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Re: [PATCH] virtiofsd: Disable killpriv_v2 by default
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH] virtiofsd: Disable killpriv_v2 by default |
Date: |
Tue, 2 Aug 2022 14:57:01 +0100 |
User-agent: |
Mutt/2.2.6 (2022-06-05) |
* Vivek Goyal (vgoyal@redhat.com) wrote:
> We are having bunch of issues with killpriv_v2 enabled by default. First
> of all it relies on clearing suid/sgid bits as needed by dropping
> capability CAP_FSETID. This does not work for remote filesystems like
> NFS (and possibly others).
>
> Secondly, we are noticing other issues related to clearing of SGID
> which leads to failures for xfstests generic/355 and generic/193.
>
> Thirdly, there are other issues w.r.t caching of metadata (suid/sgid)
> bits in fuse client with killpriv_v2 enabled. Guest can cache that
> data for sometime even if cleared on server.
>
> Second and Third issue are fixable. Just that it might take a little
> while to get it fixed in kernel. First one will probably not see
> any movement for a long time.
>
> Given these issues, killpriv_v2 does not seem to be a good candidate
> for enabling by default. We have already disabled it by default in
> rust version of virtiofsd.
>
> Hence this patch disabled killpriv_v2 by default. User can choose to
> enable it by passing option "-o killpriv_v2".
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Queued
> ---
> tools/virtiofsd/passthrough_ll.c | 13 ++-----------
> 1 file changed, 2 insertions(+), 11 deletions(-)
>
> Index: rhvgoyal-qemu/tools/virtiofsd/passthrough_ll.c
> ===================================================================
> --- rhvgoyal-qemu.orig/tools/virtiofsd/passthrough_ll.c 2022-07-29
> 08:19:05.925119947 -0400
> +++ rhvgoyal-qemu/tools/virtiofsd/passthrough_ll.c 2022-07-29
> 08:27:08.048049096 -0400
> @@ -767,19 +767,10 @@ static void lo_init(void *userdata, stru
> fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling killpriv_v2\n");
> conn->want |= FUSE_CAP_HANDLE_KILLPRIV_V2;
> lo->killpriv_v2 = 1;
> - } else if (lo->user_killpriv_v2 == -1 &&
> - conn->capable & FUSE_CAP_HANDLE_KILLPRIV_V2) {
> - /*
> - * User did not specify a value for killpriv_v2. By default enable it
> - * if connection offers this capability
> - */
> - fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling killpriv_v2\n");
> - conn->want |= FUSE_CAP_HANDLE_KILLPRIV_V2;
> - lo->killpriv_v2 = 1;
> } else {
> /*
> - * Either user specified to disable killpriv_v2, or connection does
> - * not offer this capability. Disable killpriv_v2 in both the cases
> + * Either user specified to disable killpriv_v2, or did not
> + * specify anything. Disable killpriv_v2 in both the cases.
> */
> fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling killpriv_v2\n");
> conn->want &= ~FUSE_CAP_HANDLE_KILLPRIV_V2;
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK