ima: limit the number of open-writers integrity violations

Each time a file in policy, that is already opened for write, is opened
for read, an open-writers integrity violation audit message is emitted
and a violation record is added to the IMA measurement list. This
occurs even if an open-writers violation has already been recorded.

Limit the number of open-writers integrity violations for an existing
file open for write to one.  After the existing file open for write
closes (__fput), subsequent open-writers integrity violations may be
emitted.

Cc: stable@vger.kernel.org # applies cleanly up to linux-6.6
Tested-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Tested-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index a4f284bd846c154f1b1627456e1b8faa31eb30a3..3423b3088de5080c5b49935037021bd5da3d1ccb 100644 (file)
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -182,6 +182,7 @@ struct ima_kexec_hdr {
 #define IMA_CHANGE_ATTR                2
 #define IMA_DIGSIG             3
 #define IMA_MUST_MEASURE       4
+#define IMA_EMITTED_OPENWRITERS        5
 
 /* IMA integrity metadata associated with an inode */
 struct ima_iint_cache {

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 28b8b0db6f9bbc502b4703dc336225a87fc266c4..95118c1887cb69c2c4650d086df24088b25cfa3e 100644 (file)
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -137,8 +137,13 @@ static void ima_rdwr_violation_check(struct file *file,
        } else {
                if (must_measure)
                        set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
-               if (inode_is_open_for_write(inode) && must_measure)
-                       send_writers = true;
+
+               /* Limit number of open_writers violations */
+               if (inode_is_open_for_write(inode) && must_measure) {
+                       if (!test_and_set_bit(IMA_EMITTED_OPENWRITERS,
+                                             &iint->atomic_flags))
+                               send_writers = true;
+               }
        }
 
        if (!send_tomtou && !send_writers)
@@ -167,6 +172,8 @@ static void ima_check_last_writer(struct ima_iint_cache *iint,
        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) ||