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authorKP Singh <kpsingh@google.com>2020-11-17 23:29:28 +0000
committerDaniel Borkmann <daniel@iogearbox.net>2020-11-18 01:36:27 +0100
commit3f6719c7b62f0327c9091e26d0da10e65668229e (patch)
treed4552b1b12239b67d9a7a78cd6e0af42a3c3f79b /kernel
parentcbf398d76534427877e5824dd61611514cf284b3 (diff)
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bpf: Add bpf_bprm_opts_set helper
The helper allows modification of certain bits on the linux_binprm struct starting with the secureexec bit which can be updated using the BPF_F_BPRM_SECUREEXEC flag. secureexec can be set by the LSM for privilege gaining executions to set the AT_SECURE auxv for glibc. When set, the dynamic linker disables the use of certain environment variables (like LD_PRELOAD). Signed-off-by: KP Singh <kpsingh@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20201117232929.2156341-1-kpsingh@chromium.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/bpf_lsm.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 553107f4706a..b4f27a874092 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -7,6 +7,7 @@
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/btf.h>
+#include <linux/binfmts.h>
#include <linux/lsm_hooks.h>
#include <linux/bpf_lsm.h>
#include <linux/kallsyms.h>
@@ -51,6 +52,29 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog,
return 0;
}
+/* Mask for all the currently supported BPRM option flags */
+#define BPF_F_BRPM_OPTS_MASK BPF_F_BPRM_SECUREEXEC
+
+BPF_CALL_2(bpf_bprm_opts_set, struct linux_binprm *, bprm, u64, flags)
+{
+ if (flags & ~BPF_F_BRPM_OPTS_MASK)
+ return -EINVAL;
+
+ bprm->secureexec = (flags & BPF_F_BPRM_SECUREEXEC);
+ return 0;
+}
+
+BTF_ID_LIST_SINGLE(bpf_bprm_opts_set_btf_ids, struct, linux_binprm)
+
+const static struct bpf_func_proto bpf_bprm_opts_set_proto = {
+ .func = bpf_bprm_opts_set,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_btf_id = &bpf_bprm_opts_set_btf_ids[0],
+ .arg2_type = ARG_ANYTHING,
+};
+
static const struct bpf_func_proto *
bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -71,6 +95,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_task_storage_get_proto;
case BPF_FUNC_task_storage_delete:
return &bpf_task_storage_delete_proto;
+ case BPF_FUNC_bprm_opts_set:
+ return &bpf_bprm_opts_set_proto;
default:
return tracing_prog_func_proto(func_id, prog);
}