tools/virtiofsd/passthrough_ll.c | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-)
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>
---
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;
* 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
* 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> OK, yes I see the corresponding 9b03f65d commit in the Rust version. Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > --- > 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
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