From: Al Viro <viro@zeniv.linux.org.uk>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Alexey Gladkov <gladkov.alexey@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
syzbot <syzbot+c1af344512918c61362c@syzkaller.appspotmail.com>,
jmorris@namei.org, linux-kernel@vger.kernel.org,
linux-next@vger.kernel.org,
linux-security-module@vger.kernel.org, serge@hallyn.com,
sfr@canb.auug.org.au, syzkaller-bugs@googlegroups.com,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: linux-next boot error: general protection fault in tomoyo_get_local_path
Date: Fri, 15 May 2020 21:13:57 +0100 [thread overview]
Message-ID: <20200515201357.GG23230@ZenIV.linux.org.uk> (raw)
In-Reply-To: <72cb7aea-92bd-d71b-2f8a-63881a35fad8@i-love.sakura.ne.jp>
On Sat, May 16, 2020 at 12:36:28AM +0900, Tetsuo Handa wrote:
> On 2020/05/16 0:18, Tetsuo Handa wrote:
> > This is
> >
> > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
> > char *ep;
> > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
> > struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry)); // <= here
> >
> > if (*ep == '/' && pid && pid ==
> > task_tgid_nr_ns(current, proc_pidns)) {
> >
> > which was added by commit c59f415a7cb6e1e1 ("Use proc_pid_ns() to get pid_namespace from the proc superblock").
> >
> > @@ -161,9 +162,10 @@ static char *tomoyo_get_local_path(struct dentry *dentry, char * const buffer,
> > if (sb->s_magic == PROC_SUPER_MAGIC && *pos == '/') {
> > char *ep;
> > const pid_t pid = (pid_t) simple_strtoul(pos + 1, &ep, 10);
> > + struct pid_namespace *proc_pidns = proc_pid_ns(d_inode(dentry));
> >
> > if (*ep == '/' && pid && pid ==
> > - task_tgid_nr_ns(current, sb->s_fs_info)) {
> > + task_tgid_nr_ns(current, proc_pidns)) {
> > pos = ep - 5;
> > if (pos < buffer)
> > goto out;
> >
> > Alexey and Eric, any clue?
> >
>
> A similar bug (racing inode destruction with open() on proc filesystem) was fixed as
> commit 6f7c41374b62fd80 ("tomoyo: Don't use nifty names on sockets."). Then, it might
> not be safe to replace dentry->d_sb->s_fs_info with dentry->d_inode->i_sb->s_fs_info .
Could you explain why do you want to bother with d_inode() anyway? Anything that
does dentry->d_inode->i_sb can bloody well use dentry->d_sb. And that's never
changed over the struct dentry lifetime - ->d_sb is set on allocation and never
modified afterwards.
next prev parent reply other threads:[~2020-05-15 20:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-15 14:46 linux-next boot error: general protection fault in tomoyo_get_local_path syzbot
2020-05-15 15:18 ` Tetsuo Handa
2020-05-15 15:36 ` Tetsuo Handa
2020-05-15 20:13 ` Al Viro [this message]
2020-05-15 20:36 ` Eric W. Biederman
2020-05-15 20:56 ` Al Viro
2020-05-15 18:16 ` Eric W. Biederman
2020-05-15 19:25 ` Alexey Gladkov
2020-05-17 17:11 ` [PATCH] proc: proc_pid_ns takes super_block as an argument Alexey Gladkov
2020-05-18 11:17 ` [PATCH v2] " Alexey Gladkov
2020-05-18 12:08 ` Eric W. Biederman
2020-05-18 12:56 ` Alexey Gladkov
2020-05-18 12:57 ` Eric W. Biederman
2020-05-18 15:08 ` [PATCH v3] " Alexey Gladkov
2020-05-18 15:36 ` Tetsuo Handa
2020-05-18 18:07 ` [PATCH v4] " Alexey Gladkov
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