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
