ima: limit the number of open-writers integrity violations

commit 5b3cd801155f0b34b0b95942a5b057c9b8cad33e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 1799ea6b1d584370464417f40d68dc8a7303f412..b397329d5c6e729d69d16c1c6ee464e0304b7c0b 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 b028c501949cad7bf84f7be0b82f22bc5a86c388..db256f51e7a2daf5b05bff0bb373b3c2063c1eec 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) ||