From: Deepanshu Kartikey Date: Wed, 7 Jan 2026 02:10:37 +0000 (+0530) Subject: bpf: Reject BPF_MAP_TYPE_INSN_ARRAY in check_reg_const_str() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9df5fad801c5c568ee5f5dacd8b53565d88e4f02;p=thirdparty%2Flinux.git bpf: Reject BPF_MAP_TYPE_INSN_ARRAY in check_reg_const_str() BPF_MAP_TYPE_INSN_ARRAY maps store instruction pointers in their ips array, not string data. The map_direct_value_addr callback for this map type returns the address of the ips array, which is not suitable for use as a constant string argument. When a BPF program passes a pointer to an insn_array map value as ARG_PTR_TO_CONST_STR (e.g., to bpf_snprintf), the verifier's null-termination check in check_reg_const_str() operates on the wrong memory region, and at runtime bpf_bprintf_prepare() can read out of bounds searching for a null terminator. Reject BPF_MAP_TYPE_INSN_ARRAY in check_reg_const_str() since this map type is not designed to hold string data. Reported-by: syzbot+2c29addf92581b410079@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2c29addf92581b410079 Tested-by: syzbot+2c29addf92581b410079@syzkaller.appspotmail.com Fixes: 493d9e0d6083 ("bpf, x86: add support for indirect jumps") Signed-off-by: Deepanshu Kartikey Acked-by: Anton Protopopov Link: https://lore.kernel.org/r/20260107021037.289644-1-kartikey406@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f0ca69f888fa..3135643d5695 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9609,6 +9609,11 @@ static int check_reg_const_str(struct bpf_verifier_env *env, if (reg->type != PTR_TO_MAP_VALUE) return -EINVAL; + if (map->map_type == BPF_MAP_TYPE_INSN_ARRAY) { + verbose(env, "R%d points to insn_array map which cannot be used as const string\n", regno); + return -EACCES; + } + if (!bpf_map_is_rdonly(map)) { verbose(env, "R%d does not point to a readonly map'\n", regno); return -EACCES;