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pstore: Convert buf_lock to semaphore

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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: 21b3ddd39f ("efi: Don't use spinlocks for efi vars")
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
2018-11-30 14:36:58 -08:00
parent 69596433bc
commit ea84b580b9
6 changed files with 27 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
fs/pstore/platform.c
View File

@@ -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)
/*
* 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);
#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;
}
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;
@@ -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)) {