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ACPI: APEI: handle synchronous exceptions in task work

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The memory uncorrected error could be signaled by asynchronous interrupt
(specifically, SPI in arm64 platform), e.g. when an error is detected by
a background scrubber, or signaled by synchronous exception
(specifically, data abort exception in arm64 platform), e.g. when a CPU
tries to access a poisoned cache line. Currently, both synchronous and
asynchronous errors use memory_failure_queue() to schedule
memory_failure() to exectute in a kworker context.

As a result, when a user-space process is accessing a poisoned data, a
data abort is taken and the memory_failure() is executed in the kworker
context, which:

  - will send wrong si_code by SIGBUS signal in early_kill mode, and
  - can not kill the user-space in some cases resulting a synchronous
    error infinite loop

Issue 1: send wrong si_code in early_kill mode

Since commit a70297d22132 ("ACPI: APEI: set memory failure flags as
MF_ACTION_REQUIRED on synchronous events")', the flag MF_ACTION_REQUIRED
could be used to determine whether a synchronous exception occurs on
ARM64 platform.  When a synchronous exception is detected, the kernel is
expected to terminate the current process which has accessed a poisoned
page. This is done by sending a SIGBUS signal with error code
BUS_MCEERR_AR, indicating an action-required machine check error on
read.

However, when kill_proc() is called to terminate the processes who has
the poisoned page mapped, it sends the incorrect SIGBUS error code
BUS_MCEERR_AO because the context in which it operates is not the one
where the error was triggered.

To reproduce this problem:

  #sysctl -w vm.memory_failure_early_kill=1
  vm.memory_failure_early_kill = 1

  # STEP2: inject an UCE error and consume it to trigger a synchronous error
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 5 addr 0xffffb0d75000
  page not present
  Test passed

The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO
error and it is not factually correct.

After this change:

  # STEP1: enable early kill mode
  #sysctl -w vm.memory_failure_early_kill=1
  vm.memory_failure_early_kill = 1
  # STEP2: inject an UCE error and consume it to trigger a synchronous error
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 4 addr 0xffffb0d75000
  page not present
  Test passed

The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR
error as expected.

Issue 2: a synchronous error infinite loop

If a user-space process, e.g. devmem, accesses a poisoned page for which
the HWPoison flag is set, kill_accessing_process() is called to send
SIGBUS to current processs with error info. Since the memory_failure()
is executed in the kworker context, it will just do nothing but return
EFAULT. So, devmem will access the posioned page and trigger an
exception again, resulting in a synchronous error infinite loop. Such
exception loop may cause platform firmware to exceed some threshold and
reboot when Linux could have recovered from this error.

To reproduce this problem:

  # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 4 addr 0xffffb0d75000
  page not present
  Test passed

  # STEP 2: access the same page and it will trigger a synchronous error infinite loop
  devmem 0x4092d55b400

To fix above two issues, queue memory_failure() as a task_work so that
it runs in the context of the process that is actually consuming the
poisoned data.

Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Tested-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://patch.msgid.link/20250714114212.31660-3-xueshuai@linux.alibaba.com
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Shuai Xue 2025-07-14 19:42:12 +08:00 committed by Rafael J. Wysocki
parent 79a5ae3c4c
commit c1f1fda141
4 changed files with 45 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
drivers/acpi/apei/ghes.c
View File

@ -464,28 +464,41 @@ static void ghes_clear_estatus(struct ghes *ghes,
ghes_ack_error(ghes->generic_v2);
}
/*
* Called as task_work before returning to user-space.
* Ensure any queued work has been done before we return to the context that
* triggered the notification.
/**
* struct ghes_task_work - for synchronous RAS event
*
* @twork: callback_head for task work
* @pfn: page frame number of corrupted page
* @flags: work control flags
*
* Structure to pass task work to be handled before
* returning to user-space via task_work_add().
*/
static void ghes_kick_task_work(struct callback_head *head)
struct ghes_task_work {
struct callback_head twork;
u64 pfn;
int flags;
};
static void memory_failure_cb(struct callback_head *twork)
{
struct acpi_hest_generic_status *estatus;
struct ghes_estatus_node *estatus_node;
u32 node_len;
struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork);
int ret;
estatus_node = container_of(head, struct ghes_estatus_node, task_work);
if (IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))
memory_failure_queue_kick(estatus_node->task_work_cpu);
ret = memory_failure(twcb->pfn, twcb->flags);
gen_pool_free(ghes_estatus_pool, (unsigned long)twcb, sizeof(*twcb));
estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
node_len = GHES_ESTATUS_NODE_LEN(cper_estatus_len(estatus));
gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, node_len);
if (!ret || ret == -EHWPOISON || ret == -EOPNOTSUPP)
return;
pr_err("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
twcb->pfn, current->comm, task_pid_nr(current));
force_sig(SIGBUS);
}
static bool ghes_do_memory_failure(u64 physical_addr, int flags)
{
struct ghes_task_work *twcb;
unsigned long pfn;
if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))
@ -499,6 +512,18 @@ static bool ghes_do_memory_failure(u64 physical_addr, int flags)
return false;
}
if (flags == MF_ACTION_REQUIRED && current->mm) {
twcb = (void *)gen_pool_alloc(ghes_estatus_pool, sizeof(*twcb));
if (!twcb)
return false;
twcb->pfn = pfn;
twcb->flags = flags;
init_task_work(&twcb->twork, memory_failure_cb);
task_work_add(current, &twcb->twork, TWA_RESUME);
return true;
}
memory_failure_queue(pfn, flags);
return true;
}
@ -842,7 +867,7 @@ int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd)
}
EXPORT_SYMBOL_NS_GPL(cxl_cper_kfifo_get, "CXL");
static bool ghes_do_proc(struct ghes *ghes,
static void ghes_do_proc(struct ghes *ghes,
const struct acpi_hest_generic_status *estatus)
{
int sev, sec_sev;
@ -912,8 +937,6 @@ static bool ghes_do_proc(struct ghes *ghes,
current->comm, task_pid_nr(current));
force_sig(SIGBUS);
}
return queued;
}
static void __ghes_print_estatus(const char *pfx,
@ -1219,9 +1242,7 @@ static void ghes_proc_in_irq(struct irq_work *irq_work)
struct ghes_estatus_node *estatus_node;
struct acpi_hest_generic *generic;
struct acpi_hest_generic_status *estatus;
bool task_work_pending;
u32 len, node_len;
int ret;
llnode = llist_del_all(&ghes_estatus_llist);
/*
@ -1236,25 +1257,16 @@ static void ghes_proc_in_irq(struct irq_work *irq_work)
estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
len = cper_estatus_len(estatus);
node_len = GHES_ESTATUS_NODE_LEN(len);
task_work_pending = ghes_do_proc(estatus_node->ghes, estatus);
ghes_do_proc(estatus_node->ghes, estatus);
if (!ghes_estatus_cached(estatus)) {
generic = estatus_node->generic;
if (ghes_print_estatus(NULL, generic, estatus))
ghes_estatus_cache_add(generic, estatus);
}
if (task_work_pending && current->mm) {
estatus_node->task_work.func = ghes_kick_task_work;
estatus_node->task_work_cpu = smp_processor_id();
ret = task_work_add(current, &estatus_node->task_work,
TWA_RESUME);
if (ret)
estatus_node->task_work.func = NULL;
}
if (!estatus_node->task_work.func)
gen_pool_free(ghes_estatus_pool,
(unsigned long)estatus_node, node_len);
gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
node_len);
llnode = next;
}
@ -1315,7 +1327,6 @@ static int ghes_in_nmi_queue_one_entry(struct ghes *ghes,
estatus_node->ghes = ghes;
estatus_node->generic = ghes->generic;
estatus_node->task_work.func = NULL;
estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
if (__ghes_read_estatus(estatus, buf_paddr, fixmap_idx, len)) {

3
include/acpi/ghes.h
View File

@ -35,9 +35,6 @@ struct ghes_estatus_node {
struct llist_node llnode;
struct acpi_hest_generic *generic;
struct ghes *ghes;
int task_work_cpu;
struct callback_head task_work;
};
struct ghes_estatus_cache {

1
include/linux/mm.h
View File

@ -3896,7 +3896,6 @@ enum mf_flags {
int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
unsigned long count, int mf_flags);
extern int memory_failure(unsigned long pfn, int flags);
extern void memory_failure_queue_kick(int cpu);
extern int unpoison_memory(unsigned long pfn);
extern atomic_long_t num_poisoned_pages __read_mostly;
extern int soft_offline_page(unsigned long pfn, int flags);

13
mm/memory-failure.c
View File

@ -2503,19 +2503,6 @@ static void memory_failure_work_func(struct work_struct *work)
}
}
/*
* Process memory_failure work queued on the specified CPU.
* Used to avoid return-to-userspace racing with the memory_failure workqueue.
*/
void memory_failure_queue_kick(int cpu)
{
struct memory_failure_cpu *mf_cpu;
mf_cpu = &per_cpu(memory_failure_cpu, cpu);
cancel_work_sync(&mf_cpu->work);
memory_failure_work_func(&mf_cpu->work);
}
static int __init memory_failure_init(void)
{
struct memory_failure_cpu *mf_cpu;