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    Subject[PATCH 6/6] Integrity: IMA file free imbalance
    Date
    The number of calls to ima_path_check()/ima_file_free()
    should be balanced. An extra call to fput(), indicates
    the file could have been accessed without first being
    measured.

    Although f_count is incremented/decremented in places other
    than fget/fput, like fget_light/fput_light and get_file, the
    current task must already hold a file refcnt. The call to
    __fput() is delayed until the refcnt becomes 0, resulting
    in ima_file_free() flagging any changes.

    - add hook to increment opencount for IPC shared memory(SYSV)
    and shmat files

    Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
    ---
    diff --git a/include/linux/ima.h b/include/linux/ima.h
    index dcc3664..6db30a3 100644
    --- a/include/linux/ima.h
    +++ b/include/linux/ima.h
    @@ -19,6 +19,7 @@ extern void ima_inode_free(struct inode *inode);
    extern int ima_path_check(struct path *path, int mask);
    extern void ima_file_free(struct file *file);
    extern int ima_file_mmap(struct file *file, unsigned long prot);
    +extern void ima_shm_check(struct file *file);

    #else
    static inline int ima_bprm_check(struct linux_binprm *bprm)
    @@ -50,5 +51,10 @@ static inline int ima_file_mmap(struct file *file, unsigned long prot)
    {
    return 0;
    }
    +
    +static inline void ima_shm_check(struct file *file)
    +{
    + return;
    +}
    #endif /* CONFIG_IMA_H */
    #endif /* _LINUX_IMA_H */
    diff --git a/ipc/shm.c b/ipc/shm.c
    index a9e09ad..5604bc8 100644
    --- a/ipc/shm.c
    +++ b/ipc/shm.c
    @@ -39,6 +39,7 @@
    #include <linux/nsproxy.h>
    #include <linux/mount.h>
    #include <linux/ipc_namespace.h>
    +#include <linux/ima.h>

    #include <asm/uaccess.h>

    @@ -381,6 +382,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
    error = PTR_ERR(file);
    if (IS_ERR(file))
    goto no_file;
    + ima_shm_check(file);

    id = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
    if (id < 0) {
    @@ -881,6 +883,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
    file = alloc_file(path.mnt, path.dentry, f_mode, &shm_file_operations);
    if (!file)
    goto out_free;
    + ima_shm_check(file);

    file->private_data = sfd;
    file->f_mapping = shp->shm_file->f_mapping;
    diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
    index 5b72cdb..ed953fb 100644
    --- a/security/integrity/ima/ima.h
    +++ b/security/integrity/ima/ima.h
    @@ -98,6 +98,7 @@ static inline unsigned long ima_hash_key(u8 *digest)

    /* iint cache flags */
    #define IMA_MEASURED 1
    +#define IMA_IINT_DUMP_STACK 512

    /* integrity data associated with an inode */
    struct ima_iint_cache {
    @@ -107,6 +108,7 @@ struct ima_iint_cache {
    struct mutex mutex; /* protects: version, flags, digest */
    long readcount; /* measured files readcount */
    long writecount; /* measured files writecount */
    + long opencount; /* opens reference count */
    struct kref refcount; /* ima_iint_cache reference count */
    struct rcu_head rcu;
    };
    diff --git a/security/integrity/ima/ima_iint.c b/security/integrity/ima/ima_iint.c
    index 750db3c..1f035e8 100644
    --- a/security/integrity/ima/ima_iint.c
    +++ b/security/integrity/ima/ima_iint.c
    @@ -126,6 +126,7 @@ struct ima_iint_cache *ima_iint_find_insert_get(struct inode *inode)

    return iint;
    }
    +EXPORT_SYMBOL_GPL(ima_iint_find_insert_get);

    /* iint_free - called when the iint refcount goes to zero */
    void iint_free(struct kref *kref)
    @@ -134,6 +135,21 @@ void iint_free(struct kref *kref)
    refcount);
    iint->version = 0;
    iint->flags = 0UL;
    + if (iint->readcount != 0) {
    + printk(KERN_INFO "%s: readcount: %ld\n", __FUNCTION__,
    + iint->readcount);
    + iint->readcount = 0;
    + }
    + if (iint->writecount != 0) {
    + printk(KERN_INFO "%s: writecount: %ld\n", __FUNCTION__,
    + iint->writecount);
    + iint->writecount = 0;
    + }
    + if (iint->opencount != 0) {
    + printk(KERN_INFO "%s: opencount: %ld\n", __FUNCTION__,
    + iint->opencount);
    + iint->opencount = 0;
    + }
    kref_set(&iint->refcount, 1);
    kmem_cache_free(iint_cache, iint);
    }
    @@ -174,6 +190,7 @@ static void init_once(void *foo)
    mutex_init(&iint->mutex);
    iint->readcount = 0;
    iint->writecount = 0;
    + iint->opencount = 0;
    kref_set(&iint->refcount, 1);
    }

    diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
    index 871e356..751a5d2 100644
    --- a/security/integrity/ima/ima_main.c
    +++ b/security/integrity/ima/ima_main.c
    @@ -66,6 +66,19 @@ void ima_file_free(struct file *file)
    return;

    mutex_lock(&iint->mutex);
    + if (iint->opencount <= 0) {
    + printk(KERN_INFO
    + "%s: %s open/free imbalance (r:%ld w:%ld o:%ld f:%ld)\n",
    + __FUNCTION__, file->f_dentry->d_name.name,
    + iint->readcount, iint->writecount,
    + iint->opencount, atomic_long_read(&file->f_count));
    + if (!(iint->flags & IMA_IINT_DUMP_STACK)) {
    + dump_stack();
    + iint->flags |= IMA_IINT_DUMP_STACK;
    + }
    + }
    + iint->opencount--;
    +
    if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
    iint->readcount--;

    @@ -119,6 +132,7 @@ static int get_path_measurement(struct ima_iint_cache *iint, struct file *file,
    pr_info("%s dentry_open failed\n", filename);
    return rc;
    }
    + iint->opencount++;
    iint->readcount++;

    rc = ima_collect_measurement(iint, file);
    @@ -159,6 +173,7 @@ int ima_path_check(struct path *path, int mask)
    return 0;

    mutex_lock(&iint->mutex);
    + iint->opencount++;
    if ((mask & MAY_WRITE) || (mask == 0))
    iint->writecount++;
    else if (mask & (MAY_READ | MAY_EXEC))
    @@ -219,6 +234,20 @@ out:
    return rc;
    }

    +static void opencount_get(struct file *file)
    +{
    + struct inode *inode = file->f_dentry->d_inode;
    + struct ima_iint_cache *iint;
    +
    + if (!ima_initialized || !S_ISREG(inode->i_mode))
    + return;
    + iint = ima_iint_find_insert_get(inode);
    + mutex_lock(&iint->mutex);
    + if (iint)
    + iint->opencount++;
    + mutex_unlock(&iint->mutex);
    +}
    +
    /**
    * ima_file_mmap - based on policy, collect/store measurement.
    * @file: pointer to the file to be measured (May be NULL)
    @@ -242,6 +271,18 @@ int ima_file_mmap(struct file *file, unsigned long prot)
    return 0;
    }

    +/*
    + * ima_shm_check - IPC shm and shmat create/fput a file
    + *
    + * Maintain the opencount for these files to prevent unnecessary
    + * imbalance messages.
    + */
    +void ima_shm_check(struct file *file)
    +{
    + opencount_get(file);
    + return;
    +}
    +
    /**
    * ima_bprm_check - based on policy, collect/store measurement.
    * @bprm: contains the linux_binprm structure
    --
    1.5.6.6


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