IMA: use vfs_getattr_nosec to get the i_version

IMA currently accesses the i_version out of the inode directly when it
does a measurement. This is fine for most simple filesystems, but can be
problematic with more complex setups (e.g. overlayfs).

Make IMA instead call vfs_getattr_nosec to get this info. This allows
the filesystem to determine whether and how to report the i_version, and
should allow IMA to work properly with a broader class of filesystems in
the future.

Reported-and-Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index d3662f4..c45902e 100644 (file)
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -13,7 +13,6 @@
 #include <linux/fs.h>
 #include <linux/xattr.h>
 #include <linux/evm.h>
-#include <linux/iversion.h>
 #include <linux/fsverity.h>
 
 #include "ima.h"
@@ -246,10 +245,11 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
        struct inode *inode = file_inode(file);
        const char *filename = file->f_path.dentry->d_name.name;
        struct ima_max_digest_data hash;
+       struct kstat stat;
        int result = 0;
        int length;
        void *tmpbuf;
-       u64 i_version;
+       u64 i_version = 0;
 
        /*
         * Always collect the modsig, because IMA might have already collected
@@ -268,7 +268,10 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
         * to an initial measurement/appraisal/audit, but was modified to
         * assume the file changed.
         */
-       i_version = inode_query_iversion(inode);
+       result = vfs_getattr_nosec(&file->f_path, &stat, STATX_CHANGE_COOKIE,
+                                  AT_STATX_SYNC_AS_STAT);
+       if (!result && (stat.result_mask & STATX_CHANGE_COOKIE))
+               i_version = stat.change_cookie;
        hash.hdr.algo = algo;
        hash.hdr.length = hash_digest_size[algo];
 

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index d66a0a3..365db0e 100644 (file)
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -24,7 +24,6 @@
 #include <linux/slab.h>
 #include <linux/xattr.h>
 #include <linux/ima.h>
-#include <linux/iversion.h>
 #include <linux/fs.h>
 
 #include "ima.h"
@@ -164,11 +163,16 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint,
 
        mutex_lock(&iint->mutex);
        if (atomic_read(&inode->i_writecount) == 1) {
+               struct kstat stat;
+
                update = test_and_clear_bit(IMA_UPDATE_XATTR,
                                            &iint->atomic_flags);
-               if (!IS_I_VERSION(inode) ||
-                   !inode_eq_iversion(inode, iint->version) ||
-                   (iint->flags & IMA_NEW_FILE)) {
+               if ((iint->flags & IMA_NEW_FILE) ||
+                   vfs_getattr_nosec(&file->f_path, &stat,
+                                     STATX_CHANGE_COOKIE,
+                                     AT_STATX_SYNC_AS_STAT) ||
+                   !(stat.result_mask & STATX_CHANGE_COOKIE) ||
+                   stat.change_cookie != iint->version) {
                        iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
                        iint->measured_pcrs = 0;
                        if (update)