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Received: from linux.microsoft.com ([13.77.154.182]) by casper.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tlaEO-0000000F70K-2Tgg for kexec@lists.infradead.org; Fri, 21 Feb 2025 21:06:49 +0000 Received: from [10.17.64.59] (unknown [131.107.8.59]) by linux.microsoft.com (Postfix) with ESMTPSA id E71A0205367B; Fri, 21 Feb 2025 13:06:38 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com E71A0205367B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1740171999; bh=FUlp7EisKMHoz+xilvHRinAU2TQZ+x4bdo9N281fpHY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=WeswjTuNzlG4W7eElUmgmU2MU266rObyW3PfV6HWjdXePbZxpzFDg8EiYGFrOooe5 vuf/vXW9Ail2ZrGQXDQnlcXLJGMjzb3XCnLtB4jBljRm+aVg4EXQOxcOR8DNiyEEGy 1+NvYn0GNnuKEqXZY41l+Z4rocZqtw5AooSP98Ps= Message-ID: Date: Fri, 21 Feb 2025 13:06:37 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 3/7] ima: kexec: skip IMA segment validation after kexec soft reboot To: Mimi Zohar , stefanb@linux.ibm.com, roberto.sassu@huaweicloud.com, roberto.sassu@huawei.com, eric.snowberg@oracle.com, ebiederm@xmission.com, paul@paul-moore.com, code@tyhicks.com, bauermann@kolabnow.com, linux-integrity@vger.kernel.org, kexec@lists.infradead.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Cc: madvenka@linux.microsoft.com, nramas@linux.microsoft.com, James.Bottomley@HansenPartnership.com, bhe@redhat.com, vgoyal@redhat.com, dyoung@redhat.com References: <20250218225502.747963-1-chenste@linux.microsoft.com> <20250218225502.747963-4-chenste@linux.microsoft.com> <1883119129dbeeabad1f5239f042a7b920feef0f.camel@linux.ibm.com> Content-Language: en-US From: steven chen In-Reply-To: <1883119129dbeeabad1f5239f042a7b920feef0f.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250221_210644_995600_CD383B75 X-CRM114-Status: GOOD ( 19.59 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 2/21/2025 7:41 AM, Mimi Zohar wrote: > On Tue, 2025-02-18 at 14:54 -0800, steven chen wrote: >> kexec_calculate_store_digests() calculates and stores the digest of the >> segment at kexec_file_load syscall where the IMA segment is also >> allocated.  With this series, the IMA segment will be updated with the >> measurement log at kexec execute stage when soft reboot is initiated. >> Therefore, it may fail digest verification in verify_sha256_digest() >> after kexec soft reboot into the new kernel. Therefore, the digest >> calculation/verification of the IMA segment needs to be skipped. >> >> Skip the calculating and storing digest of the IMA segment in >> kexec_calculate_store_digests() so that it is not added to the >> 'purgatory_sha_regions'. >> >> Since verify_sha256_digest() only verifies 'purgatory_sha_regions', >> no change is needed in verify_sha256_digest() in this context. >> >> With this change, the IMA segment is not included in the digest >> calculation, storage, and verification. > Basically you're saying because the hash verification will fail, don't include > the IMA buffer. What's missing is the reason for not caring whether the IMA > hash is included or not. > > I understand this is the best we can do without making some major kexec changes. > >> Signed-off-by: Tushar Sugandhi >> Signed-off-by: steven chen >> Reviewed-by: Stefan Berger > After updating the patch description, > > Reviewed-by: Mimi Zohar > >> --- >>  include/linux/kexec.h              |  3 +++ >>  kernel/kexec_file.c                | 22 ++++++++++++++++++++++ >>  security/integrity/ima/ima_kexec.c |  3 +++ >>  3 files changed, 28 insertions(+) >> >> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >> index 4dbf806bccef..bd554ced9fb2 100644 >> --- a/include/linux/kexec.h >> +++ b/include/linux/kexec.h >> @@ -362,6 +362,9 @@ struct kimage { >> >>   phys_addr_t ima_buffer_addr; >>   size_t ima_buffer_size; >> + >> + unsigned long ima_segment_index; >> + bool is_ima_segment_index_set; >>  #endif >> >>   /* Core ELF header buffer */ >> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c >> index 3eedb8c226ad..606132253c79 100644 >> --- a/kernel/kexec_file.c >> +++ b/kernel/kexec_file.c >> @@ -38,6 +38,21 @@ void set_kexec_sig_enforced(void) >>  } >>  #endif >> >> +#ifdef CONFIG_IMA_KEXEC >> +static bool check_ima_segment_index(struct kimage *image, int i) >> +{ >> + if (image->is_ima_segment_index_set && i == image->ima_segment_index) >> + return true; >> + else >> + return false; >> +} >> +#else >> +static bool check_ima_segment_index(struct kimage *image, int i) >> +{ >> + return false; >> +} >> +#endif >> + >>  static int kexec_calculate_store_digests(struct kimage *image); >> >>  /* Maximum size in bytes for kernel/initrd files. */ >> @@ -764,6 +779,13 @@ static int kexec_calculate_store_digests(struct kimage >> *image) >>   if (ksegment->kbuf == pi->purgatory_buf) >>   continue; >> >> + /* >> + * Skip the segment if ima_segment_index is set and matches >> + * the current index >> + */ >> + if (check_ima_segment_index(image, i)) >> + continue; >> + >>   ret = crypto_shash_update(desc, ksegment->kbuf, >>     ksegment->bufsz); >>   if (ret) >> diff --git a/security/integrity/ima/ima_kexec.c >> b/security/integrity/ima/ima_kexec.c >> index 89088f1fa989..704676fa6615 100644 >> --- a/security/integrity/ima/ima_kexec.c >> +++ b/security/integrity/ima/ima_kexec.c >> @@ -160,6 +160,7 @@ void ima_add_kexec_buffer(struct kimage *image) >>   kbuf.buffer = kexec_buffer; >>   kbuf.bufsz = kexec_buffer_size; >>   kbuf.memsz = kexec_segment_size; >> + image->is_ima_segment_index_set = false; >>   ret = kexec_add_buffer(&kbuf); >>   if (ret) { >>   pr_err("Error passing over kexec measurement buffer.\n"); >> @@ -170,6 +171,8 @@ void ima_add_kexec_buffer(struct kimage *image) >>   image->ima_buffer_addr = kbuf.mem; >>   image->ima_buffer_size = kexec_segment_size; >>   image->ima_buffer = kexec_buffer; >> + image->ima_segment_index = image->nr_segments - 1; >> + image->is_ima_segment_index_set = true; >> >>   /* >>   * kexec owns kexec_buffer after kexec_add_buffer() is called Thanks, Mimi. I will update in next version.