Re: [PATCH] xfs: check the return value of krealloc() in xfs_uuid_mount

[Qinglang Miao]

在 2020/11/25 23:55, Eric Sandeen 写道:
> On 11/25/20 12:50 AM, Qinglang Miao wrote:
> > krealloc() may fail to expand the memory space.
>
> Even with __GFP_NOFAIL?
>
>    * ``GFP_KERNEL | __GFP_NOFAIL`` - overrides the default allocator behavior
>      and all allocation requests will loop endlessly until they succeed.
>      This might be really dangerous especially for larger orders.
>
> > Add sanity checks to it,
> > and WARN() if that really happened.
>
> As aside, there is no WARN added in this patch for a memory failure.
>
> > Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
> > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > Signed-off-by: Qinglang Miao <miaoqinglang@xxxxxxxxxx>
> > ---
> >   fs/xfs/xfs_mount.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > index 150ee5cb8..c07f48c32 100644
> > --- a/fs/xfs/xfs_mount.c
> > +++ b/fs/xfs/xfs_mount.c
> > @@ -80,9 +80,13 @@ xfs_uuid_mount(
> >   	}
> >   
> >   	if (hole < 0) {
> > -		xfs_uuid_table = krealloc(xfs_uuid_table,
> > +		uuid_t *if_xfs_uuid_table;
> > +		if_xfs_uuid_table = krealloc(xfs_uuid_table,
> >   			(xfs_uuid_table_size + 1) * sizeof(*xfs_uuid_table),
> >   			GFP_KERNEL | __GFP_NOFAIL);
> > +		if (!if_xfs_uuid_table)
> > +			goto out_duplicate;
>
> And this would emit "Filesystem has duplicate UUID" which is not correct.
>
> But anyway, the __GFP_NOFAIL in the call makes this all moot AFAICT.
>
> -Eric
Hi Eric,

Sorry for neglecting __GFP_NOFAIL symbol, and I would add a WARN in 
memory failure next time.

Thanks for your advice！
> > +		xfs_uuid_table = if_xfs_uuid_table;
> >   		hole = xfs_uuid_table_size++;
> >   	}
> >   	xfs_uuid_table[hole] = *uuid;
> .