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@xxxxxxxxxx Reported-by: syzbot+4abac52934a48af5ff19@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: fa10fed30f25 ("proc: allow to mount many instances of proc in one pid namespace") Signed-off-by: Alexey Gladkov <gladkov.alexey@xxxxxxxxx> --- fs/proc/root.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/fs/proc/root.c b/fs/proc/root.c index ffebed1999e5..a715eb9f196a 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -264,15 +264,18 @@ 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) { + if (fs_info->proc_self) + dput(fs_info->proc_self); - if (fs_info->proc_thread_self) - dput(fs_info->proc_thread_self); + if (fs_info->proc_thread_self) + dput(fs_info->proc_thread_self); + + put_pid_ns(fs_info->pid_ns); + kfree(fs_info); + } kill_anon_super(sb); - put_pid_ns(fs_info->pid_ns); - kfree(fs_info); } static struct file_system_type proc_fs_type = { -- 2.25.4
