x86/unwind: Prevent false warnings for non-current tasks
authorJosh Poimboeuf <jpoimboe@redhat.com>
Sat, 25 Apr 2020 10:03:06 +0000 (05:03 -0500)
committerIngo Molnar <mingo@kernel.org>
Sat, 25 Apr 2020 10:22:28 +0000 (12:22 +0200)
There's some daring kernel code out there which dumps the stack of
another task without first making sure the task is inactive.  If the
task happens to be running while the unwinder is reading the stack,
unusual unwinder warnings can result.

There's no race-free way for the unwinder to know whether such a warning
is legitimate, so just disable unwinder warnings for all non-current
tasks.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Jones <dsj@fb.com>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lore.kernel.org/r/ec424a2aea1d461eb30cab48a28c6433de2ab784.1587808742.git.jpoimboe@redhat.com
arch/x86/kernel/dumpstack_64.c
arch/x86/kernel/unwind_frame.c
arch/x86/kernel/unwind_orc.c

index 87b97897a881035966bbef4693df91e8d46b547e..460ae7f66818c7505c5c3aaf3f1be37284e2cd6c 100644 (file)
@@ -183,7 +183,8 @@ recursion_check:
         */
        if (visit_mask) {
                if (*visit_mask & (1UL << info->type)) {
-                       printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
+                       if (task == current)
+                               printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n", info->type);
                        goto unknown;
                }
                *visit_mask |= 1UL << info->type;
index a224b5ab103fa60ddd64e0a9a459c53fdb521d77..54226110bc7fd707c56c8d5715b3e776a8586c21 100644 (file)
@@ -344,6 +344,9 @@ bad_address:
        if (IS_ENABLED(CONFIG_X86_32))
                goto the_end;
 
+       if (state->task != current)
+               goto the_end;
+
        if (state->regs) {
                printk_deferred_once(KERN_WARNING
                        "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
index 64889da666f4cf52909293063ee6373c4ed79d68..45166fd50be34b61e5ee6b3fbaba61efbe4f77c4 100644 (file)
@@ -8,7 +8,13 @@
 #include <asm/orc_lookup.h>
 
 #define orc_warn(fmt, ...) \
-       printk_deferred_once(KERN_WARNING pr_fmt("WARNING: " fmt), ##__VA_ARGS__)
+       printk_deferred_once(KERN_WARNING "WARNING: " fmt, ##__VA_ARGS__)
+
+#define orc_warn_current(args...)                                      \
+({                                                                     \
+       if (state->task == current)                                     \
+               orc_warn(args);                                         \
+})
 
 extern int __start_orc_unwind_ip[];
 extern int __stop_orc_unwind_ip[];
@@ -446,8 +452,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_REG_R10:
                if (!state->regs || !state->full_regs) {
-                       orc_warn("missing regs for base reg R10 at ip %pB\n",
-                                (void *)state->ip);
+                       orc_warn_current("missing R10 value at %pB\n",
+                                        (void *)state->ip);
                        goto err;
                }
                sp = state->regs->r10;
@@ -455,8 +461,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_REG_R13:
                if (!state->regs || !state->full_regs) {
-                       orc_warn("missing regs for base reg R13 at ip %pB\n",
-                                (void *)state->ip);
+                       orc_warn_current("missing R13 value at %pB\n",
+                                        (void *)state->ip);
                        goto err;
                }
                sp = state->regs->r13;
@@ -464,8 +470,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_REG_DI:
                if (!state->regs || !state->full_regs) {
-                       orc_warn("missing regs for base reg DI at ip %pB\n",
-                                (void *)state->ip);
+                       orc_warn_current("missing RDI value at %pB\n",
+                                        (void *)state->ip);
                        goto err;
                }
                sp = state->regs->di;
@@ -473,15 +479,15 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_REG_DX:
                if (!state->regs || !state->full_regs) {
-                       orc_warn("missing regs for base reg DX at ip %pB\n",
-                                (void *)state->ip);
+                       orc_warn_current("missing DX value at %pB\n",
+                                        (void *)state->ip);
                        goto err;
                }
                sp = state->regs->dx;
                break;
 
        default:
-               orc_warn("unknown SP base reg %d for ip %pB\n",
+               orc_warn("unknown SP base reg %d at %pB\n",
                         orc->sp_reg, (void *)state->ip);
                goto err;
        }
@@ -509,8 +515,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_TYPE_REGS:
                if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
-                       orc_warn("can't dereference registers at %p for ip %pB\n",
-                                (void *)sp, (void *)orig_ip);
+                       orc_warn_current("can't access registers at %pB\n",
+                                        (void *)orig_ip);
                        goto err;
                }
 
@@ -521,8 +527,8 @@ bool unwind_next_frame(struct unwind_state *state)
 
        case ORC_TYPE_REGS_IRET:
                if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
-                       orc_warn("can't dereference iret registers at %p for ip %pB\n",
-                                (void *)sp, (void *)orig_ip);
+                       orc_warn_current("can't access iret registers at %pB\n",
+                                        (void *)orig_ip);
                        goto err;
                }
 
@@ -532,7 +538,7 @@ bool unwind_next_frame(struct unwind_state *state)
                break;
 
        default:
-               orc_warn("unknown .orc_unwind entry type %d for ip %pB\n",
+               orc_warn("unknown .orc_unwind entry type %d at %pB\n",
                         orc->type, (void *)orig_ip);
                break;
        }
@@ -564,8 +570,8 @@ bool unwind_next_frame(struct unwind_state *state)
        if (state->stack_info.type == prev_type &&
            on_stack(&state->stack_info, (void *)state->sp, sizeof(long)) &&
            state->sp <= prev_sp) {
-               orc_warn("stack going in the wrong direction? ip=%pB\n",
-                        (void *)orig_ip);
+               orc_warn_current("stack going in the wrong direction? at %pB\n",
+                                (void *)orig_ip);
                goto err;
        }