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authorAndy Lutomirski <[email protected]>2016-10-31 08:11:43 -0700
committerIngo Molnar <[email protected]>2016-11-01 07:39:17 +0100
commit405c0759712f57b680f66aee9c55cd06ad1cbdef (patch)
tree3a93cb428043131fd231b348dbe469be9dfadc30
parent0c183d92b20b5c84ca655b45ef57b3318b83eb9e (diff)
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.luto@kernel.org Signed-off-by: Ingo Molnar <[email protected]>
-rw-r--r--kernel/fork.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 623259fc794d..997ac1d584f7 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: