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* FAILED: patch "[PATCH] ovl: fix missing negative dentry check in ovl_rename()" failed to apply to 4.4-stable tree
@ 2021-10-09 13:55 gregkh
  2021-10-22  0:16 ` [PATCH] ovl: fix missing negative dentry check in ovl_rename() Masami Ichikawa(CIP)
  0 siblings, 1 reply; 3+ messages in thread
From: gregkh @ 2021-10-09 13:55 UTC (permalink / raw)
  To: zhengliang6, mszeredi, stable; +Cc: stable


The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a295aef603e109a47af355477326bd41151765b6 Mon Sep 17 00:00:00 2001
From: Zheng Liang <zhengliang6@huawei.com>
Date: Fri, 24 Sep 2021 09:16:27 +0800
Subject: [PATCH] ovl: fix missing negative dentry check in ovl_rename()

The following reproducer

  mkdir lower upper work merge
  touch lower/old
  touch lower/new
  mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
  rm merge/new
  mv merge/old merge/new & unlink upper/new

may result in this race:

PROCESS A:
  rename("merge/old", "merge/new");
  overwrite=true,ovl_lower_positive(old)=true,
  ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE

PROCESS B:
  unlink("upper/new");

PROCESS A:
  lookup newdentry in new_upperdir
  call vfs_rename() with negative newdentry and RENAME_EXCHANGE

Fix by adding the missing check for negative newdentry.

Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc: <stable@vger.kernel.org> # v3.18
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1fefb2b8960e..93c7c267de93 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1219,9 +1219,13 @@ static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir,
 				goto out_dput;
 		}
 	} else {
-		if (!d_is_negative(newdentry) &&
-		    (!new_opaque || !ovl_is_whiteout(newdentry)))
-			goto out_dput;
+		if (!d_is_negative(newdentry)) {
+			if (!new_opaque || !ovl_is_whiteout(newdentry))
+				goto out_dput;
+		} else {
+			if (flags & RENAME_EXCHANGE)
+				goto out_dput;
+		}
 	}
 
 	if (olddentry == trap)


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* [PATCH] ovl: fix missing negative dentry check in ovl_rename()
  2021-10-09 13:55 FAILED: patch "[PATCH] ovl: fix missing negative dentry check in ovl_rename()" failed to apply to 4.4-stable tree gregkh
@ 2021-10-22  0:16 ` Masami Ichikawa(CIP)
  2021-10-24 11:50   ` Greg KH
  0 siblings, 1 reply; 3+ messages in thread
From: Masami Ichikawa(CIP) @ 2021-10-22  0:16 UTC (permalink / raw)
  To: gregkh; +Cc: mszeredi, stable, zhengliang6, Masami Ichikawa

From: Zheng Liang <zhengliang6@huawei.com>

From: Zheng Liang <zhengliang6@huawei.com>

commit a295aef603e109a47af355477326bd41151765b6 upstream.

The following reproducer

  mkdir lower upper work merge
  touch lower/old
  touch lower/new
  mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
  rm merge/new
  mv merge/old merge/new & unlink upper/new

may result in this race:

PROCESS A:
  rename("merge/old", "merge/new");
  overwrite=true,ovl_lower_positive(old)=true,
  ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE

PROCESS B:
  unlink("upper/new");

PROCESS A:
  lookup newdentry in new_upperdir
  call vfs_rename() with negative newdentry and RENAME_EXCHANGE

Fix by adding the missing check for negative newdentry.

Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Fixes: e9be9d5e76e3 ("overlay filesystem")
Cc: <stable@vger.kernel.org> # v3.18
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reference: CVE-2021-20321
Signed-off-by: Masami Ichikawa(CIP) <masami.ichikawa@cybertrust.co.jp>
---
 fs/overlayfs/dir.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index eedacae889b9..80bf0ab52e81 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -824,9 +824,13 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
 		}
 	} else {
 		new_create = true;
-		if (!d_is_negative(newdentry) &&
-		    (!new_opaque || !ovl_is_whiteout(newdentry)))
-			goto out_dput;
+		if (!d_is_negative(newdentry)) {
+			if (!new_opaque || !ovl_is_whiteout(newdentry))
+				goto out_dput;
+		} else {
+			if (flags & RENAME_EXCHANGE)
+				goto out_dput;
+		}
 	}
 
 	if (olddentry == trap)
-- 
2.33.0


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] ovl: fix missing negative dentry check in ovl_rename()
  2021-10-22  0:16 ` [PATCH] ovl: fix missing negative dentry check in ovl_rename() Masami Ichikawa(CIP)
@ 2021-10-24 11:50   ` Greg KH
  0 siblings, 0 replies; 3+ messages in thread
From: Greg KH @ 2021-10-24 11:50 UTC (permalink / raw)
  To: Masami Ichikawa(CIP); +Cc: mszeredi, stable, zhengliang6, Masami Ichikawa

On Fri, Oct 22, 2021 at 09:16:05AM +0900, Masami Ichikawa(CIP) wrote:
> From: Zheng Liang <zhengliang6@huawei.com>
> 
> From: Zheng Liang <zhengliang6@huawei.com>
> 
> commit a295aef603e109a47af355477326bd41151765b6 upstream.
> 
> The following reproducer
> 
>   mkdir lower upper work merge
>   touch lower/old
>   touch lower/new
>   mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
>   rm merge/new
>   mv merge/old merge/new & unlink upper/new
> 
> may result in this race:
> 
> PROCESS A:
>   rename("merge/old", "merge/new");
>   overwrite=true,ovl_lower_positive(old)=true,
>   ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE
> 
> PROCESS B:
>   unlink("upper/new");
> 
> PROCESS A:
>   lookup newdentry in new_upperdir
>   call vfs_rename() with negative newdentry and RENAME_EXCHANGE
> 
> Fix by adding the missing check for negative newdentry.
> 
> Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
> Fixes: e9be9d5e76e3 ("overlay filesystem")
> Cc: <stable@vger.kernel.org> # v3.18
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> Reference: CVE-2021-20321
> Signed-off-by: Masami Ichikawa(CIP) <masami.ichikawa@cybertrust.co.jp>
> ---
>  fs/overlayfs/dir.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index eedacae889b9..80bf0ab52e81 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -824,9 +824,13 @@ static int ovl_rename2(struct inode *olddir, struct dentry *old,
>  		}
>  	} else {
>  		new_create = true;
> -		if (!d_is_negative(newdentry) &&
> -		    (!new_opaque || !ovl_is_whiteout(newdentry)))
> -			goto out_dput;
> +		if (!d_is_negative(newdentry)) {
> +			if (!new_opaque || !ovl_is_whiteout(newdentry))
> +				goto out_dput;
> +		} else {
> +			if (flags & RENAME_EXCHANGE)
> +				goto out_dput;
> +		}
>  	}
>  
>  	if (olddentry == trap)
> -- 
> 2.33.0
> 

Now queued up for 4.4.y, thanks!

greg k-h

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-10-24 11:50 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-09 13:55 FAILED: patch "[PATCH] ovl: fix missing negative dentry check in ovl_rename()" failed to apply to 4.4-stable tree gregkh
2021-10-22  0:16 ` [PATCH] ovl: fix missing negative dentry check in ovl_rename() Masami Ichikawa(CIP)
2021-10-24 11:50   ` Greg KH

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