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ANDROID: Add filp_open_block() for zram

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We currently plan to disallow use of filp_open() from drivers in GKI,
however the ZRAM driver still needs it. Add a new GKI-only variant of
filp_open() which only permits a block device to be opened, which can
be exported instead. This keeps ZRAM working but cuts down on drivers
that attempt to open and write files in kernel mode.

Bug: 179220339
Change-Id: Id696b4aaf204b0499ce0a1b6416648670236e570
Signed-off-by: Alistair Delva <adelva@google.com>
This commit is contained in:
Alistair Delva
2021-02-02 17:10:49 -08:00
parent 71037045e8
commit cf8f7947f2
3 changed files with 22 additions and 1 deletions
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2
drivers/block/zram/zram_drv.c
View File

@@ -477,7 +477,7 @@ static ssize_t backing_dev_store(struct device *dev,
if (sz > 0 && file_name[sz - 1] == '\n')
file_name[sz - 1] = 0x00;
backing_dev = filp_open(file_name, O_RDWR|O_LARGEFILE, 0);
backing_dev = filp_open_block(file_name, O_RDWR|O_LARGEFILE, 0);
if (IS_ERR(backing_dev)) {
err = PTR_ERR(backing_dev);
backing_dev = NULL;

20
fs/open.c
View File

@@ -1141,6 +1141,26 @@ struct file *filp_open(const char *filename, int flags, umode_t mode)
}
EXPORT_SYMBOL(filp_open);
/* ANDROID: Allow drivers to open only block files from kernel mode */
struct file *filp_open_block(const char *filename, int flags, umode_t mode)
{
struct file *file;
file = filp_open(filename, flags, mode);
if (IS_ERR(file))
goto err_out;
/* Drivers should only be allowed to open block devices */
if (!S_ISBLK(file->f_mapping->host->i_mode)) {
filp_close(file, NULL);
file = ERR_PTR(-ENOTBLK);
}
err_out:
return file;
}
EXPORT_SYMBOL_GPL(filp_open_block);
struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
const char *filename, int flags, umode_t mode)
{

1
include/linux/fs.h
View File

@@ -2528,6 +2528,7 @@ extern long do_sys_open(int dfd, const char __user *filename, int flags,
umode_t mode);
extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *filp_open_block(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
const char *, int, umode_t);
extern struct file * dentry_open(const struct path *, int, const struct cred *);