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proc: s_fs_info may be NULL when proc_kill_sb is called 

syzbot found that proc_fill_super() fails before filling up sb->s_fs_info,
deactivate_locked_super() will be called and sb->s_fs_info will be NULL.
The proc_kill_sb() does not expect fs_info to be NULL which is wrong.

Link: https://lore.kernel.org/lkml/0000000000002d7ca605a7b8b1c5@google.com
Reported-by: syzbot+4abac52934a48af5ff19@syzkaller.appspotmail.com
Fixes: fa10fed30f ("proc: allow to mount many instances of proc in one pid namespace")
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov 2020-06-10 20:35:49 +02:00 committed by Eric W. Biederman
parent 9d78edeaec
commit 058f2e4da7
1 changed files with 6 additions and 4 deletions
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10
fs/proc/root.c
View File

@ -264,11 +264,13 @@ static void proc_kill_sb(struct super_block *sb)
{
struct proc_fs_info *fs_info = proc_sb_info(sb);
if (fs_info->proc_self)
dput(fs_info->proc_self);
if (!fs_info) {
kill_anon_super(sb);
return;
}
if (fs_info->proc_thread_self)
dput(fs_info->proc_thread_self);
dput(fs_info->proc_self);
dput(fs_info->proc_thread_self);
kill_anon_super(sb);
put_pid_ns(fs_info->pid_ns);