p9fs: Fix creating files with restrictive permissions

When a file is created via p9fs with restrictive permissions (like 000),
the 9P TCREATE request successfully creates and natively opens the file

p9fs: Fix creating files with restrictive permissions

When a file is created via p9fs with restrictive permissions (like 000),
the 9P TCREATE request successfully creates and natively opens the file,
returning an open, writable file descriptor. Previously, p9fs would
attempt a subsequent TOPEN. That TOPEN would fail with EACCES due to the
restrictive mode, leaving a 0-byte file and causing operations like 'mv'
to abort.

We now preserve the writable descriptor returned by TCREATE so that the
subsequent VOP_OPEN can use it directly, avoiding the failing TOPEN.
Additionally, p9fs_compatible_mode now appropriately isolates the base
access intent when matching fids, preventing extended flags from
breaking the match.

A test case for this behavior has been submitted to pjdfstest:
https://github.com/pjd/pjdfstest/pull/87

Resolves: https://github.com/CTSRD-CHERI/cheribsd/issues/2617

Reviewed by: markj
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D56494

show more ...

p9fs: implement basic pathconf support

This is needed for various pjdfstest tests which fail with syntax errors
if pathconf _PC_NAME_MAX/_PC_PATH_MAX return -1. For NAME_MAX we can use
the 9P2000.L

p9fs: implement basic pathconf support

This is needed for various pjdfstest tests which fail with syntax errors
if pathconf _PC_NAME_MAX/_PC_PATH_MAX return -1. For NAME_MAX we can use
the 9P2000.L Tstatfs call to get namelen from the host. While this could
theoretically be different for nested filesystems in the shared mount it
is a much better guess than just returning 255.
There does not seem to be a way to get the host PATH_MAX, so we just
return the conservative kernel default.

Found while fixing https://github.com/CTSRD-CHERI/cheribsd/issues/2617.

Reviewed by: markj, kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D56493

show more ...

p9fs: Move UMA zone initialization to VFS module lifecycle

Previously, the UMA zones required for 9P requests (p9fs_buf_zone,
p9fs_req_zone, etc.) were initialized and destroyed in the
virtio_p9fs t

p9fs: Move UMA zone initialization to VFS module lifecycle

Previously, the UMA zones required for 9P requests (p9fs_buf_zone,
p9fs_req_zone, etc.) were initialized and destroyed in the
virtio_p9fs transport module. This caused issues when unloading
the core p9fs module.

This change moves p9_init_zones() and p9_destroy_zones() into
p9fs_init() and p9fs_uninit() inside p9fs_vfsops.c so that they
are correctly bound to the VFS filesystem module lifecycle via
vfs_modevent, aligning p9fs with standard FreeBSD VFS semantics.

Found while fixing https://github.com/CTSRD-CHERI/cheribsd/issues/2617.

Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D56492

show more ...