diff options
| author | Kuniyuki Iwashima <kuniyu@amazon.com> | 2025-01-31 19:01:42 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-27 04:30:19 -0800 |
| commit | f579afacd0a66971fc8481f30d2d377e230a8342 (patch) | |
| tree | d04a1d102e5f41fd061c0b274fd2467aea38881e /kernel | |
| parent | abd30e947f70e846f2b7fdf164c23a929696b181 (diff) | |
| download | linux-f579afacd0a66971fc8481f30d2d377e230a8342.tar.gz linux-f579afacd0a66971fc8481f30d2d377e230a8342.tar.bz2 linux-f579afacd0a66971fc8481f30d2d377e230a8342.zip | |
net: Add rx_skb of kfree_skb to raw_tp_null_args[].
[ Upstream commit 5da7e15fb5a12e78de974d8908f348e279922ce9 ]
Yan Zhai reported a BPF prog could trigger a null-ptr-deref [0]
in trace_kfree_skb if the prog does not check if rx_sk is NULL.
Commit c53795d48ee8 ("net: add rx_sk to trace_kfree_skb") added
rx_sk to trace_kfree_skb, but rx_sk is optional and could be NULL.
Let's add kfree_skb to raw_tp_null_args[] to let the BPF verifier
validate such a prog and prevent the issue.
Now we fail to load such a prog:
libbpf: prog 'drop': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0
; int BPF_PROG(drop, struct sk_buff *skb, void *location, @ kfree_skb_sk_null.bpf.c:21
0: (79) r3 = *(u64 *)(r1 +24)
func 'kfree_skb' arg3 has btf_id 5253 type STRUCT 'sock'
1: R1=ctx() R3_w=trusted_ptr_or_null_sock(id=1)
; bpf_printk("sk: %d, %d\n", sk, sk->__sk_common.skc_family); @ kfree_skb_sk_null.bpf.c:24
1: (69) r4 = *(u16 *)(r3 +16)
R3 invalid mem access 'trusted_ptr_or_null_'
processed 2 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
-- END PROG LOAD LOG --
Note this fix requires commit 838a10bd2ebf ("bpf: Augment raw_tp
arguments with PTR_MAYBE_NULL").
[0]:
BUG: kernel NULL pointer dereference, address: 0000000000000010
PF: supervisor read access in kernel mode
PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
PREEMPT SMP
RIP: 0010:bpf_prog_5e21a6db8fcff1aa_drop+0x10/0x2d
Call Trace:
<TASK>
? __die+0x1f/0x60
? page_fault_oops+0x148/0x420
? search_bpf_extables+0x5b/0x70
? fixup_exception+0x27/0x2c0
? exc_page_fault+0x75/0x170
? asm_exc_page_fault+0x22/0x30
? bpf_prog_5e21a6db8fcff1aa_drop+0x10/0x2d
bpf_trace_run4+0x68/0xd0
? unix_stream_connect+0x1f4/0x6f0
sk_skb_reason_drop+0x90/0x120
unix_stream_connect+0x1f4/0x6f0
__sys_connect+0x7f/0xb0
__x64_sys_connect+0x14/0x20
do_syscall_64+0x47/0xc30
entry_SYSCALL_64_after_hwframe+0x4b/0x53
Fixes: c53795d48ee8 ("net: add rx_sk to trace_kfree_skb")
Reported-by: Yan Zhai <yan@cloudflare.com>
Closes: https://lore.kernel.org/netdev/Z50zebTRzI962e6X@debian.debian/
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Tested-by: Yan Zhai <yan@cloudflare.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20250201030142.62703-1-kuniyu@amazon.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/btf.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index a44f4be592be..2c54c148a94f 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6483,6 +6483,8 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = { /* rxrpc */ { "rxrpc_recvdata", 0x1 }, { "rxrpc_resend", 0x10 }, + /* skb */ + {"kfree_skb", 0x1000}, /* sunrpc */ { "xs_stream_read_data", 0x1 }, /* ... from xprt_cong_event event class */ |