Re: [PATCH] sunrpc: don't pass on-stack memory to sg_set_buf

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> On Oct 25, 2016, at 14:45, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
> 
> From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
> 
> As of ac4e97abce9b "scatterlist: sg_set_buf() argument must be in linear
> mapping", sg_set_buf hits a BUG when make_checksum_v2->xdr_process_buf,
> among other callers, passes it memory on the stack.
> 
> We only need a scatterlist to pass this to the crypto code, and it seems
> like overkill to require kmalloc'd memory just to encrypt a few bytes,
> but for now this seems the best fix.
> 
> Note many of these callers are in the NFS write paths, so we shouldn't
> really be allocating GFP_KERNEL.  But we already have other allocations
> in these code paths.  A larger redesign may be necessary to allow
> allocations to be done earlier.

NACK…  I agree that there may already be borkage in RPCSEC_GSS-land, but that’s not a reason to be adding to the pile of things that need to be fixed… The allocations that lie in the RPC client’s encode/decode path do need to be GFP_NOFS….

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