The patch titled Subject: cred: remove task_is_dead() from __task_cred() validation has been added to the -mm tree. Its filename is cred-remove-task_is_dead-from-__task_cred-validation.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Oleg Nesterov <oleg@xxxxxxxxxx> Subject: cred: remove task_is_dead() from __task_cred() validation commit 8f92054e ("CRED: Fix __task_cred()'s lockdep check and banner comment"): add the following validation condition: task->exit_state >= 0 to permit the access if the target task is dead and therefore unable to change its own credentials. OK, but afaics currently this can only help wait_task_zombie() which calls __task_cred() without rcu lock. Remove this validation and change wait_task_zombie() to use task_uid() instead. This means we do rcu_read_lock() only to shut up the lockdep, but we already do the same in, say, wait_task_stopped(). task_is_dead() should die, task->exit_state != 0 means that this task has passed exit_notify(), only do_wait-like code paths should use this. Unfortunately, we can't kill task_is_dead() right now, it has already acquired buggy users in drivers/staging. The fix already exists. Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Reviewed-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Acked-by: David Howells <dhowells@xxxxxxxxxx> Cc: Jiri Olsa <jolsa@xxxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: James Morris <jmorris@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/cred.h | 10 +++------- kernel/exit.c | 2 +- 2 files changed, 4 insertions(+), 8 deletions(-) diff -puN include/linux/cred.h~cred-remove-task_is_dead-from-__task_cred-validation include/linux/cred.h --- a/include/linux/cred.h~cred-remove-task_is_dead-from-__task_cred-validation +++ a/include/linux/cred.h @@ -276,17 +276,13 @@ static inline void put_cred(const struct * @task: The task to query * * Access the objective credentials of a task. The caller must hold the RCU - * readlock or the task must be dead and unable to change its own credentials. + * readlock. * * The result of this function should not be passed directly to get_cred(); * rather get_task_cred() should be used instead. */ -#define __task_cred(task) \ - ({ \ - const struct task_struct *__t = (task); \ - rcu_dereference_check(__t->real_cred, \ - task_is_dead(__t)); \ - }) +#define __task_cred(task) \ + rcu_dereference((task)->real_cred) /** * get_current_cred - Get the current task's subjective credentials diff -puN kernel/exit.c~cred-remove-task_is_dead-from-__task_cred-validation kernel/exit.c --- a/kernel/exit.c~cred-remove-task_is_dead-from-__task_cred-validation +++ a/kernel/exit.c @@ -1214,7 +1214,7 @@ static int wait_task_zombie(struct wait_ unsigned long state; int retval, status, traced; pid_t pid = task_pid_vnr(p); - uid_t uid = __task_cred(p)->uid; + uid_t uid = task_uid(p); struct siginfo __user *infop; if (!likely(wo->wo_flags & WEXITED)) _ Subject: Subject: cred: remove task_is_dead() from __task_cred() validation Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch linux-next.patch avr32-dont-mask-signals-in-the-error-path.patch avr32-use-set_current_blocked-in-handle_signal-sys_rt_sigreturn.patch avr32-use-block_sigmask.patch m32r-use-set_current_blocked-and-block_sigmask.patch m68k-use-set_current_blocked-and-block_sigmask.patch mn10300-use-set_current_blocked-and-block_sigmask.patch cris-use-set_current_blocked-and-block_sigmask.patch ia64-use-set_current_blocked-and-block_sigmask.patch microblaze-dont-reimplement-force_sigsegv.patch microblaze-no-need-to-reset-handler-if-sa_oneshot.patch microblaze-fix-signal-masking.patch microblaze-use-set_current_blocked-and-block_sigmask.patch mips-use-set_current_blocked-and-block_sigmask.patch score-dont-mask-signals-if-we-fail-to-setup-signal-stack.patch score-use-set_current_blocked-and-block_sigmask.patch h8300-use-set_current_blocked-and-block_sigmask.patch unicore32-use-block_sigmask.patch blackfin-use-set_current_blocked-and-block_sigmask.patch frv-use-set_current_blocked-and-block_sigmask.patch parisc-use-set_current_blocked-and-block_sigmask.patch kmod-unexport-call_usermodehelper_freeinfo.patch kmod-convert-two-call-sites-to-call_usermodehelper_fns.patch kmod-move-call_usermodehelper_fns-to-c-file-and-unexport-all-its-helpers.patch cred-remove-task_is_dead-from-__task_cred-validation.patch proc-clean-up-proc-pid-environ-handling.patch proc-unify-ptrace_may_access-locking-code.patch proc-remove-mm_for_maps.patch proc-use-mm_access-instead-of-ptrace_may_access.patch proc-use-task_access_lock-instead-of-ptrace_may_access.patch proc-use-is_err_or_null.patch sysctl-make-kernelns_last_pid-control-being-checkpoint_restore-dependent.patch fs-proc-introduce-proc-pid-task-tid-children-entry-v9.patch c-r-prctl-add-ability-to-set-new-mm_struct-exe_file.patch c-r-prctl-add-ability-to-get-clear_tid_address.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html