[PATCH 5.14 094/334] bpf: Fix potential memleak and UAF in the verifier.

Greg Kroah-Hartman
2021-09-13T14:31:08Z

From: He Fengqing <hefengqing@huawei.com>

[ Upstream commit 75f0fc7b48ad45a2e5736bcf8de26c8872fe8695 ]

In bpf_patch_insn_data(), we first use the bpf_patch_insn_single() to
insert new instructions, then use adjust_insn_aux_data() to adjust
insn_aux_data. If the old env->prog have no enough room for new inserted
instructions, we use bpf_prog_realloc to construct new_prog and free the
old env->prog.

There have two errors here. First, if adjust_insn_aux_data() return
ENOMEM, we should free the new_prog. Second, if adjust_insn_aux_data()
return ENOMEM, bpf_patch_insn_data() will return NULL, and env->prog has
been freed in bpf_prog_realloc, but we will use it in bpf_check().

So in this patch, we make the adjust_insn_aux_data() never fails. In
bpf_patch_insn_data(), we first pre-malloc memory for the new
insn_aux_data, then call bpf_patch_insn_single() to insert new
instructions, at last call adjust_insn_aux_data() to adjust
insn_aux_data.

Fixes: 8041902dae52 ("bpf: adjust insn_aux_data when patching insns")
Signed-off-by: He Fengqing <hefengqing@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210714101815.164322-1-hefengqing@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/verifier.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 49f07e2bf23b..10084c0600dd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11414,10 +11414,11 @@ static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
* insni[off, off + cnt). Adjust corresponding insn_aux_data by copying
* [0, off) and [off, end) to new locations, so the patched range stays zero
*/
-static int adjust_insn_aux_data(struct bpf_verifier_env *env,
- struct bpf_prog *new_prog, u32 off, u32 cnt)
+static void adjust_insn_aux_data(struct bpf_verifier_env *env,
+ struct bpf_insn_aux_data *new_data,
+ struct bpf_prog *new_prog, u32 off, u32 cnt)
{
- struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
+ struct bpf_insn_aux_data *old_data = env->insn_aux_data;
struct bpf_insn *insn = new_prog->insnsi;
u32 old_seen = old_data[off].seen;
u32 prog_len;
@@ -11430,12 +11431,9 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env,
old_data[off].zext_dst = insn_has_def32(env, insn + off + cnt - 1);

if (cnt == 1)
- return 0;
+ return;
prog_len = new_prog->len;
- new_data = vzalloc(array_size(prog_len,
- sizeof(struct bpf_insn_aux_data)));
- if (!new_data)
- return -ENOMEM;
+
memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
memcpy(new_data + off + cnt - 1, old_data + off,
sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
@@ -11446,7 +11444,6 @@ static int adjust_insn_aux_data(struct bpf_verifier_env *env,
}
env->insn_aux_data = new_data;
vfree(old_data);
- return 0;
}

static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len)
@@ -11481,6 +11478,14 @@ static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 of
const struct bpf_insn *patch, u32 len)
{
struct bpf_prog *new_prog;
+ struct bpf_insn_aux_data *new_data = NULL;
+
+ if (len > 1) {
+ new_data = vzalloc(array_size(env->prog->len + len - 1,
+ sizeof(struct bpf_insn_aux_data)));
+ if (!new_data)
+ return NULL;
+ }

new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
if (IS_ERR(new_prog)) {
@@ -11488,10 +11493,10 @@ static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 of
verbose(env,
"insn %d cannot be patched due to 16-bit range\n",
env->insn_aux_data[off].orig_idx);
+ vfree(new_data);
return NULL;
}
- if (adjust_insn_aux_data(env, new_prog, off, len))
- return NULL;
+ adjust_insn_aux_data(env, new_data, new_prog, off, len);
adjust_subprog_starts(env, off, len);
adjust_poke_descs(new_prog, off, len);
return new_prog;
--
2.30.2