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fs/file_table: split fget_light

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due to systemd updated, sun8i kernel doesn't compact to new systemd.
after check systemd code, it return -EBADF in below code:

https://github.com/systemd/systemd/blob/master/src/basic/fs-util.c#L804-L815

fstat on path fds (open with O_PATH).

after check sun8i kernel code, in fstat path, fget_light rectly returns
NULL on path fds (file->f_mode & FMODE_PATH).

on mainline kernel, fget_light is wraper function of __fget_light.
on fstat path, it uses __fget_light, doesn't check FMODE_PATH.

so follow mainline kernel, change the behavior of sun8i kernel.

test case:

int main(int argc, char **argv)
{
    int fd;
    struct stat previous_stat;

    fd =  open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH);
    if (fd < 0) {
        printf("%d, %s\n", __LINE__,  strerror(errno));
         return -errno;
    }

    if(fstat(fd, &previous_stat) < 0) {

        printf("%d, %s\n", __LINE__, strerror(errno));
        return -errno;
    }
}

expect no error.

Signed-off-by: Zhang Ning <832666+zhangn1985@users.noreply.github.com>
This commit is contained in:
Zhang Ning
2019-01-27 18:37:00 +08:00
parent 002a60c148
commit ca925a740a
3 changed files with 10 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
fs/file_table.c
View File

@@ -322,7 +322,7 @@ EXPORT_SYMBOL(fget_raw);
* The fput_needed flag returned by fget_light should be passed to the
* corresponding fput_light.
*/
struct file *fget_light(unsigned int fd, int *fput_needed)
struct file *__fget_light(unsigned int fd, fmode_t mode, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
@@ -330,13 +330,13 @@ struct file *fget_light(unsigned int fd, int *fput_needed)
*fput_needed = 0;
if (atomic_read(&files->count) == 1) {
file = fcheck_files(files, fd);
if (file && (file->f_mode & FMODE_PATH))
if (file && (file->f_mode & mode))
file = NULL;
} else {
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (!(file->f_mode & FMODE_PATH) &&
if (!(file->f_mode & mode) &&
atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
@@ -349,6 +349,11 @@ struct file *fget_light(unsigned int fd, int *fput_needed)
return file;
}
struct file *fget_light(unsigned int fd, int *fput_needed)
{
return __fget_light(fd, FMODE_PATH, fput_needed);
}
struct file *fget_raw_light(unsigned int fd, int *fput_needed)
{
struct file *file;

2
fs/stat.c
View File

@@ -58,7 +58,7 @@ EXPORT_SYMBOL(vfs_getattr);
int vfs_fstat(unsigned int fd, struct kstat *stat)
{
int fput_needed;
struct file *f = fget_light(fd, &fput_needed);
struct file *f = __fget_light(fd, 0, &fput_needed);
int error = -EBADF;
if (f) {

1
include/linux/file.h
View File

@@ -28,6 +28,7 @@ static inline void fput_light(struct file *file, int fput_needed)
extern struct file *fget(unsigned int fd);
extern struct file *fget_light(unsigned int fd, int *fput_needed);
extern struct file *__fget_light(unsigned int fd, fmode_t mode, int *fput_needed);
extern struct file *fget_raw(unsigned int fd);
extern struct file *fget_raw_light(unsigned int fd, int *fput_needed);
extern void set_close_on_exec(unsigned int fd, int flag);