Assertion `cgroup_path_relative_to_mount[common_path_prefix_len] == '/'' failed #34287
Description
I have been trying to add cgroupv2 support to coreclr and ran into this assertion. I have a test a program that #includes cgroup.cpp and then calls various cgroup methods in it.
#include "cgroup.cpp"
int main(int, char *[])
{
InitializeCGroup();
printf("initialized cgroup\n");
size_t physical_memory_limit = GetRestrictedPhysicalMemoryLimit();
printf("GetResitrictedPhysicalMemoryLimit: %lu\n", physical_memory_limit);
size_t used_memory = 0;
bool okay_memory_used = GetPhysicalMemoryUsed(&used_memory);
printf("GetPhysicalMemoryUsed: %d %lu\n", okay_memory_used, used_memory);
uint32_t cpu_limit = 0;
bool okay_cpu_limit = GetCpuLimit(&cpu_limit);
printf("GetCpuLimit: %d %u\n", okay_cpu_limit, cpu_limit);
CleanupCGroup();
printf("cleaned up cgroups\n");
return 0;
}I am running Fedora 31, with cgroupv1 (using systemd.unified_cgroup_hierarchy=0 kernel command line) and podman. This program crashes when run inside a container:
cg: cgroup.cpp:192: static char* CGroup::FindCgroupPath(bool (*)(const char*)): Assertion `cgroup_path_relative_to_mount[common_path_prefix_len] == '/'' failed.
Program received signal SIGABRT, Aborted.
0x00007fb062a41625 in raise () from /lib64/libc.so.6
Missing separate debuginfos, use: dnf debuginfo-install libgcc-9.2.1-1.fc31.x86_64 libstdc++-9.2.1-1.fc31.x86_64
(gdb) bt
#0 0x00007fb062a41625 in raise () from /lib64/libc.so.6
#1 0x00007fb062a2a8d9 in abort () from /lib64/libc.so.6
#2 0x00007fb062a2a7a9 in __assert_fail_base.cold () from /lib64/libc.so.6
#3 0x00007fb062a39a66 in __assert_fail () from /lib64/libc.so.6
#4 0x0000000000401a4e in CGroup::FindCgroupPath (is_subsystem=0x4018dc <CGroup::IsMemorySubsystem(char const*)>) at cgroup.cpp:192
#5 0x00000000004015b4 in CGroup::Initialize () at cgroup.cpp:50
#6 0x000000000040126f in InitializeCGroup () at cgroup.cpp:456
#7 0x00000000004014fc in main () at cg.cpp:7
(gdb) frame 4
#4 0x0000000000401a4e in CGroup::FindCgroupPath (is_subsystem=0x4018dc <CGroup::IsMemorySubsystem(char const*)>) at cgroup.cpp:192
192 assert(cgroup_path_relative_to_mount[common_path_prefix_len] == '/');
(gdb) p common_path_prefix_len
$1 = 92
(gdb) p hierarchy_mount
$2 = 0x2031bf0 "/sys/fs/cgroup/memory"
(gdb) p hierarchy_root
$3 = 0x2031e30 "/machine.slice/libpod-8ec162730bf476f53bbbb9406b232f479fee5434c5ae08a939e7dbcd1a7283aa.scope"
(gdb) p cgroup_path_relative_to_mount
$4 = 0x2032100 "/machine.slice/libpod-8ec162730bf476f53bbbb9406b232f479fee5434c5ae08a939e7dbcd1a7283aa.scope"
(gdb) p cgroup_path_relative_to_mount[92]
$5 = 0 '\000'
This seems to have been introduced by #980
Seems to me like the code just expects a trailing slash that's not present:
common_path_prefix_len = strlen(hierarchy_root);
if ((common_path_prefix_len == 1) || strncmp(hierarchy_root, cgroup_path_relative_to_mount, common_path_prefix_len) != 0)
{
common_path_prefix_len = 0;
}
assert(cgroup_path_relative_to_mount[common_path_prefix_len] == '/');
strcat(cgroup_path, cgroup_path_relative_to_mount + common_path_prefix_len);A fix might be as simple as generalizing the assert to handle the case where cgroup_path_relative_to_mount[common_path_prefix_len] is NULL.
cc @janvorli