This is a note to let you know that I've just added the patch titled
bpf: Fix crash due to out of bounds access into reg2btf_ids.
to the 5.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-fix-crash-due-to-out-of-bounds-access-into-reg2b.patch
and it can be found in the queue-5.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ebb84ee5390911770b34d58e634ada2884436c92
Author: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Date: Thu Feb 17 01:49:43 2022 +0530
bpf: Fix crash due to out of bounds access into reg2btf_ids.
[ Upstream commit 45ce4b4f9009102cd9f581196d480a59208690c1 ]
When commit e6ac2450d6de ("bpf: Support bpf program calling kernel function") added
kfunc support, it defined reg2btf_ids as a cheap way to translate the verifier
reg type to the appropriate btf_vmlinux BTF ID, however
commit c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL")
moved the __BPF_REG_TYPE_MAX from the last member of bpf_reg_type enum to after
the base register types, and defined other variants using type flag
composition. However, now, the direct usage of reg->type to index into
reg2btf_ids may no longer fall into __BPF_REG_TYPE_MAX range, and hence lead to
out of bounds access and kernel crash on dereference of bad pointer.
Fixes: c25b2ae13603 ("bpf: Replace PTR_TO_XXX_OR_NULL with PTR_TO_XXX | PTR_MAYBE_NULL")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20220216201943.624869-1-memxor@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 1621f9d45fbda..c9da250fee38c 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5676,7 +5676,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
}
if (check_ctx_reg(env, reg, regno))
return -EINVAL;
- } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) {
+ } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
+ (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
const struct btf_type *reg_ref_t;
const struct btf *reg_btf;
const char *reg_ref_tname;
@@ -5694,7 +5695,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
reg_ref_id = reg->btf_id;
} else {
reg_btf = btf_vmlinux;
- reg_ref_id = *reg2btf_ids[reg->type];
+ reg_ref_id = *reg2btf_ids[base_type(reg->type)];
}
reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
