Commit 405c0759 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

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: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f29119c783a9680a4b4656e751b6123917ace94b.1477926663.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0c183d92
...@@ -315,6 +315,9 @@ static void account_kernel_stack(struct task_struct *tsk, int account) ...@@ -315,6 +315,9 @@ static void account_kernel_stack(struct task_struct *tsk, int account)
static void release_task_stack(struct task_struct *tsk) 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); account_kernel_stack(tsk, -1);
arch_release_thread_stack(tsk->stack); arch_release_thread_stack(tsk->stack);
free_thread_stack(tsk); free_thread_stack(tsk);
...@@ -1862,6 +1865,7 @@ static __latent_entropy struct task_struct *copy_process( ...@@ -1862,6 +1865,7 @@ static __latent_entropy struct task_struct *copy_process(
atomic_dec(&p->cred->user->processes); atomic_dec(&p->cred->user->processes);
exit_creds(p); exit_creds(p);
bad_fork_free: bad_fork_free:
p->state = TASK_DEAD;
put_task_stack(p); put_task_stack(p);
free_task(p); free_task(p);
fork_out: fork_out:
......
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