Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix memleak due to fentry attach failure
If it fails to attach fentry, the allocated bpf trampoline image will be left in the system. That can be verified by checking /proc/kallsyms.
This meamleak can be verified by a simple bpf program as follows:
SEC(“fentry/trap_init”) int fentry_run() { return 0; }
It will fail to attach trap_init because this function is freed after kernel init, and then we can find the trampoline image is left in the system by checking /proc/kallsyms.
$ tail /proc/kallsyms ffffffffc0613000 t bpf_trampoline_6442453466_1 [bpf] ffffffffc06c3000 t bpf_trampoline_6442453466_1 [bpf]
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep “FUNC ’trap_init’” [2522] FUNC ’trap_init’ type_id=119 linkage=static
$ echo $((6442453466 & 0x7fffffff)) 2522
Note that there are two left bpf trampoline images, that is because the libbpf will fallback to raw tracepoint if -EINVAL is returned.
Details
- Affected product:
- AlmaLinux 9.2 ESU , TuxCare 9.6 ESU
- Affected packages:
- kernel @ 5.14.0 (+1 more)
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix memleak due to fentry attach failure
If it fails to attach fentry, the allocated bpf trampoline image will be left in the system. That can be verified by checking /proc/kallsyms.
This meamleak can be verified by a simple bpf program as follows:
SEC(“fentry/trap_init”) int fentry_run() { return 0; }
It will fail to attach trap_init because this function is freed after kernel init, and then we can find the trampoline image is left in the system by checking /proc/kallsyms.
$ tail /proc/kallsyms ffffffffc0613000 t bpf_trampoline_6442453466_1 [bpf] ffffffffc06c3000 t bpf_trampoline_6442453466_1 [bpf]
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep “FUNC ’trap_init’” [2522] FUNC ’trap_init’ type_id=119 linkage=static
$ echo $((6442453466 & 0x7fffffff)) 2522
Note that there are two left bpf trampoline images, that is because the libbpf will fallback to raw tracepoint if -EINVAL is returned.