xatt= r_handlers[] =3D { static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t= size) { struct shmem_inode_info *info =3D SHMEM_I(d_inode(dentry)); - return simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, size); + ssize_t sz =3D simple_xattr_list(d_inode(dentry), &info->xattrs, buffer, + size); + if (sz >=3D 0 && sz <=3D size) + sz +=3D security_inode_listsecurity(d_inode(dentry), + buffer ? buffer + sz : NULL, + size - sz); + return sz; } #endif /* CONFIG_TMPFS_XATTR */ =20 --=20 2.49.0