diff options
| author | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2018-12-03 15:04:18 +0300 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2018-12-04 18:04:20 +0300 |
| commit | a72173ecfc6774cf2d55de9fb29421ce69e3428c (patch) | |
| tree | a36bb49798f5f934e3a418ab3a7ab84076857346 | |
| parent | 2595646791c319cadfdbf271563aac97d0843dc7 (diff) | |
| download | linux-a72173ecfc6774cf2d55de9fb29421ce69e3428c.tar.xz | |
Revert "exec: make de_thread() freezable"
Revert commit c22397888f1e "exec: make de_thread() freezable" as
requested by Ingo Molnar:
"So there's a new regression in v4.20-rc4, my desktop produces this
lockdep splat:
[ 1772.588771] WARNING: pkexec/4633 still has locks held!
[ 1772.588773] 4.20.0-rc4-custom-00213-g93a49841322b #1 Not tainted
[ 1772.588775] ------------------------------------
[ 1772.588776] 1 lock held by pkexec/4633:
[ 1772.588778] #0: 00000000ed85fbf8 (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x2a/0x70
[ 1772.588786] stack backtrace:
[ 1772.588789] CPU: 7 PID: 4633 Comm: pkexec Not tainted 4.20.0-rc4-custom-00213-g93a49841322b #1
[ 1772.588792] Call Trace:
[ 1772.588800] dump_stack+0x85/0xcb
[ 1772.588803] flush_old_exec+0x116/0x890
[ 1772.588807] ? load_elf_phdrs+0x72/0xb0
[ 1772.588809] load_elf_binary+0x291/0x1620
[ 1772.588815] ? sched_clock+0x5/0x10
[ 1772.588817] ? search_binary_handler+0x6d/0x240
[ 1772.588820] search_binary_handler+0x80/0x240
[ 1772.588823] load_script+0x201/0x220
[ 1772.588825] search_binary_handler+0x80/0x240
[ 1772.588828] __do_execve_file.isra.32+0x7d2/0xa60
[ 1772.588832] ? strncpy_from_user+0x40/0x180
[ 1772.588835] __x64_sys_execve+0x34/0x40
[ 1772.588838] do_syscall_64+0x60/0x1c0
The warning gets triggered by an ancient lockdep check in the freezer:
(gdb) list *0xffffffff812ece06
0xffffffff812ece06 is in flush_old_exec (./include/linux/freezer.h:57).
52 * DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION
53 * If try_to_freeze causes a lockdep warning it means the caller may deadlock
54 */
55 static inline bool try_to_freeze_unsafe(void)
56 {
57 might_sleep();
58 if (likely(!freezing(current)))
59 return false;
60 return __refrigerator(false);
61 }
I reviewed the ->cred_guard_mutex code, and the mutex is held across all
of exec() - and we always did this.
But there's this recent -rc4 commit:
> Chanho Min (1):
> exec: make de_thread() freezable
c22397888f1e: exec: make de_thread() freezable
I believe this commit is bogus, you cannot call try_to_freeze() from
de_thread(), because it's holding the ->cred_guard_mutex."
Reported-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | fs/exec.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/exec.c b/fs/exec.c index acc3a5536384..fc281b738a98 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -62,7 +62,6 @@ #include <linux/oom.h> #include <linux/compat.h> #include <linux/vmalloc.h> -#include <linux/freezer.h> #include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -1084,7 +1083,7 @@ static int de_thread(struct task_struct *tsk) while (sig->notify_count) { __set_current_state(TASK_KILLABLE); spin_unlock_irq(lock); - freezable_schedule(); + schedule(); if (unlikely(__fatal_signal_pending(tsk))) goto killed; spin_lock_irq(lock); @@ -1112,7 +1111,7 @@ static int de_thread(struct task_struct *tsk) __set_current_state(TASK_KILLABLE); write_unlock_irq(&tasklist_lock); cgroup_threadgroup_change_end(tsk); - freezable_schedule(); + schedule(); if (unlikely(__fatal_signal_pending(tsk))) goto killed; } |