Patch "bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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 5.15-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_.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3b74cee070f7417990fd0049363ddb33926d016a
Author: Baisong Zhong <zhongbaisong@xxxxxxxxxx>
Date:   Wed Nov 2 16:16:20 2022 +0800

    bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb()
    
    [ Upstream commit d3fd203f36d46aa29600a72d57a1b61af80e4a25 ]
    
    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: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index a9fb16b9c735..7583ee98c35b 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -259,6 +259,7 @@ static void *bpf_test_init(const union bpf_attr *kattr, u32 size,
 	if (user_size > size)
 		return ERR_PTR(-EMSGSIZE);
 
+	size = SKB_DATA_ALIGN(size);
 	data = kzalloc(size + headroom + tailroom, GFP_USER);
 	if (!data)
 		return ERR_PTR(-ENOMEM);