If a file is closed before it is munmapped, __fput() is called with
the mmap_sem taken. With IMA-appraisal enabled, this results in an
mmap_sem/i_mutex lockdep. ima_defer_fput() increments the f_count
to defer __fput() being called until after the mmap_sem is released.
Changelog v3:
- use slab mempool (suggested by Dmitry Kasatkin)
- renamed a few functions based on Matt Helsley's review
- define ima_fput_mempool as static (fix sparse error)
- fix ima_defer_fput() stub definition
Changelog v2:
- based on discussions with: Tyler Hicks (use workqueues),
Dave Hansen (defer only IMA related files), and
Dmitry Kasatkin (add new IMA hook)
- use slab memory for allocating work
Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxx>
---
include/linux/ima.h | 5 ++
mm/mmap.c | 1 +
security/integrity/ima/ima_appraise.c | 84 +++++++++++++++++++++++++++++++++
3 files changed, 90 insertions(+), 0 deletions(-)
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 2c7223d..af8cb3b 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -47,6 +47,7 @@ extern void ima_inode_post_setattr(struct dentry *dentry);
extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len);
extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
+extern void ima_defer_fput(struct file *file);
#else
static inline void ima_inode_post_setattr(struct dentry *dentry)
{
@@ -66,5 +67,9 @@ static inline int ima_inode_removexattr(struct dentry *dentry,
{
return 0;
}
+static inline void ima_defer_fput(struct file *file)
+{
+ return;
+}
#endif /* CONFIG_IMA_APPRAISE_H */
#endif /* _LINUX_IMA_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index 4c16a0a..c1accd4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -232,6 +232,7 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
if (vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file) {
+ ima_defer_fput(vma->vm_file); /* drop mmap_sem first */
fput(vma->vm_file);
if (vma->vm_flags & VM_EXECUTABLE)
removed_exe_file_vma(vma->vm_mm);
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index becc7e0..a100a3c 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -11,6 +11,7 @@
#include <linux/module.h>
#include <linux/file.h>
#include <linux/fs.h>
+#include <linux/mempool.h>
#include <linux/xattr.h>
#include <linux/magic.h>
#include <linux/ima.h>
@@ -226,3 +227,86 @@ int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name)
}
return result;
}
+
+struct ima_fput_req {
+ struct file *file;
+ struct work_struct work;
+};
+static struct kmem_cache *ima_fput_slab;
+static mempool_t *ima_fput_mempool;
+
+static void ima_deferred_fput(struct work_struct *work)
+{
+ struct ima_fput_req *deferred = container_of(work, struct ima_fput_req,
+ work);
+
+ fput(deferred->file);
+ mempool_free(deferred, ima_fput_mempool);
+}
+
+/**
+ * ima_defer_fput - defer calling __fput() for mmaped files
+ * @file: pointer to file structure to be freed
+ *
+ * The i_mutex is taken by ima_file_free(), called on __fput(), to
+ * update 'security.ima' to reflect the current file data hash. When
+ * a file is closed before it is munmapped, __fput() is called with
+ * the mmap_sem taken, resulting in an mmap_sem/i_mutex lockdep.
+ * This function defers calling __fput() until after the mmap_sem is
+ * released.
+ */
+void ima_defer_fput(struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+ struct ima_fput_req *defer;
+ int rc;
+
+ if (!IS_IMA(inode))
+ return;
+
+ defer = mempool_alloc(ima_fput_mempool, GFP_NOIO);
+ if (!defer)
+ return;
+
+ get_file(file);
+
+ defer->file = file;
+ INIT_WORK(&defer->work, ima_deferred_fput);
+ rc = schedule_work(&defer->work);
+ if (rc == 0) {
+ pr_info("ima: schedule work failed\n");
+ mempool_free(defer, ima_fput_mempool);
+ fput_atomic(file);
+ }
+}
+
+static int __init ima_fput_mempool_create(void)
+{
+ ima_fput_slab = kmem_cache_create("ima_fput",
+ sizeof(struct ima_fput_req),
+ 0, 0, NULL);
+ if (!ima_fput_slab) {
+ pr_info("ima: failed kmem_cache_create\n");
+ goto err_out;
+ }
+
+ ima_fput_mempool = mempool_create_slab_pool(1, ima_fput_slab);
+ if (!ima_fput_mempool) {
+ pr_info("ima: failed mempool_create_slab_pool\n");
+ goto free_slab;
+ }
+ return 0;
+
+free_slab:
+ kmem_cache_destroy(ima_fput_slab);
+err_out:
+ return -ENOMEM;
+}
+
+static void __exit ima_fput_mempool_destroy(void)
+{
+ mempool_destroy(ima_fput_mempool);
+ kmem_cache_destroy(ima_fput_slab);
+}
+security_initcall(ima_fput_mempool_create);
--
1.7.6.5
--
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