When creating a file or directory the virtio-fs server changes its
effective uid and gid to the uid and gid of the process that made the
call. This ensures that the file or directory has the correct owner and
group when it is created and also serves as an access check to ensure
that the process that made the call has permission to modify the parent
directory.
However, this causes an EACCES error when the following conditions are
met:
* The parent directory has g+rw permissions with gid A
* The process has gid B but has A in its list of supplementary groups
In this case the fuse context only contains gid B, which doesn't have
permission to modify the parent directory.
Unfortunately there's no way for us to detect this on the server side so
instead we just have to rely on the permission checks carried out by the
kernel driver. If the server receives a create call, then assume that
the kernel has verified that the process is allowed to create that
file/directory and just create it without changing the server thread's
uid and gid.
Additionally, in order to ensure that a newly created file appears
atomically in the parent directory with the proper owner and group,
change the create implementation to use `O_TMPFILE` and `linkat` as
described in the open(2) manpage. There is no `O_TMPFILE` equivalent
for directories so create a "hidden" directory with a randomly generated
name, modify the uid/gid and mode, and then rename it into place.
BUG=b:156696212
TEST=tast run $DUT vm.Virtiofs
TEST=Create a test directory with group wayland and permissions g+rw.
Then run `su -s /bin/bash -c 'touch ${dir}/foo' - crosvm` and
`su -s /bin/bash -c 'mkdir ${dir}/bar' - crosvm`.
Change-Id: If5fbcb1b011664c7c1ac29542a2f90d129c34962
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2217534
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: Chirantan Ekbote <chirantan@chromium.org>
Using the `open_inode` method on an fd for a symlink results in the
kernel returning -ELOOP. Since there are no `*at` methods for extended
attributes, manually read the path for the file and then use the
l{get,set,list,remove}xattr method on the returned path.
BUG=b:136128512
TEST=boot arcvm with virtio-fs and selinux enabled
Change-Id: I2fde57db8a075838a3a877309f6cf89059f19258
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2120763
Auto-Submit: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Minijail's policy compiler complains when there's multiple
unconditional rules for a syscall. In most cases the rules
are redundant to common_device.policy.
BUG=None
TEST=Ran compile_seccomp_policy.py until it stopped
complaining.
Change-Id: Ic43d1fd13f9c012641d71e526942229eb8b08ed4
Signed-off-by: Matt Delco <delco@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2034024
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
This is used in Rust 1.40.0's libstd in place of stat/fstat; update the
whitelists to allow the new syscall as well.
BUG=chromium:1042461
TEST=`crosvm disk resize` does not trigger seccomp failure
Change-Id: Ia3f0e49ee009547295c7af7412dfb5eb3ac1efcb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2003685
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
Add support for FS_IOC_{GET,SET}_ENCRYPTION_POLICY. Unfortunately,
since the I/O direction is encoded backwards in the ioctl definitions,
these will only work with on a kernel that's compiled with a patch to
mark them as unrestricted FUSE ioctls.
BUG=b:136127632
TEST=Compile and run the vfs_crypto.c program on a virtio-fs mount
inside a VM
Change-Id: I124c5a943111b453dd44921a079a2baa1036dfd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1952570
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
The setres{u,g}id and the gete{u,g}id system calls on arm use 16 bit
values for uid_t and gid_t. This causes the kernel to interpret a
uid/gid of 65535 as -1, which means do nothing.
Use the 32-bit variants of these system calls instead so that we can use
32-bit values. Normally, libc would take care of hiding these kinds of
implementation details but since we can't use the libc wrappers for
these system calls, we have to do it ourselves.
BUG=b:136128319
TEST=`tast run vm.Virtiofs` on kevin
Change-Id: I6c0fda42c131e059139000828b3a53d4a73f340c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1923569
Tested-by: Chirantan Ekbote <chirantan@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Add x86_64 and arm seccomp policy files for the virtio-fs device.
BUG=b:136128319
TEST=Run a vm with a sandboxed virtio-fs device
Change-Id: I8ea7c5d3e90696077f0c2b1f942cb286a0b36cf4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1916559
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>
