Commit-ID: 405c0759712f57b680f66aee9c55cd06ad1cbdef Gitweb: http://git.kernel.org/tip/405c0759712f57b680f66aee9c55cd06ad1cbdef Author: Andy Lutomirski <[email protected]> AuthorDate: Mon, 31 Oct 2016 08:11:43 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Tue, 1 Nov 2016 07:39:17 +0100
fork: Add task stack refcounting sanity check and prevent premature task stack freeing If something goes wrong with task stack refcounting and a stack refcount hits zero too early, warn and leak it rather than potentially freeing it early (and silently). Signed-off-by: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/f29119c783a9680a4b4656e751b6123917ace94b.1477926663.git.l...@kernel.org Signed-off-by: Ingo Molnar <[email protected]> --- kernel/fork.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index 623259f..997ac1d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -315,6 +315,9 @@ static void account_kernel_stack(struct task_struct *tsk, int account) static void release_task_stack(struct task_struct *tsk) { + if (WARN_ON(tsk->state != TASK_DEAD)) + return; /* Better to leak the stack than to free prematurely */ + account_kernel_stack(tsk, -1); arch_release_thread_stack(tsk->stack); free_thread_stack(tsk); @@ -1862,6 +1865,7 @@ bad_fork_cleanup_count: atomic_dec(&p->cred->user->processes); exit_creds(p); bad_fork_free: + p->state = TASK_DEAD; put_task_stack(p); free_task(p); fork_out:
