mirror of
https://github.com/brain-hackers/linux-brain.git
synced 2024-06-09 23:36:23 +09:00
80cd795630
44d8047f1d("binder: use standard functions to allocate fds") exposed a pre-existing issue in the binder driver. fdget() is used in ksys_ioctl() as a performance optimization. One of the rules associated with fdget() is that ksys_close() must not be called between the fdget() and the fdput(). There is a case where this requirement is not met in the binder driver which results in the reference count dropping to 0 when the device is still in use. This can result in use-after-free or other issues. If userpace has passed a file-descriptor for the binder driver using a BINDER_TYPE_FDA object, then kys_close() is called on it when handling a binder_ioctl(BC_FREE_BUFFER) command. This violates the assumptions for using fdget(). The problem is fixed by deferring the close using task_work_add(). A new variant of __close_fd() was created that returns a struct file with a reference. The fput() is deferred instead of using ksys_close(). Fixes:44d8047f1d("binder: use standard functions to allocate fds") Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Todd Kjos <tkjos@google.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
129 lines
3.3 KiB
C
129 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* descriptor table internals; you almost certainly want file.h instead.
|
|
*/
|
|
|
|
#ifndef __LINUX_FDTABLE_H
|
|
#define __LINUX_FDTABLE_H
|
|
|
|
#include <linux/posix_types.h>
|
|
#include <linux/compiler.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/nospec.h>
|
|
#include <linux/types.h>
|
|
#include <linux/init.h>
|
|
#include <linux/fs.h>
|
|
|
|
#include <linux/atomic.h>
|
|
|
|
/*
|
|
* The default fd array needs to be at least BITS_PER_LONG,
|
|
* as this is the granularity returned by copy_fdset().
|
|
*/
|
|
#define NR_OPEN_DEFAULT BITS_PER_LONG
|
|
|
|
struct fdtable {
|
|
unsigned int max_fds;
|
|
struct file __rcu **fd; /* current fd array */
|
|
unsigned long *close_on_exec;
|
|
unsigned long *open_fds;
|
|
unsigned long *full_fds_bits;
|
|
struct rcu_head rcu;
|
|
};
|
|
|
|
static inline bool close_on_exec(unsigned int fd, const struct fdtable *fdt)
|
|
{
|
|
return test_bit(fd, fdt->close_on_exec);
|
|
}
|
|
|
|
static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
|
|
{
|
|
return test_bit(fd, fdt->open_fds);
|
|
}
|
|
|
|
/*
|
|
* Open file table structure
|
|
*/
|
|
struct files_struct {
|
|
/*
|
|
* read mostly part
|
|
*/
|
|
atomic_t count;
|
|
bool resize_in_progress;
|
|
wait_queue_head_t resize_wait;
|
|
|
|
struct fdtable __rcu *fdt;
|
|
struct fdtable fdtab;
|
|
/*
|
|
* written part on a separate cache line in SMP
|
|
*/
|
|
spinlock_t file_lock ____cacheline_aligned_in_smp;
|
|
unsigned int next_fd;
|
|
unsigned long close_on_exec_init[1];
|
|
unsigned long open_fds_init[1];
|
|
unsigned long full_fds_bits_init[1];
|
|
struct file __rcu * fd_array[NR_OPEN_DEFAULT];
|
|
};
|
|
|
|
struct file_operations;
|
|
struct vfsmount;
|
|
struct dentry;
|
|
|
|
#define rcu_dereference_check_fdtable(files, fdtfd) \
|
|
rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))
|
|
|
|
#define files_fdtable(files) \
|
|
rcu_dereference_check_fdtable((files), (files)->fdt)
|
|
|
|
/*
|
|
* The caller must ensure that fd table isn't shared or hold rcu or file lock
|
|
*/
|
|
static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
|
|
{
|
|
struct fdtable *fdt = rcu_dereference_raw(files->fdt);
|
|
|
|
if (fd < fdt->max_fds) {
|
|
fd = array_index_nospec(fd, fdt->max_fds);
|
|
return rcu_dereference_raw(fdt->fd[fd]);
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
|
|
{
|
|
RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
|
|
!lockdep_is_held(&files->file_lock),
|
|
"suspicious rcu_dereference_check() usage");
|
|
return __fcheck_files(files, fd);
|
|
}
|
|
|
|
/*
|
|
* Check whether the specified fd has an open file.
|
|
*/
|
|
#define fcheck(fd) fcheck_files(current->files, fd)
|
|
|
|
struct task_struct;
|
|
|
|
struct files_struct *get_files_struct(struct task_struct *);
|
|
void put_files_struct(struct files_struct *fs);
|
|
void reset_files_struct(struct files_struct *);
|
|
int unshare_files(struct files_struct **);
|
|
struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy;
|
|
void do_close_on_exec(struct files_struct *);
|
|
int iterate_fd(struct files_struct *, unsigned,
|
|
int (*)(const void *, struct file *, unsigned),
|
|
const void *);
|
|
|
|
extern int __alloc_fd(struct files_struct *files,
|
|
unsigned start, unsigned end, unsigned flags);
|
|
extern void __fd_install(struct files_struct *files,
|
|
unsigned int fd, struct file *file);
|
|
extern int __close_fd(struct files_struct *files,
|
|
unsigned int fd);
|
|
extern int __close_fd_get_file(unsigned int fd, struct file **res);
|
|
|
|
extern struct kmem_cache *files_cachep;
|
|
|
|
#endif /* __LINUX_FDTABLE_H */
|