7 files changed, 55 insertions, 10 deletions

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 7f2eed1fc81b..6461a16b4559 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -407,6 +407,13 @@ void hyperv_cleanup(void)
         /* Reset our OS id */
         wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
 
+        /*
+         * Reset hypercall page reference before reset the page,
+         * let hypercall operations fail safely rather than
+         * panic the kernel for using invalid hypercall page
+         */
+        hv_hypercall_pg = NULL;
+
         /* Reset the hypercall page */
         hypercall_msr.as_uint64 = 0;
         wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 0ce558a8150d..8f657286d599 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -7,11 +7,7 @@
 #endif
 
 #ifdef CONFIG_KASAN
-#ifdef CONFIG_KASAN_EXTRA
-#define KASAN_STACK_ORDER 2
-#else
 #define KASAN_STACK_ORDER 1
-#endif
 #else
 #define KASAN_STACK_ORDER 0
 #endif
diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 1f86e1b0a5cd..499578f7e6d7 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -23,6 +23,12 @@ struct unwind_state {
 #elif defined(CONFIG_UNWINDER_FRAME_POINTER)
         bool got_irq;
         unsigned long *bp, *orig_sp, ip;
+        /*
+         * If non-NULL: The current frame is incomplete and doesn't contain a
+         * valid BP. When looking for the next frame, use this instead of the
+         * non-existent saved BP.
+         */
+        unsigned long *next_bp;
         struct pt_regs *regs;
 #else
         unsigned long *sp;
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 3dc26f95d46e..9b9fd4826e7a 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -320,10 +320,14 @@ bool unwind_next_frame(struct unwind_state *state)
         }
 
         /* Get the next frame pointer: */
-        if (state->regs)
+        if (state->next_bp) {
+                next_bp = state->next_bp;
+                state->next_bp = NULL;
+        } else if (state->regs) {
                 next_bp = (unsigned long *)state->regs->bp;
-        else
+        } else {
                 next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task, *state->bp);
+        }
 
         /* Move to the next frame if it's safe: */
         if (!update_stack_state(state, next_bp))
@@ -398,6 +402,21 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
 
         bp = get_frame_pointer(task, regs);
 
+        /*
+         * If we crash with IP==0, the last successfully executed instruction
+         * was probably an indirect function call with a NULL function pointer.
+         * That means that SP points into the middle of an incomplete frame:
+         * *SP is a return pointer, and *(SP-sizeof(unsigned long)) is where we
+         * would have written a frame pointer if we hadn't crashed.
+         * Pretend that the frame is complete and that BP points to it, but save
+         * the real BP so that we can use it when looking for the next frame.
+         */
+        if (regs && regs->ip == 0 &&
+            (unsigned long *)kernel_stack_pointer(regs) >= first_frame) {
+                state->next_bp = bp;
+                bp = ((unsigned long *)kernel_stack_pointer(regs)) - 1;
+        }
+
         /* Initialize stack info and make sure the frame data is accessible: */
         get_stack_info(bp, state->task, &state->stack_info,
                        &state->stack_mask);
@@ -410,7 +429,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
          */
         while (!unwind_done(state) &&
                (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
-                        state->bp < first_frame))
+                        (state->next_bp == NULL && state->bp < first_frame)))
                 unwind_next_frame(state);
 }
 EXPORT_SYMBOL_GPL(__unwind_start);
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 26038eacf74a..89be1be1790c 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -113,6 +113,20 @@ static struct orc_entry *orc_ftrace_find(unsigned long ip)
 }
 #endif
 
+/*
+ * If we crash with IP==0, the last successfully executed instruction
+ * was probably an indirect function call with a NULL function pointer,
+ * and we don't have unwind information for NULL.
+ * This hardcoded ORC entry for IP==0 allows us to unwind from a NULL function
+ * pointer into its parent and then continue normally from there.
+ */
+static struct orc_entry null_orc_entry = {
+        .sp_offset = sizeof(long),
+        .sp_reg = ORC_REG_SP,
+        .bp_reg = ORC_REG_UNDEFINED,
+        .type = ORC_TYPE_CALL
+};
+
 static struct orc_entry *orc_find(unsigned long ip)
 {
         static struct orc_entry *orc;
@@ -120,6 +134,9 @@ static struct orc_entry *orc_find(unsigned long ip)
         if (!orc_init)
                 return NULL;
 
+        if (ip == 0)
+                return &null_orc_entry;
+
         /* For non-init vmlinux addresses, use the fast lookup table: */
         if (ip >= LOOKUP_START_IP && ip < LOOKUP_STOP_IP) {
                 unsigned int idx, start, stop;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 14e6119838a6..4c570612e24e 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -738,7 +738,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
 {
         unsigned long numpages, pmask, psize, lpaddr, pfn, old_pfn;
         pgprot_t old_prot, new_prot, req_prot, chk_prot;
-        pte_t new_pte, old_pte, *tmp;
+        pte_t new_pte, *tmp;
         enum pg_level level;
 
         /*
@@ -781,7 +781,7 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
          * Convert protection attributes to 4k-format, as cpa->mask* are set
          * up accordingly.
          */
-        old_pte = *kpte;
+
         /* Clear PSE (aka _PAGE_PAT) and move PAT bit to correct position */
         req_prot = pgprot_large_2_4k(old_prot);
 
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3d7a6a9c2370..f8f6f04c4453 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -733,7 +733,7 @@
                 KEEP(*(.orc_unwind_ip))                                 \
                 __stop_orc_unwind_ip = .;                               \
         }                                                               \
-        . = ALIGN(6);                                                   \
+        . = ALIGN(2);                                                   \
         .orc_unwind : AT(ADDR(.orc_unwind) - LOAD_OFFSET) {             \
                 __start_orc_unwind = .;                                 \
                 KEEP(*(.orc_unwind))                                    \