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    Subject[PATCH RT 13/25] lib/ubsan: Don't seralize UBSAN report
    Date
    From: Julien Grall <julien.grall@arm.com>

    v4.14.170-rt75-rc1 stable review patch.
    If anyone has any objections, please let me know.

    -----------


    [ Upstream commmit 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:
    | [<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 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 <andre.przywara@arm.com>
    Signed-off-by: Julien Grall <julien.grall@arm.com>
    Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Tom Zanussi <zanussi@kernel.org>

    Conflicts:
    lib/ubsan.c
    ---
    lib/ubsan.c | 76 ++++++++++++++++++++++---------------------------------------
    1 file changed, 27 insertions(+), 49 deletions(-)

    diff --git a/lib/ubsan.c b/lib/ubsan.c
    index c652b4a820cc..f94cfb3a41ed 100644
    --- a/lib/ubsan.c
    +++ b/lib/ubsan.c
    @@ -147,26 +147,21 @@ static bool location_is_valid(struct source_location *loc)
    {
    return loc->file_name != NULL;
    }
    -
    -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--;
    }

    @@ -175,14 +170,13 @@ 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);
    @@ -194,7 +188,7 @@ 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,
    @@ -222,20 +216,19 @@ 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);

    @@ -243,13 +236,12 @@ 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);

    @@ -259,58 +251,52 @@ 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,
    @@ -356,12 +342,10 @@ EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);

    void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
    {
    - unsigned long flags;
    -
    if (suppress_report(&data->location))
    return;

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

    pr_err("null pointer returned from function declared to never return null\n");

    @@ -369,49 +353,46 @@ void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
    print_source_location("returns_nonnull attribute specified in",
    &data->attr_location);

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

    void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
    void *bound)
    {
    - unsigned long flags;
    char bound_str[VALUE_LENGTH];

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

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

    val_to_string(bound_str, sizeof(bound_str), data->type, bound);
    pr_err("variable length array bound value %s <= 0\n", bound_str);

    - ubsan_epilogue(&flags);
    + ubsan_epilogue();
    }
    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];
    @@ -420,7 +401,7 @@ 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);
    @@ -443,18 +424,16 @@ 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);
    @@ -462,19 +441,18 @@ 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);
    --
    2.14.1
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      Last update: 2020-02-21 22:27    [W:6.481 / U:1.192 seconds]
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