From: Kees Cook keescook@chromium.org
commit ea84b580b95521644429cc6748b6c2bf27c8b0f3 upstream.
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: Sebastian Andrzej Siewior bigeasy@linutronix.de Fixes: 21b3ddd39fee ("efi: Don't use spinlocks for efi vars") Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kernel/nvram_64.c | 2 - drivers/acpi/apei/erst.c | 1 drivers/firmware/efi/efi-pstore.c | 4 --- fs/pstore/platform.c | 44 +++++++++++++++++++------------------- fs/pstore/ram.c | 1 include/linux/pstore.h | 7 ++---- 6 files changed, 27 insertions(+), 32 deletions(-)
--- a/arch/powerpc/kernel/nvram_64.c +++ b/arch/powerpc/kernel/nvram_64.c @@ -566,8 +566,6 @@ 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 */ --- a/drivers/acpi/apei/erst.c +++ b/drivers/acpi/apei/erst.c @@ -1175,7 +1175,6 @@ 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 - --- a/drivers/firmware/efi/efi-pstore.c +++ b/drivers/firmware/efi/efi-pstore.c @@ -258,8 +258,7 @@ static int efi_pstore_write(struct pstor 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(); @@ -368,7 +367,6 @@ static __init int efivars_pstore_init(vo 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); --- a/fs/pstore/platform.c +++ b/fs/pstore/platform.c @@ -129,26 +129,27 @@ static const char *get_reason_str(enum k } }
-bool pstore_cannot_block_path(enum kmsg_dump_reason 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 case of NMI path, pstore shouldn't be blocked - * regardless of 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);
#ifdef CONFIG_PSTORE_ZLIB_COMPRESS /* Derived from logfs_compress() */ @@ -499,23 +500,23 @@ static void pstore_dump(struct kmsg_dump 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; + } + if (down_interruptible(&psinfo->buf_lock)) { + pr_err("could not grab semaphore?!\n"); return; } - } else { - spin_lock_irqsave(&psinfo->buf_lock, flags); - is_locked = 1; } + oopscount++; while (total < kmsg_bytes) { char *dst; @@ -532,7 +533,7 @@ static void pstore_dump(struct kmsg_dump 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 { @@ -550,7 +551,7 @@ static void pstore_dump(struct kmsg_dump 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); @@ -573,8 +574,8 @@ static void pstore_dump(struct kmsg_dump total += record.size; part++; } - if (is_locked) - spin_unlock_irqrestore(&psinfo->buf_lock, flags); + + up(&psinfo->buf_lock); }
static struct kmsg_dumper pstore_dumper = { @@ -693,6 +694,7 @@ int pstore_register(struct pstore_info * 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)) { --- a/fs/pstore/ram.c +++ b/fs/pstore/ram.c @@ -812,7 +812,6 @@ static int ramoops_probe(struct platform err = -ENOMEM; goto fail_clear; } - spin_lock_init(&cxt->pstore.buf_lock);
cxt->pstore.flags = PSTORE_FLAGS_DMESG; if (cxt->console_size) --- a/include/linux/pstore.h +++ b/include/linux/pstore.h @@ -26,7 +26,7 @@ #include <linux/errno.h> #include <linux/kmsg_dump.h> #include <linux/mutex.h> -#include <linux/spinlock.h> +#include <linux/semaphore.h> #include <linux/time.h> #include <linux/types.h>
@@ -88,7 +88,7 @@ struct pstore_record { * @owner: module which is repsonsible for this backend driver * @name: name of the backend driver * - * @buf_lock: spinlock to serialize access to @buf + * @buf_lock: semaphore to serialize access to @buf * @buf: preallocated crash dump buffer * @bufsize: size of @buf available for crash dump bytes (must match * smallest number of bytes available for writing to a @@ -173,7 +173,7 @@ struct pstore_info { struct module *owner; char *name;
- spinlock_t buf_lock; + struct semaphore buf_lock; char *buf; size_t bufsize;
@@ -199,7 +199,6 @@ struct pstore_info {
extern int pstore_register(struct pstore_info *); extern void pstore_unregister(struct pstore_info *); -extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
struct pstore_ftrace_record { unsigned long ip;