linux-kernel - [PATCH v3 1/2] ima: Align ima_file_mmap() parameters with mmap

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Message-Id: <20230126163812.1870942-1-roberto.sassu@huaweicloud.com>
Date:   Thu, 26 Jan 2023 17:38:10 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     zohar@...ux.ibm.com, dmitry.kasatkin@...il.com, jmorris@...ei.org,
        serge@...lyn.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefanb@...ux.ibm.com,
        viro@...iv.linux.org.uk, Roberto Sassu <roberto.sassu@...wei.com>,
        stable@...r.kernel.org
Subject: [PATCH v3 1/2] ima: Align ima_file_mmap() parameters with mmap_file LSM hook

From: Roberto Sassu <roberto.sassu@...wei.com>

Commit 98de59bfe4b2f ("take calculation of final prot in
security_mmap_file() into a helper") moved the code to update prot, to be
the actual protections applied to the kernel, to a new helper called
mmap_prot().

However, while without the helper ima_file_mmap() was getting the updated
prot, with the helper ima_file_mmap() gets the original prot, which
contains the protections requested by the application.

A possible consequence of this change is that, if an application calls
mmap() with only PROT_READ, and the kernel applies PROT_EXEC in addition,
that application would have access to executable memory without having this
event recorded in the IMA measurement list. This situation would occur for
example if the application, before mmap(), calls the personality() system
call with READ_IMPLIES_EXEC as the first argument.

Align ima_file_mmap() parameters with those of the mmap_file LSM hook, so
that IMA can receive both the requested prot and the final prot. Since the
requested protections are stored in a new variable, and the final
protections are stored in the existing variable, this effectively restores
the original behavior of the MMAP_CHECK hook.

Cc: stable@...r.kernel.org
Fixes: 98de59bfe4b2 ("take calculation of final prot in security_mmap_file() into a helper")
Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 include/linux/ima.h               | 6 ++++--
 security/integrity/ima/ima_main.c | 7 +++++--
 security/security.c               | 7 ++++---
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 5a0b2a285a18..d79fee67235e 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -21,7 +21,8 @@ extern int ima_file_check(struct file *file, int mask);
 extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
 				    struct inode *inode);
 extern void ima_file_free(struct file *file);
-extern int ima_file_mmap(struct file *file, unsigned long prot);
+extern int ima_file_mmap(struct file *file, unsigned long reqprot,
+			 unsigned long prot, unsigned long flags);
 extern int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot);
 extern int ima_load_data(enum kernel_load_data_id id, bool contents);
 extern int ima_post_load_data(char *buf, loff_t size,
@@ -76,7 +77,8 @@ static inline void ima_file_free(struct file *file)
 	return;
 }
 
-static inline int ima_file_mmap(struct file *file, unsigned long prot)
+static inline int ima_file_mmap(struct file *file, unsigned long reqprot,
+				unsigned long prot, unsigned long flags)
 {
 	return 0;
 }
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 377300973e6c..f48f4e694921 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -397,7 +397,9 @@ static int process_measurement(struct file *file, const struct cred *cred,
 /**
  * ima_file_mmap - based on policy, collect/store measurement.
  * @file: pointer to the file to be measured (May be NULL)
- * @prot: contains the protection that will be applied by the kernel.
+ * @reqprot: protection requested by the application
+ * @prot: protection that will be applied by the kernel
+ * @flags: operational flags
  *
  * Measure files being mmapped executable based on the ima_must_measure()
  * policy decision.
@@ -405,7 +407,8 @@ static int process_measurement(struct file *file, const struct cred *cred,
  * On success return 0.  On integrity appraisal error, assuming the file
  * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
  */
-int ima_file_mmap(struct file *file, unsigned long prot)
+int ima_file_mmap(struct file *file, unsigned long reqprot,
+		  unsigned long prot, unsigned long flags)
 {
 	u32 secid;
 
diff --git a/security/security.c b/security/security.c
index d1571900a8c7..174afa4fad81 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1661,12 +1661,13 @@ static inline unsigned long mmap_prot(struct file *file, unsigned long prot)
 int security_mmap_file(struct file *file, unsigned long prot,
 			unsigned long flags)
 {
+	unsigned long prot_adj = mmap_prot(file, prot);
 	int ret;
-	ret = call_int_hook(mmap_file, 0, file, prot,
-					mmap_prot(file, prot), flags);
+
+	ret = call_int_hook(mmap_file, 0, file, prot, prot_adj, flags);
 	if (ret)
 		return ret;
-	return ima_file_mmap(file, prot);
+	return ima_file_mmap(file, prot, prot_adj, flags);
 }
 
 int security_mmap_addr(unsigned long addr)
-- 
2.25.1