Because of the overlayfs getxattr recursion, the incoming inode fails to update the selinux sid resulting in avc denials being reported against a target context of u:object_r:unlabeled:s0.
Solution is to respond to the XATTR_NOSECURITY flag in get xattr method that calls the __vfs_getxattr handler instead so that the context can be read in, rather than being denied with an -EACCES when vfs_getxattr handler is called. For the use case where access is to be blocked by the security layer. The path then would be security(dentry) -> __vfs_getxattr(dentry...XATTR_NOSECURITY) -> handler->get(dentry...XATTR_NOSECURITY) -> __vfs_getxattr(realdentry...XATTR_NOSECURITY) -> lower_handler->get(realdentry...XATTR_NOSECURITY) which would report back through the chain data and success as expected, the logging security layer at the top would have the data to determine the access permissions and report back to the logs and the caller that the target context was blocked. For selinux this would solve the cosmetic issue of the selinux log and allow audit2allow to correctly report the rule needed to address the access problem. Signed-off-by: Mark Salyzyn <[email protected]> Cc: Miklos Szeredi <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Vivek Goyal <[email protected]> Cc: Eric W. Biederman <[email protected]> Cc: Amir Goldstein <[email protected]> Cc: Randy Dunlap <[email protected]> Cc: Stephen Smalley <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: Eric Van Hensbergen <[email protected]> Cc: Latchesar Ionkov <[email protected]> Cc: Dominique Martinet <[email protected]> Cc: David Howells <[email protected]> Cc: Chris Mason <[email protected]> Cc: Josef Bacik <[email protected]> Cc: David Sterba <[email protected]> Cc: Jeff Layton <[email protected]> Cc: Sage Weil <[email protected]> Cc: Ilya Dryomov <[email protected]> Cc: Steve French <[email protected]> Cc: Tyler Hicks <[email protected]> Cc: Jan Kara <[email protected]> Cc: Theodore Ts'o <[email protected]> Cc: Andreas Dilger <[email protected]> Cc: Jaegeuk Kim <[email protected]> Cc: Chao Yu <[email protected]> Cc: Bob Peterson <[email protected]> Cc: Andreas Gruenbacher <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Richard Weinberger <[email protected]> Cc: Dave Kleikamp <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Trond Myklebust <[email protected]> Cc: Anna Schumaker <[email protected]> Cc: Mark Fasheh <[email protected]> Cc: Joel Becker <[email protected]> Cc: Joseph Qi <[email protected]> Cc: Mike Marshall <[email protected]> Cc: Martin Brandenburg <[email protected]> Cc: Alexander Viro <[email protected]> Cc: Phillip Lougher <[email protected]> Cc: Darrick J. Wong <[email protected]> Cc: [email protected] Cc: Hugh Dickins <[email protected]> Cc: David S. Miller <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Mathieu Malaterre <[email protected]> Cc: Ernesto A. Fernández <[email protected]> Cc: Vyacheslav Dubeyko <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] # 4.4, 4.9, 4.14 & 4.19 --- v13 - rebase to use __vfs_getxattr flags option. v12 - Added back to patch series as get xattr with flag option. v11 - Squashed out of patch series and replaced with per-thread flag solution. v10 - Added to patch series as __get xattr method. --- fs/overlayfs/inode.c | 5 +++-- fs/overlayfs/overlayfs.h | 2 +- fs/overlayfs/super.c | 4 ++-- 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 7663aeb85fa3..1bf11ae44313 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -363,7 +363,7 @@ int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name, } int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name, - void *value, size_t size) + void *value, size_t size, int flags) { ssize_t res; const struct cred *old_cred; @@ -371,7 +371,8 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name, ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry); old_cred = ovl_override_creds(dentry->d_sb); - res = vfs_getxattr(realdentry, name, value, size); + res = __vfs_getxattr(realdentry, d_inode(realdentry), name, + value, size, flags); revert_creds(old_cred); return res; } diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 6934bcf030f0..ab3d031c422b 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -356,7 +356,7 @@ int ovl_permission(struct inode *inode, int mask); int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name, const void *value, size_t size, int flags); int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name, - void *value, size_t size); + void *value, size_t size, int flags); ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size); struct posix_acl *ovl_get_acl(struct inode *inode, int type); int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags); diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index a7b21f2ea2dd..6f041e1fceda 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -856,7 +856,7 @@ ovl_posix_acl_xattr_get(const struct xattr_handler *handler, struct dentry *dentry, struct inode *inode, const char *name, void *buffer, size_t size, int flags) { - return ovl_xattr_get(dentry, inode, handler->name, buffer, size); + return ovl_xattr_get(dentry, inode, handler->name, buffer, size, flags); } static int __maybe_unused @@ -938,7 +938,7 @@ static int ovl_other_xattr_get(const struct xattr_handler *handler, const char *name, void *buffer, size_t size, int flags) { - return ovl_xattr_get(dentry, inode, name, buffer, size); + return ovl_xattr_get(dentry, inode, name, buffer, size, flags); } static int ovl_other_xattr_set(const struct xattr_handler *handler, -- 2.22.0.770.g0f2c4a37fd-goog _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
