This is a note to let you know that I've just added the patch titled binder: use cred instead of task for getsecid to the 5.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: binder-use-cred-instead-of-task-for-getsecid.patch and it can be found in the queue-5.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4d5b5539742d2554591751b4248b0204d20dcc9d Mon Sep 17 00:00:00 2001 From: Todd Kjos <tkjos@xxxxxxxxxx> Date: Tue, 12 Oct 2021 09:56:14 -0700 Subject: binder: use cred instead of task for getsecid From: Todd Kjos <tkjos@xxxxxxxxxx> commit 4d5b5539742d2554591751b4248b0204d20dcc9d upstream. Use the 'struct cred' saved at binder_open() to lookup the security ID via security_cred_getsecid(). This ensures that the security context that opened binder is the one used to generate the secctx. Cc: stable@xxxxxxxxxxxxxxx # 5.4+ Fixes: ec74136ded79 ("binder: create node flag to request sender's security context") Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx> Suggested-by: Stephen Smalley <stephen.smalley.work@xxxxxxxxx> Reported-by: kernel test robot <lkp@xxxxxxxxx> Acked-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx> Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/android/binder.c | 11 +---------- include/linux/security.h | 5 +++++ 2 files changed, 6 insertions(+), 10 deletions(-) --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2722,16 +2722,7 @@ static void binder_transaction(struct bi u32 secid; size_t added_size; - /* - * Arguably this should be the task's subjective LSM secid but - * we can't reliably access the subjective creds of a task - * other than our own so we must use the objective creds, which - * are safe to access. The downside is that if a task is - * temporarily overriding it's creds it will not be reflected - * here; however, it isn't clear that binder would handle that - * case well anyway. - */ - security_task_getsecid_obj(proc->tsk, &secid); + security_cred_getsecid(proc->cred, &secid); ret = security_secid_to_secctx(secid, &secctx, &secctx_sz); if (ret) { return_error = BR_FAILED_REPLY; --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1041,6 +1041,11 @@ static inline void security_transfer_cre { } +static inline void security_cred_getsecid(const struct cred *c, u32 *secid) +{ + *secid = 0; +} + static inline int security_kernel_act_as(struct cred *cred, u32 secid) { return 0; Patches currently in stable-queue which might be from tkjos@xxxxxxxxxx are queue-5.14/binder-use-cred-instead-of-task-for-selinux-checks.patch queue-5.14/binder-don-t-detect-sender-target-during-buffer-cleanup.patch queue-5.14/binder-use-cred-instead-of-task-for-getsecid.patch queue-5.14/binder-use-euid-from-cred-instead-of-using-task.patch