Re: [PATCH 1/2] topology: use bin_attribute to avoid buff overflow

From: Greg KH
Date: Wed Jun 02 2021 - 02:18:41 EST

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In reply to: tiantao (H): "Re: [PATCH 1/2] topology: use bin_attribute to avoid buff overflow"
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On Wed, Jun 02, 2021 at 02:14:49PM +0800, tiantao (H) wrote:
>
> 在 2021/6/1 12:58, Greg KH 写道:
> > On Tue, Jun 01, 2021 at 10:56:49AM +0800, Tian Tao wrote:
> > > Reading sys/devices/system/cpu/cpuX/topology/ returns cpu topology.
> > > However, the size of this file is limited to PAGE_SIZE because of the
> > > limitation for sysfs attribute. so we use bin_attribute instead of
> > > attribute to avoid NR_CPUS too big to cause buff overflow.
> > >
> > > This patch is based on the following discussion.
> > > https://www.spinics.net/lists/linux-doc/msg95921.html
> > Please use lore.kernel.org for links as we have no control over other
> > sites to ensure that they will work in the future. Use the message id
> > in the link as well, so that if something were to happen to lore, we can
> > figure it out.
> >
> > Also, you are modifying a bunch of different files here, do you mean to
> > do it for all of them?
> >
> > > Signed-off-by: Tian Tao <tiantao6@xxxxxxxxxxxxx>
> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> > > ---
> > > drivers/base/topology.c | 115 ++++++++++++++++++++++++++----------------------
> > > include/linux/bitmap.h | 3 ++
> > > include/linux/cpumask.h | 25 +++++++++++
> > > lib/bitmap.c | 34 ++++++++++++++
> > > 4 files changed, 125 insertions(+), 52 deletions(-)
> > >
> > > diff --git a/drivers/base/topology.c b/drivers/base/topology.c
> > > index 4d254fc..013edbb 100644
> > > --- a/drivers/base/topology.c
> > > +++ b/drivers/base/topology.c
> > > @@ -21,25 +21,27 @@ static ssize_t name##_show(struct device *dev, \
> > > return sysfs_emit(buf, "%d\n", topology_##name(dev->id)); \
> > > }
> > > -#define define_siblings_show_map(name, mask) \
> > > -static ssize_t name##_show(struct device *dev, \
> > > - struct device_attribute *attr, char *buf) \
> > > -{ \
> > > - return cpumap_print_to_pagebuf(false, buf, topology_##mask(dev->id));\
> > > +#define define_siblings_read_func(name, mask) \
> > > +static ssize_t name##_read(struct file *file, struct kobject *kobj, \
> > > + struct bin_attribute *attr, char *buf, \
> > > + loff_t off, size_t count) \
> > > +{ \
> > > + struct device *dev = kobj_to_dev(kobj); \
> > > + \
> > > + return cpumap_print_to_buf(false, buf, topology_##mask(dev->id), \
> > > + off, count); \
> > > +} \
> > > + \
> > > +static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \
> > > + struct bin_attribute *attr, char *buf, \
> > > + loff_t off, size_t count) \
> > > +{ \
> > > + struct device *dev = kobj_to_dev(kobj); \
> > > + \
> > > + return cpumap_print_to_buf(true, buf, topology_##mask(dev->id), \
> > > + off, count); \
> > > }
> > > -#define define_siblings_show_list(name, mask) \
> > > -static ssize_t name##_list_show(struct device *dev, \
> > > - struct device_attribute *attr, \
> > > - char *buf) \
> > > -{ \
> > > - return cpumap_print_to_pagebuf(true, buf, topology_##mask(dev->id));\
> > > -}
> > > -
> > > -#define define_siblings_show_func(name, mask) \
> > > - define_siblings_show_map(name, mask); \
> > > - define_siblings_show_list(name, mask)
> > > -
> > > define_id_show_func(physical_package_id);
> > > static DEVICE_ATTR_RO(physical_package_id);
> > > @@ -49,71 +51,80 @@ static DEVICE_ATTR_RO(die_id);
> > > define_id_show_func(core_id);
> > > static DEVICE_ATTR_RO(core_id);
> > > -define_siblings_show_func(thread_siblings, sibling_cpumask);
> > > -static DEVICE_ATTR_RO(thread_siblings);
> > > -static DEVICE_ATTR_RO(thread_siblings_list);
> > > +define_siblings_read_func(thread_siblings, sibling_cpumask);
> > > +static BIN_ATTR_RO(thread_siblings, 0);
> > > +static BIN_ATTR_RO(thread_siblings_list, 0);
> > > -define_siblings_show_func(core_cpus, sibling_cpumask);
> > > -static DEVICE_ATTR_RO(core_cpus);
> > > -static DEVICE_ATTR_RO(core_cpus_list);
> > > +define_siblings_read_func(core_cpus, sibling_cpumask);
> > > +static BIN_ATTR_RO(core_cpus, 0);
> > > +static BIN_ATTR_RO(core_cpus_list, 0);
> > > -define_siblings_show_func(core_siblings, core_cpumask);
> > > -static DEVICE_ATTR_RO(core_siblings);
> > > -static DEVICE_ATTR_RO(core_siblings_list);
> > > +define_siblings_read_func(core_siblings, core_cpumask);
> > > +static BIN_ATTR_RO(core_siblings, 0);
> > > +static BIN_ATTR_RO(core_siblings_list, 0);
> > > -define_siblings_show_func(die_cpus, die_cpumask);
> > > -static DEVICE_ATTR_RO(die_cpus);
> > > -static DEVICE_ATTR_RO(die_cpus_list);
> > > +define_siblings_read_func(die_cpus, die_cpumask);
> > > +static BIN_ATTR_RO(die_cpus, 0);
> > > +static BIN_ATTR_RO(die_cpus_list, 0);
> > > -define_siblings_show_func(package_cpus, core_cpumask);
> > > -static DEVICE_ATTR_RO(package_cpus);
> > > -static DEVICE_ATTR_RO(package_cpus_list);
> > > +define_siblings_read_func(package_cpus, core_cpumask);
> > > +static BIN_ATTR_RO(package_cpus, 0);
> > > +static BIN_ATTR_RO(package_cpus_list, 0);
> > > #ifdef CONFIG_SCHED_BOOK
> > > define_id_show_func(book_id);
> > > static DEVICE_ATTR_RO(book_id);
> > > -define_siblings_show_func(book_siblings, book_cpumask);
> > > -static DEVICE_ATTR_RO(book_siblings);
> > > -static DEVICE_ATTR_RO(book_siblings_list);
> > > +define_siblings_read_func(book_siblings, book_cpumask);
> > > +static BIN_ATTR_RO(book_siblings, 0);
> > > +static BIN_ATTR_RO(book_siblings_list, 0);
> > > #endif
> > > #ifdef CONFIG_SCHED_DRAWER
> > > define_id_show_func(drawer_id);
> > > static DEVICE_ATTR_RO(drawer_id);
> > > -define_siblings_show_func(drawer_siblings, drawer_cpumask);
> > > -static DEVICE_ATTR_RO(drawer_siblings);
> > > -static DEVICE_ATTR_RO(drawer_siblings_list);
> > > +define_siblings_read_func(drawer_siblings, drawer_cpumask);
> > > +static BIN_ATTR_RO(drawer_siblings, 0);
> > > +static BIN_ATTR_RO(drawer_siblings_list, 0);
> > > #endif
> > > +static struct bin_attribute *bin_attrs[] = {
> > > + &bin_attr_core_cpus,
> > > + &bin_attr_core_cpus_list,
> > > + &bin_attr_thread_siblings,
> > > + &bin_attr_thread_siblings_list,
> > > + &bin_attr_core_siblings,
> > > + &bin_attr_core_siblings_list,
> > > + &bin_attr_die_cpus,
> > > + &bin_attr_die_cpus_list,
> > > + &bin_attr_package_cpus,
> > > + &bin_attr_package_cpus_list,
> > > +#ifdef CONFIG_SCHED_BOOK
> > > + &bin_attr_book_siblings,
> > > + &bin_attr_book_siblings_list,
> > > +#endif
> > > +#ifdef CONFIG_SCHED_DRAWER
> > > + &bin_attr_drawer_siblings,
> > > + &bin_attr_drawer_siblings_list,
> > > +#endif
> > > + NULL,
> > > +};
> > > +
> > > static struct attribute *default_attrs[] = {
> > > &dev_attr_physical_package_id.attr,
> > > &dev_attr_die_id.attr,
> > > &dev_attr_core_id.attr,
> > > - &dev_attr_thread_siblings.attr,
> > > - &dev_attr_thread_siblings_list.attr,
> > > - &dev_attr_core_cpus.attr,
> > > - &dev_attr_core_cpus_list.attr,
> > > - &dev_attr_core_siblings.attr,
> > > - &dev_attr_core_siblings_list.attr,
> > > - &dev_attr_die_cpus.attr,
> > > - &dev_attr_die_cpus_list.attr,
> > > - &dev_attr_package_cpus.attr,
> > > - &dev_attr_package_cpus_list.attr,
> > > #ifdef CONFIG_SCHED_BOOK
> > > &dev_attr_book_id.attr,
> > > - &dev_attr_book_siblings.attr,
> > > - &dev_attr_book_siblings_list.attr,
> > > #endif
> > > #ifdef CONFIG_SCHED_DRAWER
> > > &dev_attr_drawer_id.attr,
> > > - &dev_attr_drawer_siblings.attr,
> > > - &dev_attr_drawer_siblings_list.attr,
> > > #endif
> > > NULL
> > > };
> > > static const struct attribute_group topology_attr_group = {
> > > .attrs = default_attrs,
> > > + .bin_attrs = bin_attrs,
> > > .name = "topology"
> > > };
> > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> > > index 70a9324..bc401bd9b 100644
> > > --- a/include/linux/bitmap.h
> > > +++ b/include/linux/bitmap.h
> > > @@ -219,6 +219,9 @@ extern unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int
> > > extern int bitmap_print_to_pagebuf(bool list, char *buf,
> > > const unsigned long *maskp, int nmaskbits);
> > > +extern int bitmap_print_to_buf(bool list, char *buf,
> > > + const unsigned long *maskp, int nmaskbits, loff_t off, size_t count);
> > > +
> > > #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
> > > #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
> > > diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> > > index 383684e..e4810b3e 100644
> > > --- a/include/linux/cpumask.h
> > > +++ b/include/linux/cpumask.h
> > > @@ -928,6 +928,31 @@ cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask)
> > > nr_cpu_ids);
> > > }
> > > +/**
> > > + * cpumap_print_to_buf - copies the cpumask into the buffer either
> > > + * as comma-separated list of cpus or hex values of cpumask
> > > + * @list: indicates whether the cpumap must be list
> > > + * @mask: the cpumask to copy
> > > + * @buf: the buffer to copy into
> > > + * @off: the offset that buffer to copy into
> > > + * @count: the count thatbuffer to copy into
> > > + *
> > > + * the role of cpumap_print_to_buf and cpumap_print_to_pagebuf is
> > > + * the same, the difference is that the second parameter of
> > > + * bitmap_print_to_buf can be more than one pagesize.
> > > + *
> > > + * Returns the length of the (null-terminated) @buf string, zero if
> > > + * nothing is copied.
> > > + */
> > > +
> > > +static inline ssize_t
> > > +cpumap_print_to_buf(bool list, char *buf, const struct cpumask *mask,
> > > + loff_t off, size_t count)
> > > +{
> > > + return bitmap_print_to_buf(list, buf, cpumask_bits(mask),
> > > + nr_cpu_ids, off, count);
> > > +}
> > > +
> > > #if NR_CPUS <= BITS_PER_LONG
> > > #define CPU_MASK_ALL \
> > > (cpumask_t) { { \
> > > diff --git a/lib/bitmap.c b/lib/bitmap.c
> > > index 75006c4..5bf89f1 100644
> > > --- a/lib/bitmap.c
> > > +++ b/lib/bitmap.c
> > > @@ -460,6 +460,40 @@ int bitmap_parse_user(const char __user *ubuf,
> > > EXPORT_SYMBOL(bitmap_parse_user);
> > > /**
> > > + * bitmap_print_to_buf - convert bitmap to list or hex format ASCII string
> > > + * @list: indicates whether the bitmap must be list
> > > + * @buf: page aligned buffer into which string is placed
> > > + * @maskp: pointer to bitmap to convert
> > > + * @nmaskbits: size of bitmap, in bits
> > > + * @off: offset in buf
> > > + * @count: count that already output
> > > + *
> > > + * the role of bitmap_print_to_buf and bitmap_print_to_pagebuf is
> > > + * the same, the difference is that the second parameter of
> > > + * bitmap_print_to_buf can be more than one pagesize.
> > > + */
> > > +int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> > > + int nmaskbits, loff_t off, size_t count)
> > > +{
> > > + int len, size;
> > > + void *data;
> > > + char *fmt = list ? "%*pbl\n" : "%*pb\n";
> > > +
> > > + len = snprintf(NULL, 0, fmt, nmaskbits, maskp);
> > > +
> > > + data = kvmalloc(len+1, GFP_KERNEL);
> > > + if (!data)
> > > + return -ENOMEM;
> > > +
> > > + size = scnprintf(data, len+1, fmt, nmaskbits, maskp);
> > > + size = memory_read_from_buffer(buf, count, &off, data, size);
> > > + kvfree(data);
> > > +
> > > + return size;
> > Why is this so different from bitmap_print_to_pagebuf()? Can't you just
> > use this function as the "real" function and then change
> > bitmap_print_to_pagebuf() to call it with a size of PAGE_SIZE?
>
> Do you mean do following change, is that correct? :-)

Maybe, it is whitespace corrupted, and it still feels like this function
is much bigger than it needs to be given the function it is replacing is
only a simple sprintf() call.

> +int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> +                       int nmaskbits, loff_t off, size_t count)
> +{
> +       int len, size;
> +       void *data;
> +       const char *fmt = list ? "%*pbl\n" : "%*pb\n";
> +
> +       if (off == LLONG_MAX && count == PAGE_SIZE - offset_in_page(buf))
> +               return scnprintf(buf, count, fmt, nmaskbits, maskp);
> +
> +       len = snprintf(NULL, 0, fmt, nmaskbits, maskp);
> +
> +       data = kvmalloc(len+1, GFP_KERNEL);

Why do you need to allocate more memory? And why kvmalloc()?

> +       if (!data)
> +               return -ENOMEM;
> +
> +       size = scnprintf(data, len+1, fmt, nmaskbits, maskp);
> +
> +       size = memory_read_from_buffer(buf, count, &off, data, size);
> +       kvfree(data);
> +
> +       return size;
> +}
> +EXPORT_SYMBOL(bitmap_print_to_buf);

thanks,

greg k-h

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In reply to: tiantao (H): "Re: [PATCH 1/2] topology: use bin_attribute to avoid buff overflow"
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