In case we get ENOSYS from openat2(2), this is expected, so log that
we're falling back to using securejoin as debug.
Otherwise, log it as a warning (as the error is unexpected, but we're
still good to go).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In case openat2 is available, it will be used to guarantee
that we're not accessing anything other than cgroupfs[2] files.
In cases when openat2 is not available, or when cgroup has a
non-standard prefix (not "/sys/fs/cgroup", which might theoretically
be the case on some very old installs and/or very custom systems),
fall back to using securejoin + os.Open like we did before.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Move the functionality of opening a cgroup file into a separate
function, OpenFile, which, similar to ReadFile and WriteFile,
use separate dir and file arguments.
Change ReadFile and WriteFile to rely on OpenFile, and use lower-level
read and write instead of ones from ioutil.
It changes the semantics of WriteFile a bit -- it no longer uses
O_CREAT flag. This is good for real cgroup as there is no need to try
creating the files in there, but can potentially break WriteFile users
-- previously, EPERM error was returned for non-existing files, and
now it's ENOENT.
This also breaks the fs/fs2 unit tests since they write to pseudo-cgroup
files inside a test directory (not to a real cgroup fs), and now
fscommon.WriteFile do not create or truncate files, so we have to add a
variable that is set by the unit tests.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This removes package dependency on cgroup, as following commits
make cgroup use fscommon, which would result in dependency cycle.
The code to find out memory cgroup root is not really needed,
as 99% of test envrionments will have it at /sys/fs/cgroup/memory.
If not, that means we're either on cgroupv2 or on some very custom
system, so just skip the test.
The code that checks if we're on cgroupv2 is replaced by the check
of the particular v1 control file.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
1. Use GetCgroupParamString as the initial part of both functions are
the same and we can reuse it. This also gives us whatever security
measures GetCgroupParamString has (see previous commit).
2. Fix the error wrapping to not add the value, as it is already a part
of the error returned by ParseUint.
3. Improve docstring.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
1. Use own ReadFile wrapper instead of ioutils.ReadFile.
This makes it use the security measures of ReadFile.
2. Improve doc.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
2. Fix wrapping the error to not have the value as it's already
part of the error returned from ParseUint.
3. Fix/improve doc.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
As the underlying error message from iotuils.WriteFile already contains
file name, there's no need to put it, otherwise we end up with something
like:
failed to write "val" to "/sys/fs/cgroup/.../file": open /sys/fs/cgroup/.../file: permission denied
With this patch, the error will be
failed to write "val": open /sys/fs/cgroup/.../file: permission denied
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Using errors.Unwrap() is not the best thing to do, since it returns
nil in case of an error which was not wrapped. More to say,
errors package provides more elegant ways to check for underlying
errors, such as errors.As() and errors.Is().
This reverts commit f8e138855d, reversing
changes made to 6ca9d8e6da.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Tested that the EINTR is still being detected:
> $ go1.14 test -c # 1.14 is needed for EINTR to happen
> $ sudo ./fscommon.test
> INFO[0000] interrupted while writing 1063068 to /sys/fs/cgroup/memory/test-eint-89293785/memory.limit_in_bytes
> PASS
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Golang 1.14 introduces asynchronous preemption which results into
applications getting frequent EINTR (syscall interrupted) errors when
invoking slow syscalls, e.g. when writing to cgroup files.
As writing to cgroups is idempotent, it is safe to retry writing to the
file whenever the write syscall is interrupted.
Signed-off-by: Mario Nitchev <marionitchev@gmail.com>
split fs2 package from fs, as mixing up fs and fs2 is very likely to result in
unmaintainable code.
Inspired by containerd/cgroups#109
Fix#2157
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Piotr Wagner