Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Eric Biggers <ebiggers@kernel.org>
To: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Cc: linux-kernel-mentees@lists.linuxfoundation.org,
	syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fs: fix KMSAN uninit-value bug by initializing nd in do_file_open_root
Date: Tue, 15 Sep 2020 22:41:57 -0700	[thread overview]
Message-ID: <20200916054157.GC825@sol.localdomain> (raw)
In-Reply-To: <20200916052657.18683-1-anant.thazhemadam@gmail.com>

On Wed, Sep 16, 2020 at 10:56:56AM +0530, Anant Thazhemadam wrote:
> The KMSAN bug report for the bug indicates that there exists;
> Local variable ----nd@do_file_open_root created at:
>  do_file_open_root+0xa4/0xb40 fs/namei.c:3385
>  do_file_open_root+0xa4/0xb40 fs/namei.c:3385
> 
> Initializing nd fixes this issue, and doesn't break anything else either
> 
> Fixes: https://syzkaller.appspot.com/bug?extid=4191a44ad556eacc1a7a
> Reported-by: syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com
> Tested-by: syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> ---
>  fs/namei.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index e99e2a9da0f7..b27382586209 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3404,7 +3404,7 @@ struct file *do_filp_open(int dfd, struct filename *pathname,
>  struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
>  		const char *name, const struct open_flags *op)
>  {
> -	struct nameidata nd;
> +	struct nameidata nd = {};
>  	struct file *file;
>  	struct filename *filename;
>  	int flags = op->lookup_flags | LOOKUP_ROOT;

Looking at the actual KMSAN report, it looks like it's nameidata::dir_mode or
nameidata::dir_uid that is uninitialized.  You need to figure out the correct
solution, not just blindly initialize with zeroes -- that could hide a bug.
Is there a bug that is preventing these fields from being initialized to the
correct values, are these fields being used when they shouldn't be, etc...

- Eric

  reply	other threads:[~2020-09-16  5:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16  5:26 Anant Thazhemadam
2020-09-16  5:41 ` Eric Biggers [this message]
2020-09-17  0:22   ` Al Viro
2020-09-19 14:44     ` [Linux-kernel-mentees] " Greg KH
2020-09-19 16:17       ` Al Viro
2020-09-19 16:55         ` Al Viro
2020-09-19 11:33           ` Anant Thazhemadam
2020-09-19 20:17             ` Anant Thazhemadam
2020-10-04 15:25               ` Anant Thazhemadam
2020-09-16  6:16 ` Greg KH

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200916054157.GC825@sol.localdomain \
    --to=ebiggers@kernel.org \
    --cc=anant.thazhemadam@gmail.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel-mentees@lists.linuxfoundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: [PATCH] fs: fix KMSAN uninit-value bug by initializing nd in do_file_open_root' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).