Commit-ID: a21294644623ee41034db60e93aaebed4db0e57b Gitweb: http://git.kernel.org/tip/a21294644623ee41034db60e93aaebed4db0e57b Author: Oleg Nesterov <[email protected]> AuthorDate: Mon, 2 Feb 2015 15:05:36 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 18 Feb 2015 16:57:09 +0100
locking/futex: Check PF_KTHREAD rather than !p->mm to filter out kthreads attach_to_pi_owner() checks p->mm to prevent attaching to kthreads and this looks doubly wrong: 1. It should actually check PF_KTHREAD, kthread can do use_mm(). 2. If this task is not kthread and it is actually the lock owner we can wrongly return -EPERM instead of -ESRCH or retry-if-EAGAIN. And note that this wrong EPERM is the likely case unless the exiting task is (auto)reaped quickly, we check ->mm before PF_EXITING. Signed-off-by: Oleg Nesterov <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Darren Hart <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Jerome Marchand <[email protected]> Cc: Larry Woodman <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mateusz Guzik <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/futex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index 4eeb63d..1f6d646 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -900,7 +900,7 @@ static int attach_to_pi_owner(u32 uval, union futex_key *key, if (!p) return -ESRCH; - if (!p->mm) { + if (unlikely(p->flags & PF_KTHREAD)) { put_task_struct(p); return -EPERM; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
