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binder: use cred instead of task for selinux checks

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Since binder was integrated with selinux, it has passed
'struct task_struct' associated with the binder_proc
to represent the source and target of transactions.
The conversion of task to SID was then done in the hook
implementations. It turns out that there are race conditions
which can result in an incorrect security context being used.

Fix by using the 'struct cred' saved during binder_open and pass
it to the selinux subsystem.

Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables)
Fixes: 79af73079d ("Add security hooks to binder and implement the hooks for SELinux.")
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Todd Kjos
2021-10-12 09:56:13 -07:00
committed by Paul Moore
parent 29bc22ac5e
commit 52f8869337
6 changed files with 54 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
include/linux/security.h
View File

@@ -258,13 +258,13 @@ extern int security_init(void);
extern int early_security_init(void);
/* Security operations */
int security_binder_set_context_mgr(struct task_struct *mgr);
int security_binder_transaction(struct task_struct *from,
struct task_struct *to);
int security_binder_transfer_binder(struct task_struct *from,
struct task_struct *to);
int security_binder_transfer_file(struct task_struct *from,
struct task_struct *to, struct file *file);
int security_binder_set_context_mgr(const struct cred *mgr);
int security_binder_transaction(const struct cred *from,
const struct cred *to);
int security_binder_transfer_binder(const struct cred *from,
const struct cred *to);
int security_binder_transfer_file(const struct cred *from,
const struct cred *to, struct file *file);
int security_ptrace_access_check(struct task_struct *child, unsigned int mode);
int security_ptrace_traceme(struct task_struct *parent);
int security_capget(struct task_struct *target,
@@ -508,25 +508,25 @@ static inline int early_security_init(void)
return 0;
}
static inline int security_binder_set_context_mgr(struct task_struct *mgr)
static inline int security_binder_set_context_mgr(const struct cred *mgr)
{
return 0;
}
static inline int security_binder_transaction(struct task_struct *from,
struct task_struct *to)
static inline int security_binder_transaction(const struct cred *from,
const struct cred *to)
{
return 0;
}
static inline int security_binder_transfer_binder(struct task_struct *from,
struct task_struct *to)
static inline int security_binder_transfer_binder(const struct cred *from,
const struct cred *to)
{
return 0;
}
static inline int security_binder_transfer_file(struct task_struct *from,
struct task_struct *to,
static inline int security_binder_transfer_file(const struct cred *from,
const struct cred *to,
struct file *file)
{
return 0;