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tmpfs: Fix type for sysfs' casefold attribute

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DEVICE_STRING_ATTR_RO should be only used by device drivers since it
relies on `struct device` to use device_show_string() function. Using
this with non device code led to a kCFI violation:

> cat /sys/fs/tmpfs/features/casefold
[   70.558496] CFI failure at kobj_attr_show+0x2c/0x4c (target: device_show_string+0x0/0x38; expected type: 0xc527b809)

Like the other filesystems, fix this by manually declaring the attribute
using kobj_attribute() and writing a proper show() function.

Also, leave macros for anyone that need to expand tmpfs sysfs' with
more attributes.

Fixes: 5132f08bd3 ("tmpfs: Expose filesystem features via sysfs")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://lore.kernel.org/lkml/20241031051822.GA2947788@thelio-3990X/
Signed-off-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20241101164251.327884-3-andrealmeid@igalia.com
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
André Almeida 2024-11-01 13:42:50 -03:00 committed by Christian Brauner
parent 33b091c08e
commit 18d2f10f62
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 27 additions and 2 deletions
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29
mm/shmem.c
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@ -5548,13 +5548,38 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
EXPORT_SYMBOL_GPL(shmem_read_mapping_page_gfp);
#if defined(CONFIG_SYSFS) && defined(CONFIG_TMPFS)
#define __INIT_KOBJ_ATTR(_name, _mode, _show, _store) \
{ \
.attr = { .name = __stringify(_name), .mode = _mode }, \
.show = _show, \
.store = _store, \
}
#define TMPFS_ATTR_W(_name, _store) \
static struct kobj_attribute tmpfs_attr_##_name = \
__INIT_KOBJ_ATTR(_name, 0200, NULL, _store)
#define TMPFS_ATTR_RW(_name, _show, _store) \
static struct kobj_attribute tmpfs_attr_##_name = \
__INIT_KOBJ_ATTR(_name, 0644, _show, _store)
#define TMPFS_ATTR_RO(_name, _show) \
static struct kobj_attribute tmpfs_attr_##_name = \
__INIT_KOBJ_ATTR(_name, 0444, _show, NULL)
#if IS_ENABLED(CONFIG_UNICODE)
static DEVICE_STRING_ATTR_RO(casefold, 0444, "supported");
static ssize_t casefold_show(struct kobject *kobj, struct kobj_attribute *a,
char *buf)
{
return sysfs_emit(buf, "supported\n");
}
TMPFS_ATTR_RO(casefold, casefold_show);
#endif
static struct attribute *tmpfs_attributes[] = {
#if IS_ENABLED(CONFIG_UNICODE)
&dev_attr_casefold.attr.attr,
&tmpfs_attr_casefold.attr,
#endif
NULL
};