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Message-ID: <20180105205711.1658397-1-ast@fb.com>
Date: Fri, 5 Jan 2018 12:57:11 -0800
From: Alexei Starovoitov <ast@...com>
To: "David S . Miller" <davem@...emloft.net>
CC: Daniel Borkmann <daniel@...earbox.net>, <netdev@...r.kernel.org>
Subject: [PATCH bpf-next] bpf: fix verifier GPF in kmalloc failure path
syzbot reported the following panic in the verifier triggered
by kmalloc error injection:
kasan: GPF could be caused by NULL-ptr deref or user memory access
RIP: 0010:copy_func_state kernel/bpf/verifier.c:403 [inline]
RIP: 0010:copy_verifier_state+0x364/0x590 kernel/bpf/verifier.c:431
Call Trace:
pop_stack+0x8c/0x270 kernel/bpf/verifier.c:449
push_stack kernel/bpf/verifier.c:491 [inline]
check_cond_jmp_op kernel/bpf/verifier.c:3598 [inline]
do_check+0x4b60/0xa050 kernel/bpf/verifier.c:4731
bpf_check+0x3296/0x58c0 kernel/bpf/verifier.c:5489
bpf_prog_load+0xa2a/0x1b00 kernel/bpf/syscall.c:1198
SYSC_bpf kernel/bpf/syscall.c:1807 [inline]
SyS_bpf+0x1044/0x4420 kernel/bpf/syscall.c:1769
when copy_verifier_state() aborts in the middle due to kmalloc failure
some of the frames could have been partially copied while
current free_verifier_state() loop
for (i = 0; i <= state->curframe; i++)
assumed that all frames are non-null.
Simply fix it by adding 'if (!state)' to free_func_state().
Also avoid stressing copy frame logic more if kzalloc fails
in push_stack() free env->cur_state right away.
Reported-by: syzbot+32ac5a3e473f2e01cfc7@...kaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
kernel/bpf/verifier.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a2b211262c25..d921ab387b0b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -375,6 +375,8 @@ static int realloc_func_state(struct bpf_func_state *state, int size,
static void free_func_state(struct bpf_func_state *state)
{
+ if (!state)
+ return;
kfree(state->stack);
kfree(state);
}
@@ -487,6 +489,8 @@ static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
}
return &elem->st;
err:
+ free_verifier_state(env->cur_state, true);
+ env->cur_state = NULL;
/* pop all elements and return */
while (!pop_stack(env, NULL, NULL));
return NULL;
--
2.9.5
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