x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 307 insertions, 0 deletions

diff --git a/net/mac80211/wep.c b/net/mac80211/wep.c
new file mode 100644
index 000000000..93b866807
--- /dev/null
+++ b/net/mac80211/wep.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Software WEP encryption implementation
+ * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
+ * Copyright 2003, Instant802 Networks, Inc.
+ * Copyright (C) 2023 Intel Corporation
+ */
+
+#include <linux/netdevice.h>
+#include <linux/types.h>
+#include <linux/random.h>
+#include <linux/compiler.h>
+#include <linux/crc32.h>
+#include <linux/crypto.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/scatterlist.h>
+#include <linux/slab.h>
+#include <linux/unaligned.h>
+
+#include <net/mac80211.h>
+#include "ieee80211_i.h"
+#include "wep.h"
+
+
+void ieee80211_wep_init(struct ieee80211_local *local)
+{
+	/* start WEP IV from a random value */
+	get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN);
+}
+
+static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
+{
+	/*
+	 * Fluhrer, Mantin, and Shamir have reported weaknesses in the
+	 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
+	 * 0xff, N) can be used to speedup attacks, so avoid using them.
+	 */
+	if ((iv & 0xff00) == 0xff00) {
+		u8 B = (iv >> 16) & 0xff;
+		if (B >= 3 && B < 3 + keylen)
+			return true;
+	}
+	return false;
+}
+
+
+static void ieee80211_wep_get_iv(struct ieee80211_local *local,
+				 int keylen, int keyidx, u8 *iv)
+{
+	local->wep_iv++;
+	if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
+		local->wep_iv += 0x0100;
+
+	if (!iv)
+		return;
+
+	*iv++ = (local->wep_iv >> 16) & 0xff;
+	*iv++ = (local->wep_iv >> 8) & 0xff;
+	*iv++ = local->wep_iv & 0xff;
+	*iv++ = keyidx << 6;
+}
+
+
+static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
+				struct sk_buff *skb,
+				int keylen, int keyidx)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	unsigned int hdrlen;
+	u8 *newhdr;
+
+	hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
+
+	if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
+		return NULL;
+
+	hdrlen = ieee80211_hdrlen(hdr->frame_control);
+	newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
+	memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
+
+	/* the HW only needs room for the IV, but not the actual IV */
+	if (info->control.hw_key &&
+	    (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
+		return newhdr + hdrlen;
+
+	ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
+	return newhdr + hdrlen;
+}
+
+
+static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
+				    struct sk_buff *skb,
+				    struct ieee80211_key *key)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	unsigned int hdrlen;
+
+	hdrlen = ieee80211_hdrlen(hdr->frame_control);
+	memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
+	skb_pull(skb, IEEE80211_WEP_IV_LEN);
+}
+
+
+/* Perform WEP encryption using given key. data buffer must have tailroom
+ * for 4-byte ICV. data_len must not include this ICV. Note: this function
+ * does _not_ add IV. data = RC4(data | CRC32(data)) */
+int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
+			       size_t klen, u8 *data, size_t data_len)
+{
+	__le32 icv;
+
+	icv = cpu_to_le32(~crc32_le(~0, data, data_len));
+	put_unaligned(icv, (__le32 *)(data + data_len));
+
+	arc4_setkey(ctx, rc4key, klen);
+	arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
+	memzero_explicit(ctx, sizeof(*ctx));
+
+	return 0;
+}
+
+
+/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
+ * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
+ * buffer will be added. Both IV and ICV will be transmitted, so the
+ * payload length increases with 8 bytes.
+ *
+ * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
+ */
+int ieee80211_wep_encrypt(struct ieee80211_local *local,
+			  struct sk_buff *skb,
+			  const u8 *key, int keylen, int keyidx)
+{
+	u8 *iv;
+	size_t len;
+	u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
+
+	if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
+		return -1;
+
+	iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
+	if (!iv)
+		return -1;
+
+	len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
+
+	/* Prepend 24-bit IV to RC4 key */
+	memcpy(rc4key, iv, 3);
+
+	/* Copy rest of the WEP key (the secret part) */
+	memcpy(rc4key + 3, key, keylen);
+
+	/* Add room for ICV */
+	skb_put(skb, IEEE80211_WEP_ICV_LEN);
+
+	return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
+					  iv + IEEE80211_WEP_IV_LEN, len);
+}
+
+
+/* Perform WEP decryption using given key. data buffer includes encrypted
+ * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
+ * Return 0 on success and -1 on ICV mismatch. */
+int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
+			       size_t klen, u8 *data, size_t data_len)
+{
+	__le32 crc;
+
+	arc4_setkey(ctx, rc4key, klen);
+	arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
+	memzero_explicit(ctx, sizeof(*ctx));
+
+	crc = cpu_to_le32(~crc32_le(~0, data, data_len));
+	if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
+		/* ICV mismatch */
+		return -1;
+
+	return 0;
+}
+
+
+/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
+ * the frame: IV (4 bytes), encrypted payload (including SNAP header),
+ * ICV (4 bytes). skb->len includes both IV and ICV.
+ *
+ * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
+ * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
+ * is moved to the beginning of the skb and skb length will be reduced.
+ */
+static int ieee80211_wep_decrypt(struct ieee80211_local *local,
+				 struct sk_buff *skb,
+				 struct ieee80211_key *key)
+{
+	u32 klen;
+	u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
+	u8 keyidx;
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	unsigned int hdrlen;
+	size_t len;
+	int ret = 0;
+
+	if (!ieee80211_has_protected(hdr->frame_control))
+		return -1;
+
+	hdrlen = ieee80211_hdrlen(hdr->frame_control);
+	if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
+		return -1;
+
+	len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
+
+	keyidx = skb->data[hdrlen + 3] >> 6;
+
+	if (!key || keyidx != key->conf.keyidx)
+		return -1;
+
+	klen = 3 + key->conf.keylen;
+
+	/* Prepend 24-bit IV to RC4 key */
+	memcpy(rc4key, skb->data + hdrlen, 3);
+
+	/* Copy rest of the WEP key (the secret part) */
+	memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
+
+	if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
+				       skb->data + hdrlen +
+				       IEEE80211_WEP_IV_LEN, len))
+		ret = -1;
+
+	/* Trim ICV */
+	skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
+
+	/* Remove IV */
+	memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
+	skb_pull(skb, IEEE80211_WEP_IV_LEN);
+
+	return ret;
+}
+
+ieee80211_rx_result
+ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
+{
+	struct sk_buff *skb = rx->skb;
+	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
+	__le16 fc = hdr->frame_control;
+
+	if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
+		return RX_CONTINUE;
+
+	if (!(status->flag & RX_FLAG_DECRYPTED)) {
+		if (skb_linearize(rx->skb))
+			return RX_DROP_U_OOM;
+		if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
+			return RX_DROP_U_WEP_DEC_FAIL;
+	} else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
+		if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
+					    IEEE80211_WEP_IV_LEN))
+			return RX_DROP_U_NO_IV;
+		ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
+		/* remove ICV */
+		if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
+		    pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
+			return RX_DROP_U_NO_ICV;
+	}
+
+	return RX_CONTINUE;
+}
+
+static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_key_conf *hw_key = info->control.hw_key;
+
+	if (!hw_key) {
+		if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
+					  tx->key->conf.keylen,
+					  tx->key->conf.keyidx))
+			return -1;
+	} else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
+		   (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
+		if (!ieee80211_wep_add_iv(tx->local, skb,
+					  tx->key->conf.keylen,
+					  tx->key->conf.keyidx))
+			return -1;
+	}
+
+	return 0;
+}
+
+ieee80211_tx_result
+ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
+{
+	struct sk_buff *skb;
+
+	ieee80211_tx_set_protected(tx);
+
+	skb_queue_walk(&tx->skbs, skb) {
+		if (wep_encrypt_skb(tx, skb) < 0) {
+			I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
+			return TX_DROP;
+		}
+	}
+
+	return TX_CONTINUE;
+}