From: Roberto Sassu <roberto.sassu@xxxxxxxxxx> As sg_set_buf() requires the buffer for a crypto operation to be in the linear mapping area, so that it is always in adjacent pages, ensure that this requirement is met for IMA/EVM. Currently, evm_verify_hmac() and xattr_verify() put the evm_digest and ima_max_digest_data structures in the stack. As normally the stack is in the linear mapping area, passing them to sg_set_buf() would not be a problem. However, if CONFIG_VMAP_STACK is enabled, these structures will reside in the vmalloc area instead. If CONFIG_DEBUG_SG is enabled, the kernel will panic: [ 467.077359] kernel BUG at include/linux/scatterlist.h:163! [ 467.077939] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [...] [ 467.095225] Call Trace: [ 467.096088] <TASK> [ 467.096928] ? rcu_read_lock_held_common+0xe/0x50 [ 467.097569] ? rcu_read_lock_sched_held+0x13/0x70 [ 467.098123] ? trace_hardirqs_on+0x2c/0xd0 [ 467.098647] ? public_key_verify_signature+0x470/0x470 [ 467.099237] asymmetric_verify+0x14c/0x300 [ 467.099869] evm_verify_hmac+0x245/0x360 [ 467.100391] evm_inode_setattr+0x43/0x190 To overcome this problem, dynamically allocate the structures with kmalloc() if CONFIG_VMAP_STACK is enabled, so that they are placed in the linear mapping area, and use them instead of the in-stack counterparts. A test report is available here: https://github.com/robertosassu/ima-evm-utils/actions/runs/3590837109/jobs/6045608579 which contains the following test (include tests for EVM portable signatures and IMA verity signatures): https://github.com/robertosassu/ima-evm-utils/commit/41cf11d299e9fc2d13a60dce4b275c2675d9cc23 Changelog: v1: - Dynamically allocate the data structures in IMA and EVM, when necessary, instead of always making a copy in asymmetric_verify() (suggested by Mimi) Roberto Sassu (2): evm: Alloc evm_digest in evm_verify_hmac() if CONFIG_VMAP_STACK=y ima: Alloc ima_max_digest_data in xattr_verify() if CONFIG_VMAP_STACK=y security/integrity/evm/evm_main.c | 26 +++++++++++++++++++++----- security/integrity/ima/ima_appraise.c | 19 ++++++++++++++++--- 2 files changed, 37 insertions(+), 8 deletions(-) -- 2.25.1
