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Message-ID: <20251119140326.787451-1-coxu@redhat.com>
Date: Wed, 19 Nov 2025 22:03:25 +0800
From: Coiby Xu <coxu@...hat.com>
To: linux-integrity@...r.kernel.org,
Mimi Zohar <zohar@...ux.ibm.com>
Cc: Karel Srot <ksrot@...hat.com>,
Paul Moore <paul@...l-moore.com>,
Luis Chamberlain <mcgrof@...nel.org>,
Petr Pavlu <petr.pavlu@...e.com>,
Daniel Gomez <da.gomez@...nel.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
Roberto Sassu <roberto.sassu@...wei.com>,
Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
Eric Snowberg <eric.snowberg@...cle.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Fan Wu <wufan@...nel.org>,
Stephen Smalley <stephen.smalley.work@...il.com>,
Ondrej Mosnacek <omosnace@...hat.com>,
linux-kernel@...r.kernel.org (open list),
linux-modules@...r.kernel.org (open list:MODULE SUPPORT),
linux-security-module@...r.kernel.org (open list:SECURITY SUBSYSTEM),
selinux@...r.kernel.org (open list:SELINUX SECURITY MODULE)
Subject: [PATCH v4] ima: Access decompressed kernel module to verify appended signature
Currently, when in-kernel module decompression (CONFIG_MODULE_DECOMPRESS)
is enabled, IMA has no way to verify the appended module signature as it
can't decompress the module.
Define a new kernel_read_file_id enumerate READING_MODULE_COMPRESSED so
IMA can calculate the compressed kernel module data hash on
READING_MODULE_COMPRESSED and defer appraising/measuring it until on
READING_MODULE when the module has been decompressed.
Before enabling in-kernel module decompression, a kernel module in
initramfs can still be loaded with ima_policy=secure_boot. So adjust the
kernel module rule in secure_boot policy to allow either an IMA
signature OR an appended signature i.e. to use
"appraise func=MODULE_CHECK appraise_type=imasig|modsig".
Reported-by: Karel Srot <ksrot@...hat.com>
Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
Suggested-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Coiby Xu <coxu@...hat.com>
---
include/linux/kernel_read_file.h | 1 +
kernel/module/main.c | 17 ++++++++++++++---
security/integrity/ima/ima_main.c | 24 ++++++++++++++++--------
security/integrity/ima/ima_policy.c | 3 ++-
security/ipe/hooks.c | 1 +
security/selinux/hooks.c | 5 +++--
6 files changed, 37 insertions(+), 14 deletions(-)
diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
index 90451e2e12bd..d613a7b4dd35 100644
--- a/include/linux/kernel_read_file.h
+++ b/include/linux/kernel_read_file.h
@@ -14,6 +14,7 @@
id(KEXEC_INITRAMFS, kexec-initramfs) \
id(POLICY, security-policy) \
id(X509_CERTIFICATE, x509-certificate) \
+ id(MODULE_COMPRESSED, kernel-module-compressed) \
id(MAX_ID, )
#define __fid_enumify(ENUM, dummy) READING_ ## ENUM,
diff --git a/kernel/module/main.c b/kernel/module/main.c
index c66b26184936..7b3ec2fa6e7c 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3675,24 +3675,35 @@ static int idempotent_wait_for_completion(struct idempotent *u)
static int init_module_from_file(struct file *f, const char __user * uargs, int flags)
{
+ bool compressed = !!(flags & MODULE_INIT_COMPRESSED_FILE);
struct load_info info = { };
void *buf = NULL;
int len;
+ int err;
- len = kernel_read_file(f, 0, &buf, INT_MAX, NULL, READING_MODULE);
+ len = kernel_read_file(f, 0, &buf, INT_MAX, NULL,
+ compressed ? READING_MODULE_COMPRESSED :
+ READING_MODULE);
if (len < 0) {
mod_stat_inc(&failed_kreads);
return len;
}
- if (flags & MODULE_INIT_COMPRESSED_FILE) {
- int err = module_decompress(&info, buf, len);
+ if (compressed) {
+ err = module_decompress(&info, buf, len);
vfree(buf); /* compressed data is no longer needed */
if (err) {
mod_stat_inc(&failed_decompress);
mod_stat_add_long(len, &invalid_decompress_bytes);
return err;
}
+ err = security_kernel_post_read_file(f, (char *)info.hdr, info.len,
+ READING_MODULE);
+ if (err) {
+ mod_stat_inc(&failed_kreads);
+ free_copy(&info, flags);
+ return err;
+ }
} else {
info.hdr = buf;
info.len = len;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index ebaebccfbe9a..edd0fd3d77a0 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -235,7 +235,8 @@ static void ima_file_free(struct file *file)
static int process_measurement(struct file *file, const struct cred *cred,
struct lsm_prop *prop, char *buf, loff_t size,
- int mask, enum ima_hooks func)
+ int mask, enum ima_hooks func,
+ enum kernel_read_file_id read_id)
{
struct inode *real_inode, *inode = file_inode(file);
struct ima_iint_cache *iint = NULL;
@@ -406,6 +407,12 @@ static int process_measurement(struct file *file, const struct cred *cred,
if (rc != 0 && rc != -EBADF && rc != -EINVAL)
goto out_locked;
+ /* Defer measuring/appraising kernel modules to READING_MODULE */
+ if (read_id == READING_MODULE_COMPRESSED) {
+ must_appraise = 0;
+ goto out_locked;
+ }
+
if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
pathname = ima_d_path(&file->f_path, &pathbuf, filename);
@@ -486,14 +493,14 @@ static int ima_file_mmap(struct file *file, unsigned long reqprot,
if (reqprot & PROT_EXEC) {
ret = process_measurement(file, current_cred(), &prop, NULL,
- 0, MAY_EXEC, MMAP_CHECK_REQPROT);
+ 0, MAY_EXEC, MMAP_CHECK_REQPROT, 0);
if (ret)
return ret;
}
if (prot & PROT_EXEC)
return process_measurement(file, current_cred(), &prop, NULL,
- 0, MAY_EXEC, MMAP_CHECK);
+ 0, MAY_EXEC, MMAP_CHECK, 0);
return 0;
}
@@ -577,7 +584,7 @@ static int ima_bprm_check(struct linux_binprm *bprm)
security_current_getlsmprop_subj(&prop);
return process_measurement(bprm->file, current_cred(),
- &prop, NULL, 0, MAY_EXEC, BPRM_CHECK);
+ &prop, NULL, 0, MAY_EXEC, BPRM_CHECK, 0);
}
/**
@@ -607,7 +614,7 @@ static int ima_creds_check(struct linux_binprm *bprm, const struct file *file)
security_current_getlsmprop_subj(&prop);
return process_measurement((struct file *)file, bprm->cred, &prop, NULL,
- 0, MAY_EXEC, CREDS_CHECK);
+ 0, MAY_EXEC, CREDS_CHECK, 0);
}
/**
@@ -655,7 +662,7 @@ static int ima_file_check(struct file *file, int mask)
security_current_getlsmprop_subj(&prop);
return process_measurement(file, current_cred(), &prop, NULL, 0,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
- MAY_APPEND), FILE_CHECK);
+ MAY_APPEND), FILE_CHECK, 0);
}
static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
@@ -874,12 +881,13 @@ static int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
func = read_idmap[read_id] ?: FILE_CHECK;
security_current_getlsmprop_subj(&prop);
return process_measurement(file, current_cred(), &prop, NULL, 0,
- MAY_READ, func);
+ MAY_READ, func, 0);
}
const int read_idmap[READING_MAX_ID] = {
[READING_FIRMWARE] = FIRMWARE_CHECK,
[READING_MODULE] = MODULE_CHECK,
+ [READING_MODULE_COMPRESSED] = MODULE_CHECK,
[READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
[READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
[READING_POLICY] = POLICY_CHECK
@@ -917,7 +925,7 @@ static int ima_post_read_file(struct file *file, char *buf, loff_t size,
func = read_idmap[read_id] ?: FILE_CHECK;
security_current_getlsmprop_subj(&prop);
return process_measurement(file, current_cred(), &prop, buf, size,
- MAY_READ, func);
+ MAY_READ, func, read_id);
}
/**
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 164d62832f8e..7468afaab686 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -244,7 +244,8 @@ static struct ima_rule_entry build_appraise_rules[] __ro_after_init = {
static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
{.action = APPRAISE, .func = MODULE_CHECK,
- .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+ .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED | IMA_MODSIG_ALLOWED |
+ IMA_CHECK_BLACKLIST},
{.action = APPRAISE, .func = FIRMWARE_CHECK,
.flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index d0323b81cd8f..1053a4acf589 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -118,6 +118,7 @@ int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
op = IPE_OP_FIRMWARE;
break;
case READING_MODULE:
+ case READING_MODULE_COMPRESSED:
op = IPE_OP_KERNEL_MODULE;
break;
case READING_KEXEC_INITRAMFS:
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index dfc22da42f30..c1ff69d5d76e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4275,7 +4275,7 @@ static int selinux_kernel_read_file(struct file *file,
{
int rc = 0;
- BUILD_BUG_ON_MSG(READING_MAX_ID > 7,
+ BUILD_BUG_ON_MSG(READING_MAX_ID > 8,
"New kernel_read_file_id introduced; update SELinux!");
switch (id) {
@@ -4283,6 +4283,7 @@ static int selinux_kernel_read_file(struct file *file,
rc = selinux_kernel_load_from_file(file, SYSTEM__FIRMWARE_LOAD);
break;
case READING_MODULE:
+ case READING_MODULE_COMPRESSED:
rc = selinux_kernel_load_from_file(file, SYSTEM__MODULE_LOAD);
break;
case READING_KEXEC_IMAGE:
@@ -4311,7 +4312,7 @@ static int selinux_kernel_load_data(enum kernel_load_data_id id, bool contents)
{
int rc = 0;
- BUILD_BUG_ON_MSG(LOADING_MAX_ID > 7,
+ BUILD_BUG_ON_MSG(LOADING_MAX_ID > 8,
"New kernel_load_data_id introduced; update SELinux!");
switch (id) {
base-commit: 43369273518f57b7d56c1cf12d636a809b7bd81b
--
2.51.1
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