From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- include/crypto/internal/des.h | 127 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 127 insertions(+) create mode 100644 include/crypto/internal/des.h (limited to 'include/crypto/internal/des.h') diff --git a/include/crypto/internal/des.h b/include/crypto/internal/des.h new file mode 100644 index 000000000..723fe5bf1 --- /dev/null +++ b/include/crypto/internal/des.h @@ -0,0 +1,127 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * DES & Triple DES EDE key verification helpers + */ + +#ifndef __CRYPTO_INTERNAL_DES_H +#define __CRYPTO_INTERNAL_DES_H + +#include +#include +#include +#include +#include + +/** + * crypto_des_verify_key - Check whether a DES key is weak + * @tfm: the crypto algo + * @key: the key buffer + * + * Returns -EINVAL if the key is weak and the crypto TFM does not permit weak + * keys. Otherwise, 0 is returned. + * + * It is the job of the caller to ensure that the size of the key equals + * DES_KEY_SIZE. + */ +static inline int crypto_des_verify_key(struct crypto_tfm *tfm, const u8 *key) +{ + struct des_ctx tmp; + int err; + + err = des_expand_key(&tmp, key, DES_KEY_SIZE); + if (err == -ENOKEY) { + if (crypto_tfm_get_flags(tfm) & CRYPTO_TFM_REQ_FORBID_WEAK_KEYS) + err = -EINVAL; + else + err = 0; + } + memzero_explicit(&tmp, sizeof(tmp)); + return err; +} + +/* + * RFC2451: + * + * For DES-EDE3, there is no known need to reject weak or + * complementation keys. Any weakness is obviated by the use of + * multiple keys. + * + * However, if the first two or last two independent 64-bit keys are + * equal (k1 == k2 or k2 == k3), then the DES3 operation is simply the + * same as DES. Implementers MUST reject keys that exhibit this + * property. + * + */ +static inline int des3_ede_verify_key(const u8 *key, unsigned int key_len, + bool check_weak) +{ + int ret = fips_enabled ? -EINVAL : -ENOKEY; + u32 K[6]; + + memcpy(K, key, DES3_EDE_KEY_SIZE); + + if ((!((K[0] ^ K[2]) | (K[1] ^ K[3])) || + !((K[2] ^ K[4]) | (K[3] ^ K[5]))) && + (fips_enabled || check_weak)) + goto bad; + + if ((!((K[0] ^ K[4]) | (K[1] ^ K[5]))) && fips_enabled) + goto bad; + + ret = 0; +bad: + memzero_explicit(K, DES3_EDE_KEY_SIZE); + + return ret; +} + +/** + * crypto_des3_ede_verify_key - Check whether a DES3-EDE key is weak + * @tfm: the crypto algo + * @key: the key buffer + * + * Returns -EINVAL if the key is weak and the crypto TFM does not permit weak + * keys or when running in FIPS mode. Otherwise, 0 is returned. Note that some + * keys are rejected in FIPS mode even if weak keys are permitted by the TFM + * flags. + * + * It is the job of the caller to ensure that the size of the key equals + * DES3_EDE_KEY_SIZE. + */ +static inline int crypto_des3_ede_verify_key(struct crypto_tfm *tfm, + const u8 *key) +{ + return des3_ede_verify_key(key, DES3_EDE_KEY_SIZE, + crypto_tfm_get_flags(tfm) & + CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); +} + +static inline int verify_skcipher_des_key(struct crypto_skcipher *tfm, + const u8 *key) +{ + return crypto_des_verify_key(crypto_skcipher_tfm(tfm), key); +} + +static inline int verify_skcipher_des3_key(struct crypto_skcipher *tfm, + const u8 *key) +{ + return crypto_des3_ede_verify_key(crypto_skcipher_tfm(tfm), key); +} + +static inline int verify_aead_des_key(struct crypto_aead *tfm, const u8 *key, + int keylen) +{ + if (keylen != DES_KEY_SIZE) + return -EINVAL; + return crypto_des_verify_key(crypto_aead_tfm(tfm), key); +} + +static inline int verify_aead_des3_key(struct crypto_aead *tfm, const u8 *key, + int keylen) +{ + if (keylen != DES3_EDE_KEY_SIZE) + return -EINVAL; + return crypto_des3_ede_verify_key(crypto_aead_tfm(tfm), key); +} + +#endif /* __CRYPTO_INTERNAL_DES_H */ -- cgit v1.3.1