pstore: replace spinlock_t by raw_spinlock_t

pstore_dump() is called when both preemption and local IRQ are disabled,
and a spinlock is obtained, which is problematic for the RT kernel because
in this configuration, spinlocks are sleep locks.

Replace the spinlock_t with raw_spinlock_t to avoid sleeping in atomic context.

Signed-off-by: Wen Yang <wen.yang@linux.dev>
Cc: Kees Cook <kees@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guilherme G. Piccoli <gpiccoli@igalia.com>
Cc: linux-hardening@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/20240819145945.61274-1-wen.yang@linux.dev
Signed-off-by: Kees Cook <kees@kernel.org>

Author: Wen Yang

fs/pstore/platform.c

@@ -288,13 +288,13 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 	why = kmsg_dump_reason_str(reason);
 
 	if (pstore_cannot_block_path(reason)) {
-		if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
+		if (!raw_spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
 			pr_err("dump skipped in %s path because of concurrent dump\n",
 					in_nmi() ? "NMI" : why);
 			return;
 		}
 	} else {
-		spin_lock_irqsave(&psinfo->buf_lock, flags);
+		raw_spin_lock_irqsave(&psinfo->buf_lock, flags);
 	}
 
 	kmsg_dump_rewind(&iter);
@@ -364,7 +364,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
 		total += record.size;
 		part++;
 	}
-	spin_unlock_irqrestore(&psinfo->buf_lock, flags);
+	raw_spin_unlock_irqrestore(&psinfo->buf_lock, flags);
 
 	if (saved_ret) {
 		pr_err_once("backend (%s) writing error (%d)\n", psinfo->name,
@@ -503,7 +503,7 @@ int pstore_register(struct pstore_info *psi)
 		psi->write_user = pstore_write_user_compat;
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
-	spin_lock_init(&psinfo->buf_lock);
+	raw_spin_lock_init(&psinfo->buf_lock);
 
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		allocate_buf_for_compression();

include/linux/pstore.h

@@ -182,7 +182,7 @@ struct pstore_info {
 	struct module	*owner;
 	const char	*name;
 
-	spinlock_t	buf_lock;
+	raw_spinlock_t	buf_lock;
 	char		*buf;
 	size_t		bufsize;