ima: fallback to using i_version to detect file change

Commit db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
replaced detecting file change based on i_version with
STATX_CHANGE_COOKIE.

On filesystems without STATX_CHANGE_COOKIE enabled, revert back to
detecting file change based on i_version.

On filesystems which do not support either, assume the file changed.

Reported-by: Frederick Lawler <fred@cloudflare.com>
Fixes: db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
Cc: stable@vger.kernel.org
Reviewed-by: Frederick Lawler <fred@cloudflare.com>
Tested-by: Frederick Lawler <fred@cloudflare.com>
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 d15becc8c640fcf63306c9c1c04e42d875d04b76..0916f24f005f2bf82bb8b57830499e07e461c8ec 100644 (file)
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -269,15 +269,20 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
                goto out;
 
        /*
-        * Detecting file change is based on i_version. On filesystems
-        * which do not support i_version, support was originally limited
-        * to an initial measurement/appraisal/audit, but was modified to
-        * assume the file changed.
+        * Detect file change based on STATX_CHANGE_COOKIE, when supported,
+        * and fallback to detecting file change based on i_version.
+        *
+        * On filesystems which did not support i_version, support was
+        * originally limited to an initial measurement/appraisal/audit,
+        * but was later modified to assume the file changed.
         */
        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;
+       else if (IS_I_VERSION(real_inode))
+               i_version = inode_peek_iversion(real_inode);
+
        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 5808b52c842644ac37ca13499e91b133cae9aaaf..5cea53fc36dffc55dc200ff3dfc37cedc38f2b6a 100644 (file)
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -180,6 +180,29 @@ static void ima_rdwr_violation_check(struct file *file,
                                  "invalid_pcr", "open_writers");
 }
 
+/*
+ * Detect file change based on STATX_CHANGE_COOKIE, when supported, and
+ * fallback to detecting file change based on i_version. On filesystems
+ * which do not support either, assume the file changed.
+ */
+static bool ima_detect_file_change(struct ima_iint_cache *iint,
+                                  struct inode *inode, struct file *file)
+{
+       struct kstat stat;
+       int result;
+
+       result = vfs_getattr_nosec(&file->f_path, &stat, STATX_CHANGE_COOKIE,
+                                  AT_STATX_SYNC_AS_STAT);
+
+       if (!result && stat.result_mask & STATX_CHANGE_COOKIE)
+               return stat.change_cookie != iint->real_inode.version;
+
+       if (IS_I_VERSION(inode))
+               return !inode_eq_iversion(inode, iint->real_inode.version);
+
+       return true;
+}
+
 static void ima_check_last_writer(struct ima_iint_cache *iint,
                                  struct inode *inode, struct file *file)
 {
@@ -191,18 +214,13 @@ static void ima_check_last_writer(struct ima_iint_cache *iint,
 
        mutex_lock(&iint->mutex);
        if (atomic_read(&inode->i_writecount) == 1) {
-               struct kstat stat;
-
                clear_bit(IMA_EMITTED_OPENWRITERS, &iint->atomic_flags);
 
                update = test_and_clear_bit(IMA_UPDATE_XATTR,
                                            &iint->atomic_flags);
-               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->real_inode.version) {
+
+               if (iint->flags & IMA_NEW_FILE ||
+                   ima_detect_file_change(iint, inode, file)) {
                        iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
                        iint->measured_pcrs = 0;
                        if (update)