Chirantan Ekbote 814a8da0ed devices: fs: Use 2 stage create and mkdir ... 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>		2020-06-04 12:49:49 +00:00
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9p_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
balloon_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
block_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
common_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
cras_audio_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
fs_device.policy	devices: fs: Use 2 stage create and mkdir	2020-06-04 12:49:49 +00:00
gpu_device.policy	seccomp: gpu: allow sysinfo	2020-04-24 16:02:12 +00:00
input_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
net_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
null_audio_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
pmem_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
rng_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
serial.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
tpm_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
vhost_net_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
vhost_vsock_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
wl_device.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00
xhci.policy	seccomp: remove redundant unconditional arm/arm64 rules	2020-02-04 23:27:21 +00:00