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devpts: if initialization failed, don't crash when opening /dev/ptmx 

If devpts failed to initialize, it would store an ERR_PTR in the global
devpts_mnt.  A subsequent open of /dev/ptmx would call devpts_new_index,
which would dereference devpts_mnt and crash.

Avoid storing invalid values in devpts_mnt; leave it NULL instead.  Make
both devpts_new_index and devpts_pty_new fail gracefully with ENODEV in
that case, which then becomes the return value to the userspace open call
on /dev/ptmx.

[akpm@linux-foundation.org: remove unneeded static]
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Josh Triplett 2015-06-30 14:58:27 -07:00 committed by Linus Torvalds
parent 15f1d82781
commit 9ce71148b0
1 changed files with 24 additions and 7 deletions
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31
fs/devpts/inode.c
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@ -142,6 +142,8 @@ static inline struct super_block *pts_sb_from_inode(struct inode *inode)
if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
return inode->i_sb;
#endif
if (!devpts_mnt)
return NULL;
return devpts_mnt->mnt_sb;
}
@ -525,10 +527,14 @@ static struct file_system_type devpts_fs_type = {
int devpts_new_index(struct inode *ptmx_inode)
{
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_fs_info *fsi;
int index;
int ida_ret;
if (!sb)
return -ENODEV;
fsi = DEVPTS_SB(sb);
retry:
if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
return -ENOMEM;
@ -584,11 +590,18 @@ struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index,
struct dentry *dentry;
struct super_block *sb = pts_sb_from_inode(ptmx_inode);
struct inode *inode;
struct dentry *root = sb->s_root;
struct pts_fs_info *fsi = DEVPTS_SB(sb);
struct pts_mount_opts *opts = &fsi->mount_opts;
struct dentry *root;
struct pts_fs_info *fsi;
struct pts_mount_opts *opts;
char s[12];
if (!sb)
return ERR_PTR(-ENODEV);
root = sb->s_root;
fsi = DEVPTS_SB(sb);
opts = &fsi->mount_opts;
inode = new_inode(sb);
if (!inode)
return ERR_PTR(-ENOMEM);
@ -676,12 +689,16 @@ static int __init init_devpts_fs(void)
struct ctl_table_header *table;
if (!err) {
struct vfsmount *mnt;
table = register_sysctl_table(pty_root_table);
devpts_mnt = kern_mount(&devpts_fs_type);
if (IS_ERR(devpts_mnt)) {
err = PTR_ERR(devpts_mnt);
mnt = kern_mount(&devpts_fs_type);
if (IS_ERR(mnt)) {
err = PTR_ERR(mnt);
unregister_filesystem(&devpts_fs_type);
unregister_sysctl_table(table);
} else {
devpts_mnt = mnt;
}
}
return err;