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In-Reply-To: <bf90de00-4d6a-4440-b6a1-42ac9e358158@moroto.mountain>
From: Steve French <smfrench@gmail.com>
Date: Thu, 1 Feb 2024 12:03:43 -0600
Message-ID: <CAH2r5mv-HdiM2zasyq1F-LN=kqD93EfKf+UMcnR+0_GNv3xB2Q@mail.gmail.com>
Subject: Re: [PATCH] smb: client: Fix a double lock bug in smb2_reconnect()
To: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Shyam Prasad N <sprasad@microsoft.com>, Steve French <sfrench@samba.org>, 
	Paulo Alcantara <pc@manguebit.com>, Ronnie Sahlberg <ronniesahlberg@gmail.com>, Tom Talpey <tom@talpey.com>, 
	linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org, 
	kernel-janitors@vger.kernel.org
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This (and a loosely related problem   were already fixed in an updated
version of that patch (updated in cifs-2.6.git for-next yesterday);
https://git.samba.org/?p=3Dsfrench/cifs-2.6.git;a=3Dcommit;h=3Dee36a3b345c4=
33a846effcdcfba437c2298eeda5


On Thu, Feb 1, 2024 at 6:19=E2=80=AFAM Dan Carpenter <dan.carpenter@linaro.=
org> wrote:
>
> This goto will try to lock spin_lock(&ses->ses_lock) twice which will
> lead to a deadlock.
>
> Fixes: 17525952fa83 ("cifs: make sure that channel scaling is done only o=
nce")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
>  fs/smb/client/smb2pdu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
> index 2837fc4465a7..dcd3f6f08c7f 100644
> --- a/fs/smb/client/smb2pdu.c
> +++ b/fs/smb/client/smb2pdu.c
> @@ -401,7 +401,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon =
*tcon,
>
>         spin_lock(&ses->ses_lock);
>         if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS)
> -               goto skip_add_channels;
> +               goto skip_add_channels_locked;
>         ses->flags |=3D CIFS_SES_FLAG_SCALE_CHANNELS;
>         spin_unlock(&ses->ses_lock);
>
> @@ -448,6 +448,7 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon =
*tcon,
>
>  skip_add_channels:
>         spin_lock(&ses->ses_lock);
> +skip_add_channels_locked:
>         ses->flags &=3D ~CIFS_SES_FLAG_SCALE_CHANNELS;
>         spin_unlock(&ses->ses_lock);
>
> --
> 2.43.0
>
>


--=20
Thanks,

Steve