sysfs: fix use after free in case of concurrent read/write and readdir
The inode->i_mutex isn't hold when updating filp->f_pos in read()/write(), so the filp->f_pos might be read as 0 or 1 in readdir() when there is concurrent read()/write() on this same file, then may cause use after free in readdir(). The bug can be reproduced with Li Zefan's test code on the link: https://patchwork.kernel.org/patch/2160771/ This patch fixes the use after free under this situation. Cc: stable <stable@vger.kernel.org> Reported-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
0f8b1a0204
commit
f7db5e7660
fs/sysfs
|
@ -999,6 +999,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
|
||||||
enum kobj_ns_type type;
|
enum kobj_ns_type type;
|
||||||
const void *ns;
|
const void *ns;
|
||||||
ino_t ino;
|
ino_t ino;
|
||||||
|
loff_t off;
|
||||||
|
|
||||||
type = sysfs_ns_type(parent_sd);
|
type = sysfs_ns_type(parent_sd);
|
||||||
ns = sysfs_info(dentry->d_sb)->ns[type];
|
ns = sysfs_info(dentry->d_sb)->ns[type];
|
||||||
|
@ -1021,6 +1022,7 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
|
||||||
return 0;
|
return 0;
|
||||||
}
|
}
|
||||||
mutex_lock(&sysfs_mutex);
|
mutex_lock(&sysfs_mutex);
|
||||||
|
off = filp->f_pos;
|
||||||
for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
|
for (pos = sysfs_dir_pos(ns, parent_sd, filp->f_pos, pos);
|
||||||
pos;
|
pos;
|
||||||
pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {
|
pos = sysfs_dir_next_pos(ns, parent_sd, filp->f_pos, pos)) {
|
||||||
|
@ -1032,19 +1034,24 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
|
||||||
len = strlen(name);
|
len = strlen(name);
|
||||||
ino = pos->s_ino;
|
ino = pos->s_ino;
|
||||||
type = dt_type(pos);
|
type = dt_type(pos);
|
||||||
filp->f_pos = pos->s_hash;
|
off = filp->f_pos = pos->s_hash;
|
||||||
filp->private_data = sysfs_get(pos);
|
filp->private_data = sysfs_get(pos);
|
||||||
|
|
||||||
mutex_unlock(&sysfs_mutex);
|
mutex_unlock(&sysfs_mutex);
|
||||||
ret = filldir(dirent, name, len, filp->f_pos, ino, type);
|
ret = filldir(dirent, name, len, off, ino, type);
|
||||||
mutex_lock(&sysfs_mutex);
|
mutex_lock(&sysfs_mutex);
|
||||||
if (ret < 0)
|
if (ret < 0)
|
||||||
break;
|
break;
|
||||||
}
|
}
|
||||||
mutex_unlock(&sysfs_mutex);
|
mutex_unlock(&sysfs_mutex);
|
||||||
if ((filp->f_pos > 1) && !pos) { /* EOF */
|
|
||||||
filp->f_pos = INT_MAX;
|
/* don't reference last entry if its refcount is dropped */
|
||||||
|
if (!pos) {
|
||||||
filp->private_data = NULL;
|
filp->private_data = NULL;
|
||||||
|
|
||||||
|
/* EOF and not changed as 0 or 1 in read/write path */
|
||||||
|
if (off == filp->f_pos && off > 1)
|
||||||
|
filp->f_pos = INT_MAX;
|
||||||
}
|
}
|
||||||
return 0;
|
return 0;
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in New Issue