REDHAT-BUG-2265648: Null Pointer Dereference
bpf: Fix re-attachment branch in bpftracingprogattach
The following case can cause a crash due to missing attachbtf:
1) load rawtp program 2) load fentry program with rawtp as targetfd 3) create tracing link for fentry program with targetfd = 0 4) repeat 3
In the end we have:
- prog->aux->dsttrampoline == NULL - tgtprog == NULL (because we did not provide targetfd to linkcreate) - prog->aux->attachbtf == NULL (the program was loaded with attachprogfd=X) - the program was loaded for tgtprog but we have no way to find out which one
BUG: kernel NULL pointer dereference, address: 0000000000000058 Call Trace: <TASK> ? die+0x20/0x70 ? pagefaultoops+0x15b/0x430 ? fixupexception+0x22/0x330 ? excpagefault+0x6f/0x170 ? asmexcpagefault+0x22/0x30 ? bpftracingprogattach+0x279/0x560 ? btfobjid+0x5/0x10 bpftracingprogattach+0x439/0x560 sysbpf+0x1cf4/0x2de0 x64sysbpf+0x1c/0x30 dosyscall64+0x41/0xf0 entrySYSCALL64afterhwframe+0x6e/0x76
Return -EINVAL in this situation.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Linux kernelto a version that resolves this vulnerability.Patch bpf: Fix re-attachment branch in bpf_tracing_prog_attach - Compensating control
Avoid triggering the crash by not using the bpf tracing re-attachment path when the program would have missing aux fields (e.g., ensure the program is not loaded in a way that results in missing attach_btf / prog->aux->attach_btf == NULL and dst_trampoline == NULL). Return -EINVAL in this situation rather than attempting re-attachment/link creation.