From: Julien Grall Date: Fri, 20 Sep 2019 11:08:35 +0100 Subject: [PATCH 304/342] lib/ubsan: Don't seralize UBSAN report Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=9d8814df58e1f97746fa2da50d282d631c11542d [ Upstream commit 4702c28ac777b27acb499cbd5e8e787ce1a7d82d ] 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 | Preemption disabled at: | [] 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 to be interleaved. However, they can still interleave with other messages (and even splat from __migth_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: https://lkml.kernel.org/r/20190920100835.14999-1-julien.grall@arm.com Reported-by: Andre Przywara Signed-off-by: Julien Grall Acked-by: Andrey Ryabinin Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- lib/ubsan.c | 64 +++++++++++++++++++---------------------------------- 1 file changed, 23 insertions(+), 41 deletions(-) diff --git a/lib/ubsan.c b/lib/ubsan.c index 1e9e2ab25539..5830cc9a2164 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -143,25 +143,21 @@ 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--; } @@ -170,14 +166,13 @@ 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); @@ -189,7 +184,7 @@ 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, @@ -217,20 +212,19 @@ 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); @@ -238,13 +232,12 @@ 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); @@ -254,58 +247,52 @@ 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, @@ -369,25 +356,23 @@ EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive); 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]; @@ -396,7 +381,7 @@ void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data, if (suppress_report(&data->location)) return; - 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); @@ -419,18 +404,16 @@ 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(); } 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); @@ -438,19 +421,18 @@ 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);