From 67d8e04e345eafcb2940066f435815032eec467d Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 3 Nov 2015 12:40:59 +1100 Subject: [PATCH] xfs: invalidate cached acl if set directly via xattr ACLs are stored as extended attributes of the inode to which they apply. XFS converts the standard "system.posix_acl_[access|default]" attribute names used to control ACLs to "trusted.SGI_ACL_[FILE|DEFAULT]" as stored on-disk. These xattrs are directly exposed in on-disk format via getxattr/setxattr, without any ACL aware code in the path to perform validation, etc. This is partly historical and supports backup/restore applications such as xfsdump to back up and restore the binary blob that represents ACLs as-is. Andreas reports that the ACLs observed via the getfacl interface is not consistent when ACLs are set directly via the setxattr path. This occurs because the ACLs are cached in-core against the inode and the xattr path has no knowledge that the operation relates to ACLs. Update the xattr set codepath to trap writes of the special XFS ACL attributes and invalidate the associated cached ACL when this occurs. This ensures that the correct ACLs are used on a subsequent operation through the actual ACL interface. Note that this does not update or add support for setting the ACL xattrs directly beyond the restore use case that requires a correctly formatted binary blob and to restore a consistent i_mode at the same time. It is still possible for a root user to set an invalid or inconsistent (with i_mode) ACL blob on-disk and potentially cause corruption. [ With fixes from Andreas Gruenbacher. ] Reported-by: Andreas Gruenbacher Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- fs/xfs/xfs_xattr.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c index c036815183cb..1e08d3e85cd0 100644 --- a/fs/xfs/xfs_xattr.c +++ b/fs/xfs/xfs_xattr.c @@ -57,7 +57,8 @@ static int xfs_xattr_set(struct dentry *dentry, const char *name, const void *value, size_t size, int flags, int xflags) { - struct xfs_inode *ip = XFS_I(d_inode(dentry)); + struct xfs_inode *ip = XFS_I(d_inode(dentry)); + int error; if (strcmp(name, "") == 0) return -EINVAL; @@ -70,8 +71,24 @@ xfs_xattr_set(struct dentry *dentry, const char *name, const void *value, if (!value) return xfs_attr_remove(ip, (unsigned char *)name, xflags); - return xfs_attr_set(ip, (unsigned char *)name, + error = xfs_attr_set(ip, (unsigned char *)name, (void *)value, size, xflags); + /* + * Invalidate any cached ACLs if the user has bypassed the ACL + * interface. We don't validate the content whatsoever so it is caller + * responsibility to provide data in valid format and ensure i_mode is + * consistent. + */ +#ifdef CONFIG_XFS_POSIX_ACL + if (!error && (xflags & ATTR_ROOT)) { + if (!strcmp(name, SGI_ACL_FILE)) + forget_cached_acl(VFS_I(ip), ACL_TYPE_ACCESS); + else if (!strcmp(name, SGI_ACL_DEFAULT)) + forget_cached_acl(VFS_I(ip), ACL_TYPE_DEFAULT); + } +#endif + + return error; } static const struct xattr_handler xfs_xattr_user_handler = { -- GitLab