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BACKPORT: 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>
Bug: 200688826
(cherry picked from commit 52f88693378a58094c538662ba652aff0253c4fe)
[ refactored to avoid changing KMI: struct binder_proc ]
Change-Id: I1664c1f0c2142c17e9ca0d6790bb94de79f531e3
This commit is contained in:
Todd Kjos
2021-10-12 09:56:13 -07:00
parent d492977395
commit 3af7a2f610
6 changed files with 59 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)