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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Christian Brauner <brauner@kernel.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 136/530] ima: fix blocking of security.ima xattrs of unsupported algorithms
Date:   Mon, 24 Oct 2022 13:28:00 +0200
Message-Id: <20221024113051.209158341@linuxfoundation.org>
In-Reply-To: <20221024113044.976326639@linuxfoundation.org>
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From: Mimi Zohar <zohar@linux.ibm.com>

[ Upstream commit 5926586f291b53cb8a0c9631fc19489be1186e2d ]

Limit validating the hash algorithm to just security.ima xattr, not
the security.evm xattr or any of the protected EVM security xattrs,
nor posix acls.

Fixes: 50f742dd9147 ("IMA: block writes of the security.ima xattr with unsupported algorithms")
Reported-by: Christian Brauner <brauner@kernel.org>
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 security/integrity/ima/ima_appraise.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index ed04bb7c7512..08b49bd1e8ca 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -644,22 +644,26 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 	const struct evm_ima_xattr_data *xvalue = xattr_value;
 	int digsig = 0;
 	int result;
+	int err;
 
 	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
 				   xattr_value_len);
 	if (result == 1) {
 		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
 			return -EINVAL;
+
+		err = validate_hash_algo(dentry, xvalue, xattr_value_len);
+		if (err)
+			return err;
+
 		digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
 	} else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) {
 		digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG);
 	}
 	if (result == 1 || evm_revalidate_status(xattr_name)) {
-		result = validate_hash_algo(dentry, xvalue, xattr_value_len);
-		if (result)
-			return result;
-
 		ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
+		if (result == 1)
+			result = 0;
 	}
 	return result;
 }
-- 
2.35.1