This is a note to let you know that I've just added the patch titled
bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb()
to the 4.14-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-test_run-fix-alignment-problem-in-bpf_prog_test_run_skb.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d3fd203f36d46aa29600a72d57a1b61af80e4a25 Mon Sep 17 00:00:00 2001
From: Baisong Zhong <zhongbaisong@xxxxxxxxxx>
Date: Wed, 2 Nov 2022 16:16:20 +0800
Subject: bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb()
From: Baisong Zhong <zhongbaisong@xxxxxxxxxx>
commit d3fd203f36d46aa29600a72d57a1b61af80e4a25 upstream.
We got a syzkaller problem because of aarch64 alignment fault
if KFENCE enabled. When the size from user bpf program is an odd
number, like 399, 407, etc, it will cause the struct skb_shared_info's
unaligned access. As seen below:
BUG: KFENCE: use-after-free read in __skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032
Use-after-free read at 0xffff6254fffac077 (in kfence-#213):
__lse_atomic_add arch/arm64/include/asm/atomic_lse.h:26 [inline]
arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
arch_atomic_inc include/linux/atomic-arch-fallback.h:270 [inline]
atomic_inc include/asm-generic/atomic-instrumented.h:241 [inline]
__skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032
skb_clone+0xf4/0x214 net/core/skbuff.c:1481
____bpf_clone_redirect net/core/filter.c:2433 [inline]
bpf_clone_redirect+0x78/0x1c0 net/core/filter.c:2420
bpf_prog_d3839dd9068ceb51+0x80/0x330
bpf_dispatcher_nop_func include/linux/bpf.h:728 [inline]
bpf_test_run+0x3c0/0x6c0 net/bpf/test_run.c:53
bpf_prog_test_run_skb+0x638/0xa7c net/bpf/test_run.c:594
bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline]
__do_sys_bpf kernel/bpf/syscall.c:4441 [inline]
__se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381
kfence-#213: 0xffff6254fffac000-0xffff6254fffac196, size=407, cache=kmalloc-512
allocated by task 15074 on cpu 0 at 1342.585390s:
kmalloc include/linux/slab.h:568 [inline]
kzalloc include/linux/slab.h:675 [inline]
bpf_test_init.isra.0+0xac/0x290 net/bpf/test_run.c:191
bpf_prog_test_run_skb+0x11c/0xa7c net/bpf/test_run.c:512
bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline]
__do_sys_bpf kernel/bpf/syscall.c:4441 [inline]
__se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381
__arm64_sys_bpf+0x50/0x60 kernel/bpf/syscall.c:4381
To fix the problem, we adjust @size so that (@size + @hearoom) is a
multiple of SMP_CACHE_BYTES. So we make sure the struct skb_shared_info
is aligned to a cache line.
Fixes: 1cf1cae963c2 ("bpf: introduce BPF_PROG_TEST_RUN command")
Signed-off-by: Baisong Zhong <zhongbaisong@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20221102081620.1465154-1-zhongbaisong@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/bpf/test_run.c | 1 +
1 file changed, 1 insertion(+)
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -78,6 +78,7 @@ static void *bpf_test_init(const union b
if (size < ETH_HLEN || size > PAGE_SIZE - headroom - tailroom)
return ERR_PTR(-EINVAL);
+ size = SKB_DATA_ALIGN(size);
data = kzalloc(size + headroom + tailroom, GFP_USER);
if (!data)
return ERR_PTR(-ENOMEM);
Patches currently in stable-queue which might be from zhongbaisong@xxxxxxxxxx are
queue-4.14/bpf-test_run-fix-alignment-problem-in-bpf_prog_test_run_skb.patch
