If, when init'ing cgroups for a container start, we detect that we
are an unprivileged user on a unified-hierarchy-only system, then we
try to request systemd, through dbus api, to create a new scope for
us with delegation. Call the cgroup it creates for us P1. We then
create P1/init, move ourselves into there, so we can enable the
controllers for delegation to P1's children through P1/cgroup.subtree_control.
On attach, we try to request systemd attach us to the container's
scope. We can't do that ourselves in the normal case, as root owns
our login cgroups.
Create a new command api for the lxc monitor to tell lxc-attach the
systemd scope to which to attach.
Changelog:
* free cgroup_meta.systemd_scope in lxc_conf_free (Thanks Tycho)
* fix some indent
* address some (not all) of brauner's feedback
Signed-off-by: Serge Hallyn <serge@hallyn.com>
fuzz-lxc-cgroup-init currently fails for me with the input
```
lxc.cap.keep=0
```
with this report:
```
==640655==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x833c77 in parse_cap /src/lxc/san_build/../src/lxc/conf.c:3161:6
#1 0xaa5fd6 in add_cap_entry /src/lxc/san_build/../src/lxc/confile.c:2462:9
#2 0x9eb69c in set_config_cap_keep /src/lxc/san_build/../src/lxc/confile.c:2503:8
#3 0x974a76 in parse_line /src/lxc/san_build/../src/lxc/confile.c:3115:9
#4 0xea8cac in lxc_file_for_each_line_mmap /src/lxc/san_build/../src/lxc/parse.c:123:9
#5 0x9700a1 in lxc_config_read /src/lxc/san_build/../src/lxc/confile.c:3192:9
#6 0x4a3b50 in LLVMFuzzerTestOneInput /src/lxc/san_build/../src/tests/fuzz-lxc-cgroup-init.c:40:8
#7 0x10556e3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:611:15
#8 0x1041372 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:324:6
#9 0x1046bbc in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:860:9
#10 0x106f7b2 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
#11 0x7ffff7bc00b2 in __libc_start_main /build/glibc-sMfBJT/glibc-2.31/csu/../csu/libc-start.c:308:16
#12 0x420a9d in _start (/home/fuzzer/oss-fuzz/build/out/lxc/fuzz-lxc-cgroup-init+0x420a9d)
Uninitialized value was created by an allocation of 'last_cap' in the stack frame of function 'parse_cap'
#0 0x832e30 in parse_cap /src/lxc/san_build/../src/lxc/conf.c:3131
```
The reason is that without libcap we parse_cap ends up comparing two
uninitialized values. See the snippet below:
```
int parse_cap(const char *cap_name, __u32 *cap)
{
int ret;
unsigned int res;
__u32 last_cap;
[...]
ret = lxc_caps_last_cap(&last_cap); // NOTE: 1. Call here.
if (ret) // Not taken as dummy lxc_caps_last_cap returned 0.
return -1;
if ((__u32)res > last_cap) // last_cap is uninitialized.
return -1;
*cap = (__u32)res;
return 0;
}
```
Root cause seems to be that the dummy `lxc_caps_last_cap` returns 0 but
doesn't set the last_cap value. This patch just returns -1 as an error code
to avoid the uninitialized read.
Note: When reproducing the bug you need to compile with O0 and *not* with O1
otherwise you will not see the report.
Signed-off-by: Raphael Isemann <teemperor@gmail.com>
In order to compile for fuzzers where we will need and want to turn a
bunch of things off add command line switches that allow us to do so.
Signed-off-by: Christian Brauner (Microsoft) <christian.brauner@ubuntu.com>
The old split didn't buy us a lot and causes problems when buidling with
sanitizers enabled so just use the full sources.
Signed-off-by: Christian Brauner (Microsoft) <christian.brauner@ubuntu.com>
