[PATCH 6.6 35/82] ima: fix buffer overrun in ima_eventdigest_init_common

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6.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Samasth Norway Ananda <samasth.norway.ananda@xxxxxxxxxx>

commit 923168a0631bc42fffd55087b337b1b6c54dcff5 upstream.

Function ima_eventdigest_init() calls ima_eventdigest_init_common()
with HASH_ALGO__LAST which is then used to access the array
hash_digest_size[] leading to buffer overrun. Have a conditional
statement to handle this.

Fixes: 9fab303a2cb3 ("ima: fix violation measurement list record")
Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@xxxxxxxxxx>
Tested-by: Enrico Bravi (PhD at polito.it) <enrico.bravi@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.19+
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 security/integrity/ima/ima_template_lib.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -318,15 +318,21 @@ static int ima_eventdigest_init_common(c
 				      hash_algo_name[hash_algo]);
 	}
 
-	if (digest)
+	if (digest) {
 		memcpy(buffer + offset, digest, digestsize);
-	else
+	} else {
 		/*
 		 * If digest is NULL, the event being recorded is a violation.
 		 * Make room for the digest by increasing the offset by the
-		 * hash algorithm digest size.
+		 * hash algorithm digest size. If the hash algorithm is not
+		 * specified increase the offset by IMA_DIGEST_SIZE which
+		 * fits SHA1 or MD5
 		 */
-		offset += hash_digest_size[hash_algo];
+		if (hash_algo < HASH_ALGO__LAST)
+			offset += hash_digest_size[hash_algo];
+		else
+			offset += IMA_DIGEST_SIZE;
+	}
 
 	return ima_write_template_field_data(buffer, offset + digestsize,
 					     fmt, field_data);






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