[PATCH v6 37/44] x86: kmsan: sync metadata pages on page fault

Alexander Potapenko
2022-09-05T12:32:40Z

KMSAN assumes shadow and origin pages for every allocated page are
accessible. For pages between [VMALLOC_START, VMALLOC_END] those metadata
pages start at KMSAN_VMALLOC_SHADOW_START and
KMSAN_VMALLOC_ORIGIN_START, therefore we must sync a bigger memory
region.

Signed-off-by: Alexander Potapenko <glider@google.com>

---

v2:
-- addressed reports from kernel test robot <lkp@intel.com>

Link: https://linux-review.googlesource.com/id/Ia5bd541e54f1ecc11b86666c3ec87c62ac0bdfb8
---
arch/x86/mm/fault.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fa71a5d12e872..d728791be8ace 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -260,7 +260,7 @@ static noinline int vmalloc_fault(unsigned long address)
}
NOKPROBE_SYMBOL(vmalloc_fault);

-void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+static void __arch_sync_kernel_mappings(unsigned long start, unsigned long end)
{
unsigned long addr;

@@ -284,6 +284,27 @@ void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
}
}

+void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+{
+ __arch_sync_kernel_mappings(start, end);
+#ifdef CONFIG_KMSAN
+ /*
+ * KMSAN maintains two additional metadata page mappings for the
+ * [VMALLOC_START, VMALLOC_END) range. These mappings start at
+ * KMSAN_VMALLOC_SHADOW_START and KMSAN_VMALLOC_ORIGIN_START and
+ * have to be synced together with the vmalloc memory mapping.
+ */
+ if (start >= VMALLOC_START && end < VMALLOC_END) {
+ __arch_sync_kernel_mappings(
+ start - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START,
+ end - VMALLOC_START + KMSAN_VMALLOC_SHADOW_START);
+ __arch_sync_kernel_mappings(
+ start - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START,
+ end - VMALLOC_START + KMSAN_VMALLOC_ORIGIN_START);
+ }
+#endif
+}
+
static bool low_pfn(unsigned long pfn)
{
return pfn < max_low_pfn;
--
2.37.2.789.g6183377224-goog