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ima: limit the number of open-writers integrity violations

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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>
This commit is contained in:
Mimi Zohar 2025-01-27 10:24:13 -05:00
parent 7eb172143d
commit 5b3cd80115
2 changed files with 10 additions and 2 deletions
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1
security/integrity/ima/ima.h
View File

@ -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 {

11
security/integrity/ima/ima_main.c
View File

@ -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) ||