Commit ea84b580 authored by Kees Cook's avatar Kees Cook
Browse files

pstore: Convert buf_lock to semaphore 



Instead of running with interrupts disabled, use a semaphore. This should
make it easier for backends that may need to sleep (e.g. EFI) when
performing a write:

|BUG: sleeping function called from invalid context at kernel/sched/completion.c:99
|in_atomic(): 1, irqs_disabled(): 1, pid: 2236, name: sig-xstate-bum
|Preemption disabled at:
|[<ffffffff99d60512>] pstore_dump+0x72/0x330
|CPU: 26 PID: 2236 Comm: sig-xstate-bum Tainted: G      D           4.20.0-rc3 #45
|Call Trace:
| dump_stack+0x4f/0x6a
| ___might_sleep.cold.91+0xd3/0xe4
| __might_sleep+0x50/0x90
| wait_for_completion+0x32/0x130
| virt_efi_query_variable_info+0x14e/0x160
| efi_query_variable_store+0x51/0x1a0
| efivar_entry_set_safe+0xa3/0x1b0
| efi_pstore_write+0x109/0x140
| pstore_dump+0x11c/0x330
| kmsg_dump+0xa4/0xd0
| oops_exit+0x22/0x30
...

Reported-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Fixes: 21b3ddd3 ("efi: Don't use spinlocks for efi vars")
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 69596433

arch/powerpc/kernel/nvram_64.c

+0 −2
Original line number Diff line number Diff line
@@ -563,8 +563,6 @@ static int nvram_pstore_init(void) 
	nvram_pstore_info.buf = oops_data;

	nvram_pstore_info.bufsize = oops_data_sz;



	spin_lock_init(&nvram_pstore_info.buf_lock);



	rc = pstore_register(&nvram_pstore_info);

	if (rc && (rc != -EPERM))

		/* Print error only when pstore.backend == nvram */

drivers/acpi/apei/erst.c

+0 −1
Original line number Diff line number Diff line
@@ -1176,7 +1176,6 @@ static int __init erst_init(void) 
	"Error Record Serialization Table (ERST) support is initialized.\n");



	buf = kmalloc(erst_erange.size, GFP_KERNEL);

	spin_lock_init(&erst_info.buf_lock);

	if (buf) {

		erst_info.buf = buf + sizeof(struct cper_pstore_record);

		erst_info.bufsize = erst_erange.size -

drivers/firmware/efi/efi-pstore.c

+1 −3
Original line number Diff line number Diff line
@@ -259,8 +259,7 @@ static int efi_pstore_write(struct pstore_record *record) 
		efi_name[i] = name[i];



	ret = efivar_entry_set_safe(efi_name, vendor, PSTORE_EFI_ATTRIBUTES,

			      !pstore_cannot_block_path(record->reason),

			      record->size, record->psi->buf);

			      preemptible(), record->size, record->psi->buf);



	if (record->reason == KMSG_DUMP_OOPS)

		efivar_run_worker();
@@ -369,7 +368,6 @@ static __init int efivars_pstore_init(void) 
		return -ENOMEM;



	efi_pstore_info.bufsize = 1024;

	spin_lock_init(&efi_pstore_info.buf_lock);



	if (pstore_register(&efi_pstore_info)) {

		kfree(efi_pstore_info.buf);

fs/pstore/platform.c

+23 −21
Original line number Diff line number Diff line
@@ -161,26 +161,27 @@ static const char *get_reason_str(enum kmsg_dump_reason reason) 
	}

}



bool pstore_cannot_block_path(enum kmsg_dump_reason reason)

{

/*

	 * In case of NMI path, pstore shouldn't be blocked

	 * regardless of reason.

 * Should pstore_dump() wait for a concurrent pstore_dump()? If

 * not, the current pstore_dump() will report a failure to dump

 * and return.

 */

static bool pstore_cannot_wait(enum kmsg_dump_reason reason)

{

	/* In NMI path, pstore shouldn't block regardless of reason. */

	if (in_nmi())

		return true;



	switch (reason) {

	/* In panic case, other cpus are stopped by smp_send_stop(). */

	case KMSG_DUMP_PANIC:

	/* Emergency restart shouldn't be blocked by spin lock. */

	/* Emergency restart shouldn't be blocked. */

	case KMSG_DUMP_EMERG:

		return true;

	default:

		return false;

	}

}

EXPORT_SYMBOL_GPL(pstore_cannot_block_path);



#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)

static int zbufsize_deflate(size_t size)
@@ -400,23 +401,23 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
	unsigned long	total = 0;

	const char	*why;

	unsigned int	part = 1;

	unsigned long	flags = 0;

	int		is_locked;

	int		ret;



	why = get_reason_str(reason);



	if (pstore_cannot_block_path(reason)) {

		is_locked = spin_trylock_irqsave(&psinfo->buf_lock, flags);

		if (!is_locked) {

			pr_err("pstore dump routine blocked in %s path, may corrupt error record\n"

				       , in_nmi() ? "NMI" : why);

	if (down_trylock(&psinfo->buf_lock)) {

		/* Failed to acquire lock: give up if we cannot wait. */

		if (pstore_cannot_wait(reason)) {

			pr_err("dump skipped in %s path: may corrupt error record\n",

				in_nmi() ? "NMI" : why);

			return;

		}

	} else {

		spin_lock_irqsave(&psinfo->buf_lock, flags);

		is_locked = 1;

		if (down_interruptible(&psinfo->buf_lock)) {

			pr_err("could not grab semaphore?!\n");

			return;

		}

	}



	oopscount++;

	while (total < kmsg_bytes) {

		char *dst;
@@ -433,7 +434,7 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
		record.part = part;

		record.buf = psinfo->buf;



		if (big_oops_buf && is_locked) {

		if (big_oops_buf) {

			dst = big_oops_buf;

			dst_size = big_oops_buf_sz;

		} else {
@@ -451,7 +452,7 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
					  dst_size, &dump_size))

			break;



		if (big_oops_buf && is_locked) {

		if (big_oops_buf) {

			zipped_len = pstore_compress(dst, psinfo->buf,

						header_size + dump_size,

						psinfo->bufsize);
@@ -474,8 +475,8 @@ static void pstore_dump(struct kmsg_dumper *dumper, 
		total += record.size;

		part++;

	}

	if (is_locked)

		spin_unlock_irqrestore(&psinfo->buf_lock, flags);



	up(&psinfo->buf_lock);

}



static struct kmsg_dumper pstore_dumper = {
@@ -594,6 +595,7 @@ int pstore_register(struct pstore_info *psi) 
		psi->write_user = pstore_write_user_compat;

	psinfo = psi;

	mutex_init(&psinfo->read_mutex);

	sema_init(&psinfo->buf_lock, 1);

	spin_unlock(&pstore_lock);



	if (owner && !try_module_get(owner)) {

fs/pstore/ram.c

+0 −1
Original line number Diff line number Diff line
@@ -815,7 +815,6 @@ static int ramoops_probe(struct platform_device *pdev) 
		err = -ENOMEM;

		goto fail_clear;

	}

	spin_lock_init(&cxt->pstore.buf_lock);



	cxt->pstore.flags = PSTORE_FLAGS_DMESG;

	if (cxt->console_size)

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