nilfs2: fix CFI failure when accessing /sys/fs/nilfs2/features/*

Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

kernel os linux

When accessing one of the files under /sys/fs/nilfs2/features when
CONFIG_CFI_CLANG is enabled, there is a CFI violation:

CFI failure at kobj_attr_show+0x59/0x80 (target: nilfs_feature_revision_show+0x0/0x30; expected type: 0xfc392c4d)
...
Call Trace:
<TASK>
sysfs_kf_seq_show+0x2a6/0x390
? __cfi_kobj_attr_show+0x10/0x10
kernfs_seq_show+0x104/0x15b
seq_read_iter+0x580/0xe2b
...

When the kobject of the kset for /sys/fs/nilfs2 is initialized, its ktype
is set to kset_ktype, which has a ->sysfs_ops of kobj_sysfs_ops. When
nilfs_feature_attr_group is added to that kobject via
sysfs_create_group(), the kernfs_ops of each files is sysfs_file_kfops_rw,
which will call sysfs_kf_seq_show() when ->seq_show() is called.
sysfs_kf_seq_show() in turn calls kobj_attr_show() through
->sysfs_ops->show(). kobj_attr_show() casts the provided attribute out to
a 'struct kobj_attribute' via container_of() and calls ->show(), resulting
in the CFI violation since neither nilfs_feature_revision_show() nor
nilfs_feature_README_show() match the prototype of ->show() in 'struct
kobj_attribute'.

Resolve the CFI violation by adjusting the second parameter in
nilfs_feature_{revision,README}_show() from 'struct attribute' to 'struct
kobj_attribute' to match the expected prototype.

Link: https://lkml.kernel.org/r/20250906144410.22511-1-konishi.ryusuke@gmail.com
Fixes: aebe17f68444 ("nilfs2: add /sys/fs/nilfs2/features group")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202509021646.bc78d9ef-lkp@intel.com/
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

authored by

Nathan Chancellor and committed by

Andrew Morton 9 months ago 025e87f8 c62cff40

+6 -6

2 changed files

expand all

nilfs2

sysfs.c

sysfs.h

+2 -2

fs/nilfs2/sysfs.c

··· 1075 1075 ************************************************************************/ 1076 1076 1077 1077 static ssize_t nilfs_feature_revision_show(struct kobject *kobj, 1078 - struct attribute *attr, char *buf) 1078 + struct kobj_attribute *attr, char *buf) 1079 1079 { 1080 1080 return sysfs_emit(buf, "%d.%d\n", 1081 1081 NILFS_CURRENT_REV, NILFS_MINOR_REV); ··· 1087 1087 "(1) revision\n\tshow current revision of NILFS file system driver.\n"; 1088 1088 1089 1089 static ssize_t nilfs_feature_README_show(struct kobject *kobj, 1090 - struct attribute *attr, 1090 + struct kobj_attribute *attr, 1091 1091 char *buf) 1092 1092 { 1093 1093 return sysfs_emit(buf, features_readme_str);

+4 -4

fs/nilfs2/sysfs.h

··· 50 50 struct completion sg_segments_kobj_unregister; 51 51 }; 52 52 53 - #define NILFS_COMMON_ATTR_STRUCT(name) \ 53 + #define NILFS_KOBJ_ATTR_STRUCT(name) \ 54 54 struct nilfs_##name##_attr { \ 55 55 struct attribute attr; \ 56 - ssize_t (*show)(struct kobject *, struct attribute *, \ 56 + ssize_t (*show)(struct kobject *, struct kobj_attribute *, \ 57 57 char *); \ 58 - ssize_t (*store)(struct kobject *, struct attribute *, \ 58 + ssize_t (*store)(struct kobject *, struct kobj_attribute *, \ 59 59 const char *, size_t); \ 60 60 } 61 61 62 - NILFS_COMMON_ATTR_STRUCT(feature); 62 + NILFS_KOBJ_ATTR_STRUCT(feature); 63 63 64 64 #define NILFS_DEV_ATTR_STRUCT(name) \ 65 65 struct nilfs_##name##_attr { \

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