6.12-stable review patch. If anyone has any objections, please let me know.
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From: Shigeru Yoshida syoshida@redhat.com
[ Upstream commit 6b3d638ca897e099fa99bd6d02189d3176f80a47 ]
KMSAN reported a use-after-free issue in eth_skb_pkt_type()[1]. The cause of the issue was that eth_skb_pkt_type() accessed skb's data that didn't contain an Ethernet header. This occurs when bpf_prog_test_run_xdp() passes an invalid value as the user_data argument to bpf_test_init().
Fix this by returning an error when user_data is less than ETH_HLEN in bpf_test_init(). Additionally, remove the check for "if (user_size > size)" as it is unnecessary.
[1] BUG: KMSAN: use-after-free in eth_skb_pkt_type include/linux/etherdevice.h:627 [inline] BUG: KMSAN: use-after-free in eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165 eth_skb_pkt_type include/linux/etherdevice.h:627 [inline] eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165 __xdp_build_skb_from_frame+0x5a8/0xa50 net/core/xdp.c:635 xdp_recv_frames net/bpf/test_run.c:272 [inline] xdp_test_run_batch net/bpf/test_run.c:361 [inline] bpf_test_run_xdp_live+0x2954/0x3330 net/bpf/test_run.c:390 bpf_prog_test_run_xdp+0x148e/0x1b10 net/bpf/test_run.c:1318 bpf_prog_test_run+0x5b7/0xa30 kernel/bpf/syscall.c:4371 __sys_bpf+0x6a6/0xe20 kernel/bpf/syscall.c:5777 __do_sys_bpf kernel/bpf/syscall.c:5866 [inline] __se_sys_bpf kernel/bpf/syscall.c:5864 [inline] __x64_sys_bpf+0xa4/0xf0 kernel/bpf/syscall.c:5864 x64_sys_call+0x2ea0/0x3d90 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xd9/0x1d0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Uninit was created at: free_pages_prepare mm/page_alloc.c:1056 [inline] free_unref_page+0x156/0x1320 mm/page_alloc.c:2657 __free_pages+0xa3/0x1b0 mm/page_alloc.c:4838 bpf_ringbuf_free kernel/bpf/ringbuf.c:226 [inline] ringbuf_map_free+0xff/0x1e0 kernel/bpf/ringbuf.c:235 bpf_map_free kernel/bpf/syscall.c:838 [inline] bpf_map_free_deferred+0x17c/0x310 kernel/bpf/syscall.c:862 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa2b/0x1b60 kernel/workqueue.c:3310 worker_thread+0xedf/0x1550 kernel/workqueue.c:3391 kthread+0x535/0x6b0 kernel/kthread.c:389 ret_from_fork+0x6e/0x90 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
CPU: 1 UID: 0 PID: 17276 Comm: syz.1.16450 Not tainted 6.12.0-05490-g9bb88c659673 #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
Fixes: be3d72a2896c ("bpf: move user_size out of bpf_test_init") Reported-by: syzkaller syzkaller@googlegroups.com Suggested-by: Martin KaFai Lau martin.lau@linux.dev Signed-off-by: Shigeru Yoshida syoshida@redhat.com Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Acked-by: Stanislav Fomichev sdf@fomichev.me Acked-by: Daniel Borkmann daniel@iogearbox.net Link: https://patch.msgid.link/20250121150643.671650-1-syoshida@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/bpf/test_run.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 501ec4249fedc..8612023bec60d 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -660,12 +660,9 @@ static void *bpf_test_init(const union bpf_attr *kattr, u32 user_size, void __user *data_in = u64_to_user_ptr(kattr->test.data_in); void *data;
- if (size < ETH_HLEN || size > PAGE_SIZE - headroom - tailroom) + if (user_size < ETH_HLEN || user_size > PAGE_SIZE - headroom - tailroom) return ERR_PTR(-EINVAL);
- if (user_size > size) - return ERR_PTR(-EMSGSIZE); - size = SKB_DATA_ALIGN(size); data = kzalloc(size + headroom + tailroom, GFP_USER); if (!data)