Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH 27/33] sctp: export sctp_setsockopt_bindx | Date | Sat, 16 May 2020 15:11:40 +0000 |
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From: David Howells > Sent: 15 May 2020 16:20 > Christoph Hellwig <hch@lst.de> wrote: > > > > The advantage on using kernel_setsockopt here is that sctp module will > > > only be loaded if dlm actually creates a SCTP socket. With this > > > change, sctp will be loaded on setups that may not be actually using > > > it. It's a quite big module and might expose the system. > > > > True. Not that the intent is to kill kernel space callers of setsockopt, > > as I plan to remove the set_fs address space override used for it. > > For getsockopt, does it make sense to have the core kernel load optval/optlen > into a buffer before calling the protocol driver? Then the driver need not > see the userspace pointer at all. > > Similar could be done for setsockopt - allocate a buffer of the size requested > by the user inside the kernel and pass it into the driver, then copy the data > back afterwards.
Yes, it also simplifies all the compat code. And there is a BPF test in setsockopt that also wants to pass on a kernel buffer.
I'm willing to sit and write the patch. Quoting from a post I made later on Friday.
Basically:
This patch sequence (to be written) does the following:
Patch 1: Change __sys_setsockopt() to allocate a kernel buffer, copy the data into it then call set_fs(KERNEL_DS). An on-stack buffer (say 64 bytes) will be used for small transfers.
Patch 2: The same for __sys_getsockopt().
Patch 3: Compat setsockopt.
Patch 4: Compat getsockopt.
Patch 5: Remove the user copies from the global socket options code.
Patches 6 to n-1; Remove the user copies from the per-protocol code.
Patch n: Remove the set_fs(KERNEL_DS) from the entry points.
This should be bisectable.
David
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