On Fri, May 20, 2016 at 11:53:18PM +0300, Krisztian Litkey wrote: > On Fri, May 20, 2016 at 8:00 PM, Mimi Zohar <[email protected]> wrote:
> > We deferred __fput() back in 2012 in order for IMA to safely take the > > i_mutex and write security.ima. Writing the security.ima xattr now > > triggers overlayfs to write the xattr, but overlayfs doesn't > > differentiate between callers - as a result of userspace or as described > > here in __fput(). All calls to ovl_setxattr() should call vfs_sexattr, > > except the one triggered by __fput(). Refer to the original lockdep > > report - > > http://thread.gmane.org/gmane.linux.file-systems.union/640 Looks like more fallout from 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay"). Not sure what we want here. Doing everything on the underlying dentry/inode would be trivial (see attached patch). Question is, can we get setxattr() on file opened for O_RDONLY? If so, then that could fail on overlayfs (lower layer is read-only). Thanks, Miklos --- From: Miklos Szeredi <[email protected]> Subject: ima: use file_path() Ima tries to call ->setxattr() on overlayfs dentry after having locked underlying inode, which results in a deadlock. Reported-by: Krisztian Litkey <[email protected]> Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay") Signed-off-by: Miklos Szeredi <[email protected]> Cc: <[email protected]> # v4.2 --- security/integrity/ima/ima_appraise.c | 4 ++-- security/integrity/ima/ima_main.c | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -222,7 +222,7 @@ static int process_measurement(struct fi if ((action & IMA_APPRAISE_SUBMASK) || strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) /* read 'security.ima' */ - xattr_len = ima_read_xattr(file->f_path.dentry, &xattr_value); + xattr_len = ima_read_xattr(file_dentry(file), &xattr_value); hash_algo = ima_get_hash_algo(xattr_value, xattr_len); --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -190,7 +190,7 @@ int ima_appraise_measurement(enum ima_ho { static const char op[] = "appraise_data"; char *cause = "unknown"; - struct dentry *dentry = file->f_path.dentry; + struct dentry *dentry = file_dentry(file); struct inode *inode = d_backing_inode(dentry); enum integrity_status status = INTEGRITY_UNKNOWN; int rc = xattr_len, hash_start = 0; @@ -295,7 +295,7 @@ int ima_appraise_measurement(enum ima_ho */ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) { - struct dentry *dentry = file->f_path.dentry; + struct dentry *dentry = file_dentry(file); int rc = 0; /* do not collect and update hash for digital signatures */
