> Action Required memory error should happen only when a processor is
> about to access to a corrupted memory, so it's synchronous and only
> affects current process/thread. Recently commit 872e9a205c84 ("mm,
> memory_failure: don't send BUS_MCEERR_AO for action required error")
> fixed the issue that Action Required memory could unnecessarily send
> SIGBUS to the processes which share the error memory. But we still have
> another issue that we could send SIGBUS to a wrong thread.
>
> This is because collect_procs() and task_early_kill() fails to add the
> current process to "to-kill" list. So this patch is suggesting to fix
> it. With this fix, SIGBUS(BUS_MCEERR_AR) is never sent to non-current
> process/thread.
>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> ---
> mm/memory-failure.c | 23 ++++++++++++++++-------
> 1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git v5.7/mm/memory-failure.c v5.7_patched/mm/memory-failure.c
> index 339c07d..fa4f9cd 100644
> --- v5.7/mm/memory-failure.c
> +++ v5.7_patched/mm/memory-failure.c
> @@ -212,15 +212,13 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
> short addr_lsb = tk->size_shift;
> int ret = 0;
>
> - if ((t->mm == current->mm) || !(flags & MF_ACTION_REQUIRED))
> - pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> + pr_err("Memory failure: %#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> pfn, t->comm, t->pid);
>
> if (flags & MF_ACTION_REQUIRED) {
> - if (t->mm == current->mm)
> - ret = force_sig_mceerr(BUS_MCEERR_AR,
> + WARN_ON_ONCE(t != current);
> + ret = force_sig_mceerr(BUS_MCEERR_AR,
> (void __user *)tk->addr, addr_lsb);
> - /* send no signal to non-current processes */
> } else {
> /*
> * Don't use force here, it's convenient if the signal
> @@ -419,14 +417,25 @@ static struct task_struct *find_early_kill_thread(struct task_struct *tsk)
> * to be signaled when some page under the process is hwpoisoned.
> * Return task_struct of the dedicated thread (main thread unless explicitly
> * specified) if the process is "early kill," and otherwise returns NULL.
> + *
> + * Note that the above is true for Action Optional case, but not for Action
> + * Required case where SIGBUS should sent only to the current thread.
> */
> static struct task_struct *task_early_kill(struct task_struct *tsk,
> int force_early)
> {
> if (!tsk->mm)
> return NULL;
> - if (force_early)
> - return tsk;
> + if (force_early) {
> + /*
> + * Comparing ->mm here because current task might represent
> + * a subthread, while tsk always points to the main thread.
> + */
> + if (tsk->mm == current->mm)
> + return current;
> + else
> + return NULL;
> + }
> return find_early_kill_thread(tsk);
> }
>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
