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ima: limit the number of ToMToU integrity violations

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[ Upstream commit a414016218 ]

Each time a file in policy, that is already opened for read, is opened
for write, a Time-of-Measure-Time-of-Use (ToMToU) integrity violation
audit message is emitted and a violation record is added to the IMA
measurement list.  This occurs even if a ToMToU violation has already
been recorded.

Limit the number of ToMToU integrity violations per file open for read.

Note: The IMA_MAY_EMIT_TOMTOU atomic flag must be set from the reader
side based on policy.  This may result in a per file open for read
ToMToU violation.

Since IMA_MUST_MEASURE is only used for violations, rename the atomic
IMA_MUST_MEASURE flag to IMA_MAY_EMIT_TOMTOU.

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>
[ adapted IMA flag definitions location from ima.h to integrity.h ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mimi Zohar 2025-09-08 14:01:51 -04:00 committed by Greg Kroah-Hartman
parent 905d43b8ad
commit 0214b96a6a
2 changed files with 13 additions and 6 deletions
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16
security/integrity/ima/ima_main.c
View File

@ -128,16 +128,22 @@ static void ima_rdwr_violation_check(struct file *file,
if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
if (!iint)
iint = integrity_iint_find(inode);
/* IMA_MEASURE is set from reader side */
if (iint && test_bit(IMA_MUST_MEASURE,
&iint->atomic_flags))
if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU,
&iint->atomic_flags))
send_tomtou = true;
}
} else {
if (must_measure)
set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
if (inode_is_open_for_write(inode) && must_measure)
send_writers = true;
set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags);
/* 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)

3
security/integrity/integrity.h
View File

@ -74,7 +74,8 @@
#define IMA_UPDATE_XATTR 1
#define IMA_CHANGE_ATTR 2
#define IMA_DIGSIG 3
#define IMA_MUST_MEASURE 4
#define IMA_MAY_EMIT_TOMTOU 4
#define IMA_EMITTED_OPENWRITERS 5
enum evm_ima_xattr_type {
IMA_XATTR_DIGEST = 0x01,