[PATCH v2 3/3] riscv: keep booting if KFENCE pool reservation fails

[Jackie Liu]

From: Jackie Liu <liuyun01 at kylinos.cn>

A failed KFENCE pool reservation hits BUG_ON() and stops boot. Continue
building the linear map and disable KFENCE if the reservation fails.

Reject later pool initialization as well, since a replacement pool may
have huge-page mappings that kfence_protect_page() cannot handle.

Reported-by: Sashiko <sashiko-bot at kernel.org>
Closes: https://sashiko.dev/#/patchset/cover.1793017073.git.liuyun01@kylinos.cn?part=3
Reported-by: kernel test robot <lkp at intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202610290904.wbrEL97y-lkp@intel.com/
Fixes: 25abe0db9243 ("riscv: Fix kfence now that the linear mapping can be backed by PUD/P4D/PGD")
Cc: stable at vger.kernel.org
Signed-off-by: Jackie Liu <liuyun01 at kylinos.cn>
---
 arch/riscv/include/asm/kfence.h |  4 +++-
 arch/riscv/mm/init.c            | 18 ++++++++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/include/asm/kfence.h b/arch/riscv/include/asm/kfence.h
index 29cb3a6ee113..57e57426a7d6 100644
--- a/arch/riscv/include/asm/kfence.h
+++ b/arch/riscv/include/asm/kfence.h
@@ -9,9 +9,11 @@
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 
+extern bool kfence_disabled;
+
 static inline bool arch_kfence_init_pool(void)
 {
-	return true;
+	return !kfence_disabled;
 }
 
 static inline bool kfence_protect_page(unsigned long addr, bool protect)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fb37b0b67efe..d21be990346c 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -44,6 +44,10 @@ DECLARE_BITMAP(new_valid_map_cpus, NR_CPUS);
 struct kernel_mapping kernel_map __ro_after_init;
 EXPORT_SYMBOL(kernel_map);
 
+#ifdef CONFIG_KFENCE
+bool kfence_disabled __ro_after_init;
+#endif
+
 #ifdef CONFIG_64BIT
 u64 satp_mode __ro_after_init = SATP_MODE_57;
 #else
@@ -1229,10 +1233,13 @@ static void __init create_linear_mapping_page_table(void)
 	 *  for this region.
 	 */
 	kfence_pool = memblock_phys_alloc(KFENCE_POOL_SIZE, PAGE_SIZE);
-	BUG_ON(!kfence_pool);
-
-	memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE);
-	__kfence_pool = __va(kfence_pool);
+	if (kfence_pool) {
+		memblock_mark_nomap(kfence_pool, KFENCE_POOL_SIZE);
+		__kfence_pool = __va(kfence_pool);
+	} else {
+		pr_err("failed to allocate kfence pool\n");
+		kfence_disabled = true;
+	}
 #endif
 
 	/* Map all memory banks in the linear mapping */
@@ -1253,6 +1260,9 @@ static void __init create_linear_mapping_page_table(void)
 #endif
 
 #ifdef CONFIG_KFENCE
+	if (!kfence_pool)
+		return;
+
 	create_linear_mapping_range(kfence_pool, kfence_pool + KFENCE_POOL_SIZE, PAGE_SIZE, NULL);
 
 	memblock_clear_nomap(kfence_pool, KFENCE_POOL_SIZE);
-- 
2.56.0