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binder: use cred instead of task for selinux checks

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commit 52f88693378a58094c538662ba652aff0253c4fe upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Todd Kjos
2021-11-10 15:00:35 -08:00
committed by Greg Kroah-Hartman
parent bd9cea41ac
commit 0d9f4ae7cd
6 changed files with 56 additions and 62 deletions
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14
include/linux/lsm_hook_defs.h
View File

@@ -26,13 +26,13 @@
* #undef LSM_HOOK
* };
*/
LSM_HOOK(int, 0, binder_set_context_mgr, struct task_struct *mgr)
LSM_HOOK(int, 0, binder_transaction, struct task_struct *from,
struct task_struct *to)
LSM_HOOK(int, 0, binder_transfer_binder, struct task_struct *from,
struct task_struct *to)
LSM_HOOK(int, 0, binder_transfer_file, struct task_struct *from,
struct task_struct *to, struct file *file)
LSM_HOOK(int, 0, binder_set_context_mgr, const struct cred *mgr)
LSM_HOOK(int, 0, binder_transaction, const struct cred *from,
const struct cred *to)
LSM_HOOK(int, 0, binder_transfer_binder, const struct cred *from,
const struct cred *to)
LSM_HOOK(int, 0, binder_transfer_file, const struct cred *from,
const struct cred *to, struct file *file)
LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
unsigned int mode)
LSM_HOOK(int, 0, ptrace_traceme, struct task_struct *parent)