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Fri, 12 Aug 2022 16:43:11 +0000 (GMT) From: Stefan Berger To: kexec@lists.infradead.org, devicetree@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: nayna@linux.ibm.com, nasastry@in.ibm.com, mpe@ellerman.id.au, Vaibhav Jain , Frank Rowand , Prakhar Srivastava , Lakshmi Ramasubramanian , Thiago Jung Bauermann , Rob Herring , Ritesh Harjani , Robin Murphy Subject: [PATCH v7 1/6] of: check previous kernel's ima-kexec-buffer against memory bounds Date: Fri, 12 Aug 2022 12:43:00 -0400 Message-Id: <20220812164305.2056641-2-stefanb@linux.ibm.com> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220812164305.2056641-1-stefanb@linux.ibm.com> References: <20220812164305.2056641-1-stefanb@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: PP7Srjidomn2goeqfts35Ce6ki0zJQmT X-Proofpoint-GUID: 8TwUC-nTXIAh3XwJ0_DlM6lWKMTiKwqS X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-08-12_10,2022-08-11_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 malwarescore=0 bulkscore=0 lowpriorityscore=0 spamscore=0 clxscore=1011 priorityscore=1501 mlxlogscore=999 impostorscore=0 suspectscore=0 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2208120045 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Vaibhav Jain Presently ima_get_kexec_buffer() doesn't check if the previous kernel's ima-kexec-buffer lies outside the addressable memory range. This can result in a kernel panic if the new kernel is booted with 'mem=X' arg and the ima-kexec-buffer was allocated beyond that range by the previous kernel. The panic is usually of the form below: $ sudo kexec --initrd initrd vmlinux --append='mem=16G' BUG: Unable to handle kernel data access on read at 0xc000c01fff7f0000 Faulting instruction address: 0xc000000000837974 Oops: Kernel access of bad area, sig: 11 [#1] NIP [c000000000837974] ima_restore_measurement_list+0x94/0x6c0 LR [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 Call Trace: [c00000000371fa80] [c00000000083b55c] ima_load_kexec_buffer+0xac/0x160 [c00000000371fb00] [c0000000020512c4] ima_init+0x80/0x108 [c00000000371fb70] [c0000000020514dc] init_ima+0x4c/0x120 [c00000000371fbf0] [c000000000012240] do_one_initcall+0x60/0x2c0 [c00000000371fcc0] [c000000002004ad0] kernel_init_freeable+0x344/0x3ec [c00000000371fda0] [c0000000000128a4] kernel_init+0x34/0x1b0 [c00000000371fe10] [c00000000000ce64] ret_from_kernel_thread+0x5c/0x64 Instruction dump: f92100b8 f92100c0 90e10090 910100a0 4182050c 282a0017 3bc00000 40810330 7c0802a6 fb610198 7c9b2378 f80101d0 2c090001 40820614 e9240010 ---[ end trace 0000000000000000 ]--- Fix this issue by checking returned PFN range of previous kernel's ima-kexec-buffer with page_is_ram() to ensure correct memory bounds. Fixes: 467d27824920 ("powerpc: ima: get the kexec buffer passed by the previous kernel") Cc: Frank Rowand Cc: Prakhar Srivastava Cc: Lakshmi Ramasubramanian Cc: Thiago Jung Bauermann Cc: Rob Herring Cc: Ritesh Harjani Cc: Robin Murphy Signed-off-by: Vaibhav Jain Signed-off-by: Rob Herring Link: https://lore.kernel.org/r/20220531041446.3334259-1-vaibhav@linux.ibm.com --- drivers/of/kexec.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c index 8d374cc552be..91b04b04eec4 100644 --- a/drivers/of/kexec.c +++ b/drivers/of/kexec.c @@ -126,6 +126,7 @@ int ima_get_kexec_buffer(void **addr, size_t *size) { int ret, len; unsigned long tmp_addr; + unsigned long start_pfn, end_pfn; size_t tmp_size; const void *prop; @@ -140,6 +141,22 @@ int ima_get_kexec_buffer(void **addr, size_t *size) if (ret) return ret; + /* Do some sanity on the returned size for the ima-kexec buffer */ + if (!tmp_size) + return -ENOENT; + + /* + * Calculate the PFNs for the buffer and ensure + * they are with in addressable memory. + */ + start_pfn = PHYS_PFN(tmp_addr); + end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1); + if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn)) { + pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n", + tmp_addr, tmp_size); + return -EINVAL; + } + *addr = __va(tmp_addr); *size = tmp_size;