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Smack: Implement lock security mode

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Linux file locking does not follow the same rules
as other mechanisms. Even though it is a write operation
a process can set a read lock on files which it has open
only for read access. Two programs with read access to
a file can use read locks to communicate.

This is not acceptable in a Mandatory Access Control
environment. Smack treats setting a read lock as the
write operation that it is. Unfortunately, many programs
assume that setting a read lock is a read operation.
These programs are unhappy in the Smack environment.

This patch introduces a new access mode (lock) to address
this problem. A process with lock access to a file can
set a read lock. A process with write access to a file can
set a read lock or a write lock. This prevents a situation
where processes are granted write access just so they can
set read locks.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
This commit is contained in:
Casey Schaufler
2013-10-11 18:06:39 -07:00
parent 5a5f2acfd0
commit c0ab6e56dc
4 changed files with 33 additions and 8 deletions
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9
security/smack/smack_lsm.c
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@@ -1146,7 +1146,7 @@ static int smack_file_ioctl(struct file *file, unsigned int cmd,
* @file: the object
* @cmd: unused
*
* Returns 0 if current has write access, error code otherwise
* Returns 0 if current has lock access, error code otherwise
*/
static int smack_file_lock(struct file *file, unsigned int cmd)
{
@@ -1154,7 +1154,7 @@ static int smack_file_lock(struct file *file, unsigned int cmd)
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
smk_ad_setfield_u_fs_path(&ad, file->f_path);
return smk_curacc(file->f_security, MAY_WRITE, &ad);
return smk_curacc(file->f_security, MAY_LOCK, &ad);
}
/**
@@ -1178,8 +1178,13 @@ static int smack_file_fcntl(struct file *file, unsigned int cmd,
switch (cmd) {
case F_GETLK:
break;
case F_SETLK:
case F_SETLKW:
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
smk_ad_setfield_u_fs_path(&ad, file->f_path);
rc = smk_curacc(file->f_security, MAY_LOCK, &ad);
break;
case F_SETOWN:
case F_SETSIG:
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);