On Sat, Dec 19, 2020 at 11:07 AM Amir Goldstein amir73il@gmail.com wrote:
When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will intercept in inode_getxattr hooks.
When selinux LSM is installed but not initialized, it will list the security.selinux xattr in inode_listsecurity, but will not intercept it in inode_getxattr. This results in -ENODATA for a getxattr call for an xattr returned by listxattr.
This situation was manifested as overlayfs failure to copy up lower files from squashfs when selinux is built-in but not initialized, because ovl_copy_xattr() iterates the lower inode xattrs by vfs_listxattr() and vfs_getxattr().
Match the logic of inode_listsecurity to that of inode_getxattr and do not list the security.selinux xattr if selinux is not initialized.
Reported-by: Michael Labriola michael.d.labriola@gmail.com Tested-by: Michael Labriola michael.d.labriola@gmail.com Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.o... Fixes: c8e222616c7e ("selinux: allow reading labels before policy is loaded") Cc: stable@vger.kernel.org#v5.9+ Signed-off-by: Amir Goldstein amir73il@gmail.com
security/selinux/hooks.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 6b1826fc3658..e132e082a5af 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3406,6 +3406,10 @@ static int selinux_inode_setsecurity(struct inode *inode, const char *name, static int selinux_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) { const int len = sizeof(XATTR_NAME_SELINUX);
if (!selinux_initialized(&selinux_state))return 0;if (buffer && len <= buffer_size) memcpy(buffer, XATTR_NAME_SELINUX, len); return len;-- 2.25.1
Looked at the logic in vfs_listxattr() and this looks reasonable.
Reviewed-by: Ondrej Mosnacek omosnace@redhat.com
Thank you for the patch!