Commit 9df5fad8 authored by Deepanshu Kartikey's avatar Deepanshu Kartikey Committed by Alexei Starovoitov
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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: default avatar <syzbot+2c29addf92581b410079@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=2c29addf92581b410079


Tested-by: default avatar <syzbot+2c29addf92581b410079@syzkaller.appspotmail.com>
Fixes: 493d9e0d ("bpf, x86: add support for indirect jumps")
Signed-off-by: default avatarDeepanshu Kartikey <kartikey406@gmail.com>
Acked-by: default avatarAnton Protopopov <a.s.protopopov@gmail.com>
Link: https://lore.kernel.org/r/20260107021037.289644-1-kartikey406@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ab86d0bf

kernel/bpf/verifier.c

+5 −0
Original line number Diff line number Diff line
@@ -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;