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fix ima breakage
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The "Untangling ima mess, part 2 with counters" patch messed
up the counters.  Based on conversations with Al Viro, this patch
streamlines ima_path_check() by removing the counter maintaince.
The counters are now updated independently, from measuring the file,
in __dentry_open() and alloc_file() by calling ima_counts_get().
ima_path_check() is called from nfsd and do_filp_open().
It also did not measure all files that should have been measured.
Reason: ima_path_check() got bogus value passed as mask.
[AV: mea culpa]
[AV: add missing nfsd bits]

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Mimi Zohar authored and Al Viro committed Feb 7, 2010
1 parent 1e41568 commit 8eb988c
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Showing 4 changed files with 97 additions and 152 deletions.
6 changes: 2 additions & 4 deletions fs/namei.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1736,8 +1736,7 @@ struct file *do_filp_open(int dfd, const char *pathname,
if (nd.root.mnt)
path_put(&nd.root);
if (!IS_ERR(filp)) {
error = ima_path_check(&filp->f_path, filp->f_mode &
(MAY_READ | MAY_WRITE | MAY_EXEC));
error = ima_path_check(filp, acc_mode);
if (error) {
fput(filp);
filp = ERR_PTR(error);
Expand Down Expand Up @@ -1797,8 +1796,7 @@ struct file *do_filp_open(int dfd, const char *pathname,
}
filp = nameidata_to_filp(&nd);
if (!IS_ERR(filp)) {
error = ima_path_check(&filp->f_path, filp->f_mode &
(MAY_READ | MAY_WRITE | MAY_EXEC));
error = ima_path_check(filp, acc_mode);
if (error) {
fput(filp);
filp = ERR_PTR(error);
Expand Down
3 changes: 1 addition & 2 deletions fs/nfsd/vfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -752,8 +752,7 @@ nfsd_open(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
flags, current_cred());
if (IS_ERR(*filp))
host_err = PTR_ERR(*filp);
host_err = ima_path_check(&(*filp)->f_path,
access & (MAY_READ | MAY_WRITE | MAY_EXEC));
host_err = ima_path_check(*filp, access);
out_nfserr:
err = nfserrno(host_err);
out:
Expand Down
4 changes: 2 additions & 2 deletions include/linux/ima.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ struct linux_binprm;
extern int ima_bprm_check(struct linux_binprm *bprm);
extern int ima_inode_alloc(struct inode *inode);
extern void ima_inode_free(struct inode *inode);
extern int ima_path_check(struct path *path, int mask);
extern int ima_path_check(struct file *file, int mask);
extern void ima_file_free(struct file *file);
extern int ima_file_mmap(struct file *file, unsigned long prot);
extern void ima_counts_get(struct file *file);
Expand All @@ -38,7 +38,7 @@ static inline void ima_inode_free(struct inode *inode)
return;
}

static inline int ima_path_check(struct path *path, int mask)
static inline int ima_path_check(struct file *file, int mask)
{
return 0;
}
Expand Down
236 changes: 92 additions & 144 deletions security/integrity/ima/ima_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,36 @@ static bool ima_limit_imbalance(struct file *file)
return found;
}

/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
*
* When opening a file for read, if the file is already open for write,
* the file could change, resulting in a file measurement error.
*
* Opening a file for write, if the file is already open for read, results
* in a time of measure, time of use (ToMToU) error.
*
* In either case invalidate the PCR.
*/
enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
static void ima_read_write_check(enum iint_pcr_error error,
struct ima_iint_cache *iint,
struct inode *inode,
const unsigned char *filename)
{
switch (error) {
case TOMTOU:
if (iint->readcount > 0)
ima_add_violation(inode, filename, "invalid_pcr",
"ToMToU");
break;
case OPEN_WRITERS:
if (iint->writecount > 0)
ima_add_violation(inode, filename, "invalid_pcr",
"open_writers");
break;
}
}

/*
* Update the counts given an fmode_t
*/
Expand All @@ -98,6 +128,47 @@ static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
iint->writecount++;
}

/*
* ima_counts_get - increment file counts
*
* Maintain read/write counters for all files, but only
* invalidate the PCR for measured files:
* - Opening a file for write when already open for read,
* results in a time of measure, time of use (ToMToU) error.
* - Opening a file for read when already open for write,
* could result in a file measurement error.
*
*/
void ima_counts_get(struct file *file)
{
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
fmode_t mode = file->f_mode;
struct ima_iint_cache *iint;
int rc;

if (!ima_initialized || !S_ISREG(inode->i_mode))
return;
iint = ima_iint_find_get(inode);
if (!iint)
return;
mutex_lock(&iint->mutex);
rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
if (rc < 0)
goto out;

if (mode & FMODE_WRITE) {
ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
goto out;
}
ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
out:
ima_inc_counts(iint, file->f_mode);
mutex_unlock(&iint->mutex);

kref_put(&iint->refcount, iint_free);
}

/*
* Decrement ima counts
*/
Expand Down Expand Up @@ -153,123 +224,6 @@ void ima_file_free(struct file *file)
kref_put(&iint->refcount, iint_free);
}

/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
*
* When opening a file for read, if the file is already open for write,
* the file could change, resulting in a file measurement error.
*
* Opening a file for write, if the file is already open for read, results
* in a time of measure, time of use (ToMToU) error.
*
* In either case invalidate the PCR.
*/
enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
static void ima_read_write_check(enum iint_pcr_error error,
struct ima_iint_cache *iint,
struct inode *inode,
const unsigned char *filename)
{
switch (error) {
case TOMTOU:
if (iint->readcount > 0)
ima_add_violation(inode, filename, "invalid_pcr",
"ToMToU");
break;
case OPEN_WRITERS:
if (iint->writecount > 0)
ima_add_violation(inode, filename, "invalid_pcr",
"open_writers");
break;
}
}

static int get_path_measurement(struct ima_iint_cache *iint, struct file *file,
const unsigned char *filename)
{
int rc = 0;

ima_inc_counts(iint, file->f_mode);

rc = ima_collect_measurement(iint, file);
if (!rc)
ima_store_measurement(iint, file, filename);
return rc;
}

/**
* ima_path_check - based on policy, collect/store measurement.
* @path: contains a pointer to the path to be measured
* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
*
* Measure the file being open for readonly, based on the
* ima_must_measure() policy decision.
*
* Keep read/write counters for all files, but only
* invalidate the PCR for measured files:
* - Opening a file for write when already open for read,
* results in a time of measure, time of use (ToMToU) error.
* - Opening a file for read when already open for write,
* could result in a file measurement error.
*
* Always return 0 and audit dentry_open failures.
* (Return code will be based upon measurement appraisal.)
*/
int ima_path_check(struct path *path, int mask)
{
struct inode *inode = path->dentry->d_inode;
struct ima_iint_cache *iint;
struct file *file = NULL;
int rc;

if (!ima_initialized || !S_ISREG(inode->i_mode))
return 0;
iint = ima_iint_find_get(inode);
if (!iint)
return 0;

mutex_lock(&iint->mutex);

rc = ima_must_measure(iint, inode, MAY_READ, PATH_CHECK);
if (rc < 0)
goto out;

if ((mask & MAY_WRITE) || (mask == 0))
ima_read_write_check(TOMTOU, iint, inode,
path->dentry->d_name.name);

if ((mask & (MAY_WRITE | MAY_READ | MAY_EXEC)) != MAY_READ)
goto out;

ima_read_write_check(OPEN_WRITERS, iint, inode,
path->dentry->d_name.name);
if (!(iint->flags & IMA_MEASURED)) {
struct dentry *dentry = dget(path->dentry);
struct vfsmount *mnt = mntget(path->mnt);

file = dentry_open(dentry, mnt, O_RDONLY | O_LARGEFILE,
current_cred());
if (IS_ERR(file)) {
int audit_info = 0;

integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
dentry->d_name.name,
"add_measurement",
"dentry_open failed",
1, audit_info);
file = NULL;
goto out;
}
rc = get_path_measurement(iint, file, dentry->d_name.name);
}
out:
mutex_unlock(&iint->mutex);
if (file)
fput(file);
kref_put(&iint->refcount, iint_free);
return 0;
}
EXPORT_SYMBOL_GPL(ima_path_check);

static int process_measurement(struct file *file, const unsigned char *filename,
int mask, int function)
{
Expand Down Expand Up @@ -297,33 +251,6 @@ static int process_measurement(struct file *file, const unsigned char *filename,
return rc;
}

/*
* ima_counts_get - increment file counts
*
* - for IPC shm and shmat file.
* - for nfsd exported files.
*
* Increment the counts for these files to prevent unnecessary
* imbalance messages.
*/
void ima_counts_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_get(inode);
if (!iint)
return;
mutex_lock(&iint->mutex);
ima_inc_counts(iint, file->f_mode);
mutex_unlock(&iint->mutex);

kref_put(&iint->refcount, iint_free);
}
EXPORT_SYMBOL_GPL(ima_counts_get);

/**
* ima_file_mmap - based on policy, collect/store measurement.
* @file: pointer to the file to be measured (May be NULL)
Expand Down Expand Up @@ -369,6 +296,27 @@ int ima_bprm_check(struct linux_binprm *bprm)
return 0;
}

/**
* ima_path_check - based on policy, collect/store measurement.
* @file: pointer to the file to be measured
* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
*
* Measure files based on the ima_must_measure() policy decision.
*
* Always return 0 and audit dentry_open failures.
* (Return code will be based upon measurement appraisal.)
*/
int ima_path_check(struct file *file, int mask)
{
int rc;

rc = process_measurement(file, file->f_dentry->d_name.name,
mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
PATH_CHECK);
return 0;
}
EXPORT_SYMBOL_GPL(ima_path_check);

static int __init init_ima(void)
{
int error;
Expand Down

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