[PATCH 5.4 184/191] lib/ubsan: dont serialize UBSAN report

From: Julien Grall julien.grall@arm.com

[ Upstream commit ce5c31db3645b649a31044a4d8b6057f6c723702 ]

At the moment, UBSAN report will be serialized using a spin_lock(). On RT-systems, spinlocks are turned to rt_spin_lock and may sleep. This will result to the following splat if the undefined behavior is in a context that can sleep:

BUG: sleeping function called from invalid context at /src/linux/kernel/locking/rtmutex.c:968 in_atomic(): 1, irqs_disabled(): 128, pid: 3447, name: make 1 lock held by make/3447: #0: 000000009a966332 (&mm->mmap_sem){++++}, at: do_page_fault+0x140/0x4f8 irq event stamp: 6284 hardirqs last enabled at (6283): [<ffff000011326520>] _raw_spin_unlock_irqrestore+0x90/0xa0 hardirqs last disabled at (6284): [<ffff0000113262b0>] _raw_spin_lock_irqsave+0x30/0x78 softirqs last enabled at (2430): [<ffff000010088ef8>] fpsimd_restore_current_state+0x60/0xe8 softirqs last disabled at (2427): [<ffff000010088ec0>] fpsimd_restore_current_state+0x28/0xe8 Preemption disabled at: [<ffff000011324a4c>] rt_mutex_futex_unlock+0x4c/0xb0 CPU: 3 PID: 3447 Comm: make Tainted: G W 5.2.14-rt7-01890-ge6e057589653 #911 Call trace: dump_backtrace+0x0/0x148 show_stack+0x14/0x20 dump_stack+0xbc/0x104 ___might_sleep+0x154/0x210 rt_spin_lock+0x68/0xa0 ubsan_prologue+0x30/0x68 handle_overflow+0x64/0xe0 __ubsan_handle_add_overflow+0x10/0x18 __lock_acquire+0x1c28/0x2a28 lock_acquire+0xf0/0x370 _raw_spin_lock_irqsave+0x58/0x78 rt_mutex_futex_unlock+0x4c/0xb0 rt_spin_unlock+0x28/0x70 get_page_from_freelist+0x428/0x2b60 __alloc_pages_nodemask+0x174/0x1708 alloc_pages_vma+0x1ac/0x238 __handle_mm_fault+0x4ac/0x10b0 handle_mm_fault+0x1d8/0x3b0 do_page_fault+0x1c8/0x4f8 do_translation_fault+0xb8/0xe0 do_mem_abort+0x3c/0x98 el0_da+0x20/0x24

The spin_lock() will protect against multiple CPUs to output a report together, I guess to prevent them from being interleaved. However, they can still interleave with other messages (and even splat from __might_sleep).

So the lock usefulness seems pretty limited. Rather than trying to accomodate RT-system by switching to a raw_spin_lock(), the lock is now completely dropped.

Link: http://lkml.kernel.org/r/20190920100835.14999-1-julien.grall@arm.com Signed-off-by: Julien Grall julien.grall@arm.com Reported-by: Andre Przywara andre.przywara@arm.com Acked-by: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Steven Rostedt rostedt@goodmis.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- lib/ubsan.c | 64 +++++++++++++++++++---------------------------------- 1 file changed, 23 insertions(+), 41 deletions(-)

diff --git a/lib/ubsan.c b/lib/ubsan.c index 0c4681118fcd..f007a406f89c 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -140,25 +140,21 @@ static void val_to_string(char *str, size_t size, struct type_descriptor *type, } }

-static DEFINE_SPINLOCK(report_lock); - -static void ubsan_prologue(struct source_location *location, - unsigned long *flags) +static void ubsan_prologue(struct source_location *location) { current->in_ubsan++; - spin_lock_irqsave(&report_lock, *flags);

pr_err("========================================" "========================================\n"); print_source_location("UBSAN: Undefined behaviour in", location); }

-static void ubsan_epilogue(unsigned long *flags) +static void ubsan_epilogue(void) { dump_stack(); pr_err("========================================" "========================================\n"); - spin_unlock_irqrestore(&report_lock, *flags); + current->in_ubsan--; }

@@ -167,14 +163,13 @@ static void handle_overflow(struct overflow_data *data, void *lhs, {

struct type_descriptor *type = data->type; - unsigned long flags; char lhs_val_str[VALUE_LENGTH]; char rhs_val_str[VALUE_LENGTH];

if (suppress_report(&data->location)) return;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs); val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs); @@ -186,7 +181,7 @@ static void handle_overflow(struct overflow_data *data, void *lhs, rhs_val_str, type->type_name);

- ubsan_epilogue(&flags); + ubsan_epilogue(); }

void __ubsan_handle_add_overflow(struct overflow_data *data, @@ -214,20 +209,19 @@ EXPORT_SYMBOL(__ubsan_handle_mul_overflow); void __ubsan_handle_negate_overflow(struct overflow_data *data, void *old_val) { - unsigned long flags; char old_val_str[VALUE_LENGTH];

if (suppress_report(&data->location)) return;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);

pr_err("negation of %s cannot be represented in type %s:\n", old_val_str, data->type->type_name);

- ubsan_epilogue(&flags); + ubsan_epilogue(); } EXPORT_SYMBOL(__ubsan_handle_negate_overflow);

@@ -235,13 +229,12 @@ EXPORT_SYMBOL(__ubsan_handle_negate_overflow); void __ubsan_handle_divrem_overflow(struct overflow_data *data, void *lhs, void *rhs) { - unsigned long flags; char rhs_val_str[VALUE_LENGTH];

if (suppress_report(&data->location)) return;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);

@@ -251,58 +244,52 @@ void __ubsan_handle_divrem_overflow(struct overflow_data *data, else pr_err("division by zero\n");

- ubsan_epilogue(&flags); + ubsan_epilogue(); } EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);

static void handle_null_ptr_deref(struct type_mismatch_data_common *data) { - unsigned long flags; - if (suppress_report(data->location)) return;

- ubsan_prologue(data->location, &flags); + ubsan_prologue(data->location);

pr_err("%s null pointer of type %s\n", type_check_kinds[data->type_check_kind], data->type->type_name);

- ubsan_epilogue(&flags); + ubsan_epilogue(); }

static void handle_misaligned_access(struct type_mismatch_data_common *data, unsigned long ptr) { - unsigned long flags; - if (suppress_report(data->location)) return;

- ubsan_prologue(data->location, &flags); + ubsan_prologue(data->location);

pr_err("%s misaligned address %p for type %s\n", type_check_kinds[data->type_check_kind], (void *)ptr, data->type->type_name); pr_err("which requires %ld byte alignment\n", data->alignment);

- ubsan_epilogue(&flags); + ubsan_epilogue(); }

static void handle_object_size_mismatch(struct type_mismatch_data_common *data, unsigned long ptr) { - unsigned long flags; - if (suppress_report(data->location)) return;

- ubsan_prologue(data->location, &flags); + ubsan_prologue(data->location); pr_err("%s address %p with insufficient space\n", type_check_kinds[data->type_check_kind], (void *) ptr); pr_err("for an object of type %s\n", data->type->type_name); - ubsan_epilogue(&flags); + ubsan_epilogue(); }

static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data, @@ -351,25 +338,23 @@ EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);

void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index) { - unsigned long flags; char index_str[VALUE_LENGTH];

if (suppress_report(&data->location)) return;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(index_str, sizeof(index_str), data->index_type, index); pr_err("index %s is out of range for type %s\n", index_str, data->array_type->type_name); - ubsan_epilogue(&flags); + ubsan_epilogue(); } EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);

void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, void *lhs, void *rhs) { - unsigned long flags; struct type_descriptor *rhs_type = data->rhs_type; struct type_descriptor *lhs_type = data->lhs_type; char rhs_str[VALUE_LENGTH]; @@ -379,7 +364,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, if (suppress_report(&data->location)) goto out;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs); val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs); @@ -402,7 +387,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, lhs_str, rhs_str, lhs_type->type_name);

- ubsan_epilogue(&flags); + ubsan_epilogue(); out: user_access_restore(ua_flags); } @@ -411,11 +396,9 @@ EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);

void __ubsan_handle_builtin_unreachable(struct unreachable_data *data) { - unsigned long flags; - - ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location); pr_err("calling __builtin_unreachable()\n"); - ubsan_epilogue(&flags); + ubsan_epilogue(); panic("can't return from __builtin_unreachable()"); } EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable); @@ -423,19 +406,18 @@ EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable); void __ubsan_handle_load_invalid_value(struct invalid_value_data *data, void *val) { - unsigned long flags; char val_str[VALUE_LENGTH];

if (suppress_report(&data->location)) return;

- ubsan_prologue(&data->location, &flags); + ubsan_prologue(&data->location);

val_to_string(val_str, sizeof(val_str), data->type, val);

pr_err("load of value %s is not a valid value for type %s\n", val_str, data->type->type_name);

- ubsan_epilogue(&flags); + ubsan_epilogue(); } EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);