From: Jerome Marchand Date: Thu, 19 Jun 2025 14:06:02 +0000 (+0200) Subject: bpf: Specify access type of bpf_sysctl_get_name args X-Git-Tag: v6.16-rc4~28^2~2^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2eb7648558a7911f2208e8940cd22ca40e93cc76;p=thirdparty%2Flinux.git bpf: Specify access type of bpf_sysctl_get_name args The second argument of bpf_sysctl_get_name() helper is a pointer to a buffer that is being written to. However that isn't specify in the prototype. Until commit 37cce22dbd51a ("bpf: verifier: Refactor helper access type tracking"), all helper accesses were considered as a possible write access by the verifier, so no big harm was done. However, since then, the verifier might make wrong asssumption about the content of that address which might lead it to make faulty optimizations (such as removing code that was wrongly labeled dead). This is what happens in test_sysctl selftest to the tests related to sysctl_get_name. Add MEM_WRITE flag the second argument of bpf_sysctl_get_name(). Signed-off-by: Jerome Marchand Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20250619140603.148942-2-jmarchan@redhat.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 9122c39870bf..f4885514f007 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -2134,7 +2134,7 @@ static const struct bpf_func_proto bpf_sysctl_get_name_proto = { .gpl_only = false, .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_CTX, - .arg2_type = ARG_PTR_TO_MEM, + .arg2_type = ARG_PTR_TO_MEM | MEM_WRITE, .arg3_type = ARG_CONST_SIZE, .arg4_type = ARG_ANYTHING, };