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 --- lib/crypto/chacha20poly1305.c | 361 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 361 insertions(+) create mode 100644 lib/crypto/chacha20poly1305.c (limited to 'lib/crypto/chacha20poly1305.c') diff --git a/lib/crypto/chacha20poly1305.c b/lib/crypto/chacha20poly1305.c new file mode 100644 index 000000000..ea42a28f4 --- /dev/null +++ b/lib/crypto/chacha20poly1305.c @@ -0,0 +1,361 @@ +// SPDX-License-Identifier: GPL-2.0 OR MIT +/* + * Copyright (C) 2015-2019 Jason A. Donenfeld . All Rights Reserved. + * + * This is an implementation of the ChaCha20Poly1305 AEAD construction. + * + * Information: https://tools.ietf.org/html/rfc8439 + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static void chacha_load_key(u32 *k, const u8 *in) +{ + k[0] = get_unaligned_le32(in); + k[1] = get_unaligned_le32(in + 4); + k[2] = get_unaligned_le32(in + 8); + k[3] = get_unaligned_le32(in + 12); + k[4] = get_unaligned_le32(in + 16); + k[5] = get_unaligned_le32(in + 20); + k[6] = get_unaligned_le32(in + 24); + k[7] = get_unaligned_le32(in + 28); +} + +static void xchacha_init(struct chacha_state *chacha_state, + const u8 *key, const u8 *nonce) +{ + u32 k[CHACHA_KEY_WORDS]; + u8 iv[CHACHA_IV_SIZE]; + + memset(iv, 0, 8); + memcpy(iv + 8, nonce + 16, 8); + + chacha_load_key(k, key); + + /* Compute the subkey given the original key and first 128 nonce bits */ + chacha_init(chacha_state, k, nonce); + hchacha_block(chacha_state, k, 20); + + chacha_init(chacha_state, k, iv); + + memzero_explicit(k, sizeof(k)); + memzero_explicit(iv, sizeof(iv)); +} + +static void +__chacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + struct chacha_state *chacha_state) +{ + const u8 *pad0 = page_address(ZERO_PAGE(0)); + struct poly1305_desc_ctx poly1305_state; + union { + u8 block0[POLY1305_KEY_SIZE]; + __le64 lens[2]; + } b; + + chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0)); + poly1305_init(&poly1305_state, b.block0); + + poly1305_update(&poly1305_state, ad, ad_len); + if (ad_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf)); + + chacha20_crypt(chacha_state, dst, src, src_len); + + poly1305_update(&poly1305_state, dst, src_len); + if (src_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf)); + + b.lens[0] = cpu_to_le64(ad_len); + b.lens[1] = cpu_to_le64(src_len); + poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens)); + + poly1305_final(&poly1305_state, dst + src_len); + + chacha_zeroize_state(chacha_state); + memzero_explicit(&b, sizeof(b)); +} + +void chacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + const u64 nonce, + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + struct chacha_state chacha_state; + u32 k[CHACHA_KEY_WORDS]; + __le64 iv[2]; + + chacha_load_key(k, key); + + iv[0] = 0; + iv[1] = cpu_to_le64(nonce); + + chacha_init(&chacha_state, k, (u8 *)iv); + __chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, + &chacha_state); + + memzero_explicit(iv, sizeof(iv)); + memzero_explicit(k, sizeof(k)); +} +EXPORT_SYMBOL(chacha20poly1305_encrypt); + +void xchacha20poly1305_encrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + const u8 nonce[at_least XCHACHA20POLY1305_NONCE_SIZE], + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + struct chacha_state chacha_state; + + xchacha_init(&chacha_state, key, nonce); + __chacha20poly1305_encrypt(dst, src, src_len, ad, ad_len, + &chacha_state); +} +EXPORT_SYMBOL(xchacha20poly1305_encrypt); + +static bool +__chacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + struct chacha_state *chacha_state) +{ + const u8 *pad0 = page_address(ZERO_PAGE(0)); + struct poly1305_desc_ctx poly1305_state; + size_t dst_len; + int ret; + union { + u8 block0[POLY1305_KEY_SIZE]; + u8 mac[POLY1305_DIGEST_SIZE]; + __le64 lens[2]; + } b; + + if (unlikely(src_len < POLY1305_DIGEST_SIZE)) + return false; + + chacha20_crypt(chacha_state, b.block0, pad0, sizeof(b.block0)); + poly1305_init(&poly1305_state, b.block0); + + poly1305_update(&poly1305_state, ad, ad_len); + if (ad_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf)); + + dst_len = src_len - POLY1305_DIGEST_SIZE; + poly1305_update(&poly1305_state, src, dst_len); + if (dst_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (dst_len & 0xf)); + + b.lens[0] = cpu_to_le64(ad_len); + b.lens[1] = cpu_to_le64(dst_len); + poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens)); + + poly1305_final(&poly1305_state, b.mac); + + ret = crypto_memneq(b.mac, src + dst_len, POLY1305_DIGEST_SIZE); + if (likely(!ret)) + chacha20_crypt(chacha_state, dst, src, dst_len); + + memzero_explicit(&b, sizeof(b)); + + return !ret; +} + +bool chacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + const u64 nonce, + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + struct chacha_state chacha_state; + u32 k[CHACHA_KEY_WORDS]; + __le64 iv[2]; + bool ret; + + chacha_load_key(k, key); + + iv[0] = 0; + iv[1] = cpu_to_le64(nonce); + + chacha_init(&chacha_state, k, (u8 *)iv); + ret = __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len, + &chacha_state); + + chacha_zeroize_state(&chacha_state); + memzero_explicit(iv, sizeof(iv)); + memzero_explicit(k, sizeof(k)); + return ret; +} +EXPORT_SYMBOL(chacha20poly1305_decrypt); + +bool xchacha20poly1305_decrypt(u8 *dst, const u8 *src, const size_t src_len, + const u8 *ad, const size_t ad_len, + const u8 nonce[at_least XCHACHA20POLY1305_NONCE_SIZE], + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + struct chacha_state chacha_state; + + xchacha_init(&chacha_state, key, nonce); + return __chacha20poly1305_decrypt(dst, src, src_len, ad, ad_len, + &chacha_state); +} +EXPORT_SYMBOL(xchacha20poly1305_decrypt); + +static +bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src, + const size_t src_len, + const u8 *ad, const size_t ad_len, + const u64 nonce, + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE], + int encrypt) +{ + const u8 *pad0 = page_address(ZERO_PAGE(0)); + struct poly1305_desc_ctx poly1305_state; + struct chacha_state chacha_state; + struct sg_mapping_iter miter; + size_t partial = 0; + unsigned int flags; + bool ret = true; + int sl; + union { + struct { + u32 k[CHACHA_KEY_WORDS]; + __le64 iv[2]; + }; + u8 block0[POLY1305_KEY_SIZE]; + u8 chacha_stream[CHACHA_BLOCK_SIZE]; + struct { + u8 mac[2][POLY1305_DIGEST_SIZE]; + }; + __le64 lens[2]; + } b __aligned(16); + + if (WARN_ON(src_len > INT_MAX)) + return false; + + chacha_load_key(b.k, key); + + b.iv[0] = 0; + b.iv[1] = cpu_to_le64(nonce); + + chacha_init(&chacha_state, b.k, (u8 *)b.iv); + chacha20_crypt(&chacha_state, b.block0, pad0, sizeof(b.block0)); + poly1305_init(&poly1305_state, b.block0); + + if (unlikely(ad_len)) { + poly1305_update(&poly1305_state, ad, ad_len); + if (ad_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (ad_len & 0xf)); + } + + flags = SG_MITER_TO_SG | SG_MITER_ATOMIC; + + sg_miter_start(&miter, src, sg_nents(src), flags); + + for (sl = src_len; sl > 0 && sg_miter_next(&miter); sl -= miter.length) { + u8 *addr = miter.addr; + size_t length = min_t(size_t, sl, miter.length); + + if (!encrypt) + poly1305_update(&poly1305_state, addr, length); + + if (unlikely(partial)) { + size_t l = min(length, CHACHA_BLOCK_SIZE - partial); + + crypto_xor(addr, b.chacha_stream + partial, l); + partial = (partial + l) & (CHACHA_BLOCK_SIZE - 1); + + addr += l; + length -= l; + } + + if (likely(length >= CHACHA_BLOCK_SIZE || length == sl)) { + size_t l = length; + + if (unlikely(length < sl)) + l &= ~(CHACHA_BLOCK_SIZE - 1); + chacha20_crypt(&chacha_state, addr, addr, l); + addr += l; + length -= l; + } + + if (unlikely(length > 0)) { + chacha20_crypt(&chacha_state, b.chacha_stream, pad0, + CHACHA_BLOCK_SIZE); + crypto_xor(addr, b.chacha_stream, length); + partial = length; + } + + if (encrypt) + poly1305_update(&poly1305_state, miter.addr, + min_t(size_t, sl, miter.length)); + } + + if (src_len & 0xf) + poly1305_update(&poly1305_state, pad0, 0x10 - (src_len & 0xf)); + + b.lens[0] = cpu_to_le64(ad_len); + b.lens[1] = cpu_to_le64(src_len); + poly1305_update(&poly1305_state, (u8 *)b.lens, sizeof(b.lens)); + + if (likely(sl <= -POLY1305_DIGEST_SIZE)) { + if (encrypt) { + poly1305_final(&poly1305_state, + miter.addr + miter.length + sl); + ret = true; + } else { + poly1305_final(&poly1305_state, b.mac[0]); + ret = !crypto_memneq(b.mac[0], + miter.addr + miter.length + sl, + POLY1305_DIGEST_SIZE); + } + } + + sg_miter_stop(&miter); + + if (unlikely(sl > -POLY1305_DIGEST_SIZE)) { + poly1305_final(&poly1305_state, b.mac[1]); + sg_copy_buffer(src, sg_nents(src), b.mac[encrypt], + sizeof(b.mac[1]), src_len, !encrypt); + ret = encrypt || + !crypto_memneq(b.mac[0], b.mac[1], POLY1305_DIGEST_SIZE); + } + + chacha_zeroize_state(&chacha_state); + memzero_explicit(&b, sizeof(b)); + + return ret; +} + +bool chacha20poly1305_encrypt_sg_inplace(struct scatterlist *src, size_t src_len, + const u8 *ad, const size_t ad_len, + const u64 nonce, + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + return chacha20poly1305_crypt_sg_inplace(src, src_len, ad, ad_len, + nonce, key, 1); +} +EXPORT_SYMBOL(chacha20poly1305_encrypt_sg_inplace); + +bool chacha20poly1305_decrypt_sg_inplace(struct scatterlist *src, size_t src_len, + const u8 *ad, const size_t ad_len, + const u64 nonce, + const u8 key[at_least CHACHA20POLY1305_KEY_SIZE]) +{ + if (unlikely(src_len < POLY1305_DIGEST_SIZE)) + return false; + + return chacha20poly1305_crypt_sg_inplace(src, + src_len - POLY1305_DIGEST_SIZE, + ad, ad_len, nonce, key, 0); +} +EXPORT_SYMBOL(chacha20poly1305_decrypt_sg_inplace); + +MODULE_LICENSE("GPL v2"); +MODULE_DESCRIPTION("ChaCha20Poly1305 AEAD construction"); +MODULE_AUTHOR("Jason A. Donenfeld "); -- cgit v1.3.1