From: Shuai Xue Date: Mon, 14 Jul 2025 11:42:12 +0000 (+0800) Subject: ACPI: APEI: handle synchronous exceptions in task work X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c1f1fda141373d7253b4c1497043b0ef85f534ce;p=thirdparty%2Flinux.git ACPI: APEI: handle synchronous exceptions in task work 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 Tested-by: Ma Wupeng Reviewed-by: Kefeng Wang Reviewed-by: Xiaofei Tan Reviewed-by: Baolin Wang Reviewed-by: Jarkko Sakkinen Reviewed-by: Jonathan Cameron Reviewed-by: Jane Chu Reviewed-by: Yazen Ghannam Reviewed-by: Hanjun Guo Link: https://patch.msgid.link/20250714114212.31660-3-xueshuai@linux.alibaba.com [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki --- diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index bda33a0f0a013..a0d54993edb3b 100644 --- a/drivers/acpi/apei/ghes.c +++ b/drivers/acpi/apei/ghes.c @@ -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)) { diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h index be1dd4c1a9174..ebd21b05fe6ed 100644 --- a/include/acpi/ghes.h +++ b/include/acpi/ghes.h @@ -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 { diff --git a/include/linux/mm.h b/include/linux/mm.h index 0ef2ba0c667af..02dffff2508bc 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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); diff --git a/mm/memory-failure.c b/mm/memory-failure.c index b91a33fb6c694..5278132a2b6d9 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -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;