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From: Sabin Rapan <sabin.rapan@gmail.com>
To: Dan Carpenter <dan.carpenter@oracle.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	David Howells <dhowells@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] vfs: namespace: error pointer dereference in do_remount()
Date: Mon, 24 Sep 2018 09:10:26 +0300	[thread overview]
Message-ID: <1c94b8cc-44df-d837-f07b-2d7186117a21@gmail.com> (raw)
In-Reply-To: <20180907122534.ojogke2alt3ldbom@kili.mountain>


This patch also fixes the syzbot bug (BUG: unable to handle kernel paging
request in do_mount)
(https://syzkaller.appspot.com/bug?id=611b50e30eb1634e75688903289148fe2a042c1d)

Short description of the syzbot reproducer:
* do_mount() is called with remount flag
* vfs_new_fs_context() is called and tries to allocate a new context
* slab allocation fails due to injected fault
* an invalid context is passed to parse_monolithic_mount_data()
* kernel crash due to invalid pointer access

On 07.09.2018 15:25, Dan Carpenter wrote:
> We need to check if vfs_new_fs_context() returns an error pointer.
> 
> Fixes: fd0002870b45 ("vfs: Implement a filesystem superblock creation/configuration context")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/fs/namespace.c b/fs/namespace.c
> index a240e20093e0..841517520c08 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -2384,6 +2384,8 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags,
>  	fc = vfs_new_fs_context(path->dentry->d_sb->s_type,
>  				path->dentry, sb_flags, MS_RMT_MASK,
>  				FS_CONTEXT_FOR_RECONFIGURE);
> +	if (IS_ERR(fc))
> +		return PTR_ERR(fc);
>  
>  	err = parse_monolithic_mount_data(fc, data, data_size);
>  	if (err < 0)
> 

      reply	other threads:[~2018-09-24 12:11 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-07 12:25 Dan Carpenter
2018-09-24  6:10 ` Sabin Rapan [this message]

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