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R. Silva" To: Mimi Zohar , Dmitry Kasatkin , Paul Moore , James Morris , "Serge E. Hallyn" Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org Subject: [PATCH] ima: Add __counted_by for struct modsig and use struct_size() Message-ID: MIME-Version: 1.0 Content-Disposition: inline X-Spam-Status: No, score=2.4 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, RCVD_IN_SBL_CSS,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on howler.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Mon, 09 Oct 2023 12:53:08 -0700 (PDT) X-Spam-Level: ** X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1779308892045770542 X-GMAIL-MSGID: 1779308892045770542 Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions). Also, relocate `hdr->raw_pkcs7_len = sig_len;` so that the __counted_by annotation has effect, and flex-array member `raw_pkcs7` can be properly bounds-checked at run-time. While there, use struct_size() helper, instead of the open-coded version, to calculate the size for the allocation of the whole flexible structure, including of course, the flexible-array member. This code was found with the help of Coccinelle, and audited and fixed manually. Signed-off-by: Gustavo A. R. Silva Reviewed-by: Kees Cook Reviewed-by: Mimi Zohar --- security/integrity/ima/ima_modsig.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/security/integrity/ima/ima_modsig.c b/security/integrity/ima/ima_modsig.c index 3e7bee30080f..3265d744d5ce 100644 --- a/security/integrity/ima/ima_modsig.c +++ b/security/integrity/ima/ima_modsig.c @@ -29,7 +29,7 @@ struct modsig { * storing the signature. */ int raw_pkcs7_len; - u8 raw_pkcs7[]; + u8 raw_pkcs7[] __counted_by(raw_pkcs7_len); }; /* @@ -65,10 +65,11 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, buf_len -= sig_len + sizeof(*sig); /* Allocate sig_len additional bytes to hold the raw PKCS#7 data. */ - hdr = kzalloc(sizeof(*hdr) + sig_len, GFP_KERNEL); + hdr = kzalloc(struct_size(hdr, raw_pkcs7, sig_len), GFP_KERNEL); if (!hdr) return -ENOMEM; + hdr->raw_pkcs7_len = sig_len; hdr->pkcs7_msg = pkcs7_parse_message(buf + buf_len, sig_len); if (IS_ERR(hdr->pkcs7_msg)) { rc = PTR_ERR(hdr->pkcs7_msg); @@ -77,7 +78,6 @@ int ima_read_modsig(enum ima_hooks func, const void *buf, loff_t buf_len, } memcpy(hdr->raw_pkcs7, buf + buf_len, sig_len); - hdr->raw_pkcs7_len = sig_len; /* We don't know the hash algorithm yet. */ hdr->hash_algo = HASH_ALGO__LAST;