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 --- fs/ext4/hash-test.c | 567 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 567 insertions(+) create mode 100644 fs/ext4/hash-test.c (limited to 'fs/ext4/hash-test.c') diff --git a/fs/ext4/hash-test.c b/fs/ext4/hash-test.c new file mode 100644 index 000000000..49b0d874c --- /dev/null +++ b/fs/ext4/hash-test.c @@ -0,0 +1,567 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KUnit tests for ext4 directory hash computation. + */ + +#include +#include +#include +#include +#include +#include +#include "ext4.h" + +static void ext4_hash_init_fake_dir(struct inode *dir, struct super_block *sb) +{ + memset(sb, 0, sizeof(*sb)); + memset(dir, 0, sizeof(*dir)); + dir->i_sb = sb; + strscpy(sb->s_id, "kunit-ext4", sizeof(sb->s_id)); +} + +static void ext4_hash_init_fake_dir_with_sbi(struct inode *dir, + struct super_block *sb, + struct ext4_sb_info *sbi) +{ + ext4_hash_init_fake_dir(dir, sb); + memset(sbi, 0, sizeof(*sbi)); + sb->s_fs_info = sbi; + sbi->s_sb = sb; +} + +#ifdef CONFIG_FS_ENCRYPTION +static const struct fscrypt_operations ext4_hash_test_cryptops = { + .inode_info_offs = + (int)offsetof(struct ext4_inode_info, i_crypt_info) - + (int)offsetof(struct ext4_inode_info, vfs_inode), +}; +#endif + +static void ext4_hash_init_fake_ext4_dir(struct ext4_inode_info *ei, + struct super_block *sb, + struct ext4_sb_info *sbi) +{ + struct inode *dir = &ei->vfs_inode; + + memset(sb, 0, sizeof(*sb)); + memset(ei, 0, sizeof(*ei)); + memset(sbi, 0, sizeof(*sbi)); + + strscpy(sb->s_id, "kunit-ext4", sizeof(sb->s_id)); + sb->s_fs_info = sbi; + sbi->s_sb = sb; + + dir->i_sb = sb; + dir->i_mode = S_IFDIR; + +#ifdef CONFIG_FS_ENCRYPTION + fscrypt_set_ops(sb, &ext4_hash_test_cryptops); +#endif +} + +struct ext4_dirhash_test_case { + const char *name; + u32 hash_version; + const char *input; + int len; + u32 seed[4]; + bool use_seed; + u32 expected_hash; + u32 expected_minor_hash; +}; + +static const struct ext4_dirhash_test_case ext4_dirhash_test_cases[] = { + { + .name = "legacy_abc", + .hash_version = DX_HASH_LEGACY, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0x75afd992, + .expected_minor_hash = 0x00000000, + }, + { + .name = "legacy_unsigned_abc", + .hash_version = DX_HASH_LEGACY_UNSIGNED, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0x75afd992, + .expected_minor_hash = 0x00000000, + }, + { + .name = "half_md4_abc", + .hash_version = DX_HASH_HALF_MD4, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0xd196a868, + .expected_minor_hash = 0xc420eb28, + }, + { + .name = "half_md4_unsigned_abc", + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0xd196a868, + .expected_minor_hash = 0xc420eb28, + }, + { + .name = "tea_abc", + .hash_version = DX_HASH_TEA, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0xb1435ec4, + .expected_minor_hash = 0x3f7eaa0e, + }, + { + .name = "tea_unsigned_abc", + .hash_version = DX_HASH_TEA_UNSIGNED, + .input = "abc", + .len = 3, + .use_seed = false, + .expected_hash = 0xb1435ec4, + .expected_minor_hash = 0x3f7eaa0e, + }, + { + .name = "empty_half_md4", + .hash_version = DX_HASH_HALF_MD4, + .input = "", + .len = 0, + .use_seed = false, + .expected_hash = 0xefcdab88, + .expected_minor_hash = 0x98badcfe, + }, + { + .name = "half_md4_31bytes", + .hash_version = DX_HASH_HALF_MD4, + .input = "1234567890123456789012345678901", + .len = 31, + .use_seed = false, + .expected_hash = 0xc4db1f78, + .expected_minor_hash = 0xea23921b, + }, + { + .name = "half_md4_32bytes", + .hash_version = DX_HASH_HALF_MD4, + .input = "12345678901234567890123456789012", + .len = 32, + .use_seed = false, + .expected_hash = 0xfa6cc63e, + .expected_minor_hash = 0x2f77bd1c, + }, + { + .name = "half_md4_33bytes", + .hash_version = DX_HASH_HALF_MD4, + .input = "123456789012345678901234567890123", + .len = 33, + .use_seed = false, + .expected_hash = 0xdc0c2dec, + .expected_minor_hash = 0x5ca23365, + }, + { + .name = "half_md4_unsigned_31bytes", + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + .input = "1234567890123456789012345678901", + .len = 31, + .use_seed = false, + .expected_hash = 0xc4db1f78, + .expected_minor_hash = 0xea23921b, + }, + { + .name = "half_md4_unsigned_32bytes", + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + .input = "12345678901234567890123456789012", + .len = 32, + .use_seed = false, + .expected_hash = 0xfa6cc63e, + .expected_minor_hash = 0x2f77bd1c, + }, + { + .name = "half_md4_unsigned_33bytes", + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + .input = "123456789012345678901234567890123", + .len = 33, + .use_seed = false, + .expected_hash = 0xdc0c2dec, + .expected_minor_hash = 0x5ca23365, + }, + { + .name = "tea_15bytes", + .hash_version = DX_HASH_TEA, + .input = "123456789abcdef", + .len = 15, + .use_seed = false, + .expected_hash = 0xa562903a, + .expected_minor_hash = 0x6174a00f, + }, + { + .name = "tea_16bytes", + .hash_version = DX_HASH_TEA, + .input = "1234567890abcdef", + .len = 16, + .use_seed = false, + .expected_hash = 0x8449f258, + .expected_minor_hash = 0x49a16d46, + }, + { + .name = "tea_17bytes", + .hash_version = DX_HASH_TEA, + .input = "123456789abcdefgh", + .len = 17, + .use_seed = false, + .expected_hash = 0xf32ec10c, + .expected_minor_hash = 0x58ceae61, + }, + { + .name = "half_md4_seeded", + .hash_version = DX_HASH_HALF_MD4, + .input = "same-name", + .len = 9, + .seed = { 0x11111111, 0x22222222, 0x33333333, 0x44444444 }, + .use_seed = true, + .expected_hash = 0x8aebf604, + .expected_minor_hash = 0x66ce48fe, + }, + { + .name = "half_md4_non_ascii_signed", + .hash_version = DX_HASH_HALF_MD4, + .input = "\x80\x81\x82\x83\x84", + .len = 5, + .use_seed = false, + .expected_hash = 0x8bab0498, + .expected_minor_hash = 0xc326632d, + }, + { + .name = "half_md4_non_ascii_unsigned", + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + .input = "\x80\x81\x82\x83\x84", + .len = 5, + .use_seed = false, + .expected_hash = 0xbc48596e, + .expected_minor_hash = 0xde0fad41, + }, + { + .name = "tea_non_ascii_signed", + .hash_version = DX_HASH_TEA, + .input = "\x80\x81\x82\x83\x84", + .len = 5, + .use_seed = false, + .expected_hash = 0x21e3a154, + .expected_minor_hash = 0x90112c3d, + }, + { + .name = "tea_non_ascii_unsigned", + .hash_version = DX_HASH_TEA_UNSIGNED, + .input = "\x80\x81\x82\x83\x84", + .len = 5, + .use_seed = false, + .expected_hash = 0x9b648616, + .expected_minor_hash = 0x011dd507, + }, +}; + +static void test_ext4fs_dirhash_vectors(struct kunit *test) +{ + struct super_block *sb; + struct inode *dir; + int i; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + dir = kunit_kzalloc(test, sizeof(*dir), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, dir); + + ext4_hash_init_fake_dir(dir, sb); + + for (i = 0; i < ARRAY_SIZE(ext4_dirhash_test_cases); i++) { + const struct ext4_dirhash_test_case *tc = + &ext4_dirhash_test_cases[i]; + struct dx_hash_info hinfo; + int ret; + + memset(&hinfo, 0, sizeof(hinfo)); + hinfo.hash_version = tc->hash_version; + hinfo.seed = tc->use_seed ? (u32 *)tc->seed : NULL; + + ret = ext4fs_dirhash(dir, tc->input, tc->len, &hinfo); + + KUNIT_ASSERT_EQ_MSG(test, ret, 0, "case=%s", tc->name); + KUNIT_EXPECT_EQ_MSG(test, hinfo.hash, tc->expected_hash, + "case=%s", tc->name); + KUNIT_EXPECT_EQ_MSG(test, hinfo.minor_hash, + tc->expected_minor_hash, + "case=%s", tc->name); + } +} + +static void test_ext4fs_dirhash_seed_changes_result(struct kunit *test) +{ + struct super_block *sb; + struct inode *dir; + u32 seed[4] = { 0x11111111, 0x22222222, 0x33333333, 0x44444444 }; + struct dx_hash_info plain = { + .hash_version = DX_HASH_HALF_MD4, + }; + struct dx_hash_info seeded = { + .hash_version = DX_HASH_HALF_MD4, + .seed = seed, + }; + int ret_plain, ret_seeded; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + dir = kunit_kzalloc(test, sizeof(*dir), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, dir); + + ext4_hash_init_fake_dir(dir, sb); + + ret_plain = ext4fs_dirhash(dir, "same-name", 9, &plain); + ret_seeded = ext4fs_dirhash(dir, "same-name", 9, &seeded); + + KUNIT_ASSERT_EQ(test, ret_plain, 0); + KUNIT_ASSERT_EQ(test, ret_seeded, 0); + + KUNIT_EXPECT_TRUE(test, + plain.hash != seeded.hash || + plain.minor_hash != seeded.minor_hash); +} + +static void test_ext4fs_dirhash_invalid_version_returns_einval(struct kunit *test) +{ + struct super_block *sb; + struct inode *dir; + struct ext4_sb_info *sbi; + struct dx_hash_info hinfo = { + .hash = 0xdeadbeef, + .minor_hash = 0xcafebabe, + .hash_version = DX_HASH_LAST + 1, + }; + int ret; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + dir = kunit_kzalloc(test, sizeof(*dir), GFP_KERNEL); + sbi = kunit_kzalloc(test, sizeof(*sbi), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, dir); + KUNIT_ASSERT_NOT_NULL(test, sbi); + + ext4_hash_init_fake_dir_with_sbi(dir, sb, sbi); + + ret = ext4fs_dirhash(dir, "abc", 3, &hinfo); + + KUNIT_EXPECT_EQ(test, ret, -EINVAL); + KUNIT_EXPECT_EQ(test, hinfo.hash, 0); + KUNIT_EXPECT_EQ(test, hinfo.minor_hash, 0); +} + +static void test_ext4fs_dirhash_siphash_without_key_returns_einval(struct kunit *test) +{ + struct super_block *sb; + struct ext4_inode_info *ei; + struct inode *dir; + struct ext4_sb_info *sbi; + struct dx_hash_info hinfo = { + .hash_version = DX_HASH_SIPHASH, + }; + int ret; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + ei = kunit_kzalloc(test, sizeof(*ei), GFP_KERNEL); + sbi = kunit_kzalloc(test, sizeof(*sbi), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, ei); + KUNIT_ASSERT_NOT_NULL(test, sbi); + + ext4_hash_init_fake_ext4_dir(ei, sb, sbi); + dir = &ei->vfs_inode; + + ret = ext4fs_dirhash(dir, "name", strlen("name"), &hinfo); + + KUNIT_EXPECT_EQ(test, ret, -EINVAL); +} + +static void test_ext4fs_dirhash_signed_unsigned_differ_on_nonascii(struct kunit *test) +{ + struct super_block *sb; + struct inode *dir; + static const char input[] = "\x80\xff\x81\xfe\101bc"; + struct dx_hash_info legacy_signed = { + .hash_version = DX_HASH_LEGACY, + }; + struct dx_hash_info legacy_unsigned = { + .hash_version = DX_HASH_LEGACY_UNSIGNED, + }; + struct dx_hash_info md4_signed = { + .hash_version = DX_HASH_HALF_MD4, + }; + struct dx_hash_info md4_unsigned = { + .hash_version = DX_HASH_HALF_MD4_UNSIGNED, + }; + struct dx_hash_info tea_signed = { + .hash_version = DX_HASH_TEA, + }; + struct dx_hash_info tea_unsigned = { + .hash_version = DX_HASH_TEA_UNSIGNED, + }; + int ret; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + dir = kunit_kzalloc(test, sizeof(*dir), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, dir); + + ext4_hash_init_fake_dir(dir, sb); + + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &legacy_signed); + KUNIT_ASSERT_EQ(test, ret, 0); + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &legacy_unsigned); + KUNIT_ASSERT_EQ(test, ret, 0); + KUNIT_EXPECT_NE(test, legacy_signed.hash, legacy_unsigned.hash); + + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &md4_signed); + KUNIT_ASSERT_EQ(test, ret, 0); + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &md4_unsigned); + KUNIT_ASSERT_EQ(test, ret, 0); + KUNIT_EXPECT_TRUE(test, + md4_signed.hash != md4_unsigned.hash || + md4_signed.minor_hash != md4_unsigned.minor_hash); + + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &tea_signed); + KUNIT_ASSERT_EQ(test, ret, 0); + ret = ext4fs_dirhash(dir, input, sizeof(input) - 1, &tea_unsigned); + KUNIT_ASSERT_EQ(test, ret, 0); + KUNIT_EXPECT_TRUE(test, + tea_signed.hash != tea_unsigned.hash || + tea_signed.minor_hash != tea_unsigned.minor_hash); +} + +#if IS_ENABLED(CONFIG_UNICODE) +KUNIT_DEFINE_ACTION_WRAPPER(utf8_unload_action, utf8_unload, + struct unicode_map *); +static void test_ext4fs_dirhash_casefolded_names_hash_consistently(struct kunit *test) +{ + struct super_block *sb; + struct ext4_inode_info *ei; + struct ext4_sb_info *sbi; + struct unicode_map *um; + struct dx_hash_info h1 = { + .hash_version = DX_HASH_HALF_MD4, + }; + struct dx_hash_info h2 = { + .hash_version = DX_HASH_HALF_MD4, + }; + int ret, ret1, ret2; + + sb = kunit_kzalloc(test, sizeof(*sb), GFP_KERNEL); + ei = kunit_kzalloc(test, sizeof(*ei), GFP_KERNEL); + sbi = kunit_kzalloc(test, sizeof(*sbi), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb); + KUNIT_ASSERT_NOT_NULL(test, ei); + KUNIT_ASSERT_NOT_NULL(test, sbi); + + um = utf8_load(UTF8_LATEST); + if (IS_ERR(um)) { + kunit_skip(test, "utf8_load(UTF8_LATEST) failed: %pe", + um); + return; + } + + ret = kunit_add_action_or_reset(test, utf8_unload_action, um); + KUNIT_ASSERT_EQ(test, ret, 0); + + ext4_hash_init_fake_ext4_dir(ei, sb, sbi); + sb->s_encoding = um; + ei->vfs_inode.i_flags |= S_CASEFOLD; + + KUNIT_ASSERT_TRUE(test, IS_CASEFOLDED(&ei->vfs_inode)); + + ret1 = ext4fs_dirhash(&ei->vfs_inode, "Alpha", 5, &h1); + ret2 = ext4fs_dirhash(&ei->vfs_inode, "aLPHa", 5, &h2); + + KUNIT_ASSERT_EQ(test, ret1, 0); + KUNIT_ASSERT_EQ(test, ret2, 0); + KUNIT_EXPECT_EQ(test, h1.hash, h2.hash); + KUNIT_EXPECT_EQ(test, h1.minor_hash, h2.minor_hash); +} + +static void test_ext4fs_dirhash_casefold_fallback(struct kunit *test) +{ + struct super_block *sb_cf, *sb_plain; + struct ext4_inode_info *ei; + struct ext4_sb_info *sbi; + struct inode *plain_dir; + struct unicode_map *um; + static const char invalid_utf8[] = "\xc3\x28"; + struct dx_hash_info folded_dir = { + .hash_version = DX_HASH_HALF_MD4, + }; + struct dx_hash_info plain = { + .hash_version = DX_HASH_HALF_MD4, + }; + int ret, ret_cf, ret_plain; + + sb_cf = kunit_kzalloc(test, sizeof(*sb_cf), GFP_KERNEL); + sb_plain = kunit_kzalloc(test, sizeof(*sb_plain), GFP_KERNEL); + ei = kunit_kzalloc(test, sizeof(*ei), GFP_KERNEL); + sbi = kunit_kzalloc(test, sizeof(*sbi), GFP_KERNEL); + plain_dir = kunit_kzalloc(test, sizeof(*plain_dir), GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, sb_cf); + KUNIT_ASSERT_NOT_NULL(test, sb_plain); + KUNIT_ASSERT_NOT_NULL(test, ei); + KUNIT_ASSERT_NOT_NULL(test, sbi); + KUNIT_ASSERT_NOT_NULL(test, plain_dir); + + um = utf8_load(UTF8_LATEST); + if (IS_ERR(um)) { + kunit_skip(test, "utf8_load(UTF8_LATEST) failed: %pe", + um); + return; + } + + ret = kunit_add_action_or_reset(test, utf8_unload_action, um); + KUNIT_ASSERT_EQ(test, ret, 0); + + ext4_hash_init_fake_ext4_dir(ei, sb_cf, sbi); + sb_cf->s_encoding = um; + ei->vfs_inode.i_flags |= S_CASEFOLD; + + KUNIT_ASSERT_TRUE(test, IS_CASEFOLDED(&ei->vfs_inode)); + + ext4_hash_init_fake_dir(plain_dir, sb_plain); + + ret_cf = ext4fs_dirhash(&ei->vfs_inode, invalid_utf8, + sizeof(invalid_utf8) - 1, &folded_dir); + ret_plain = ext4fs_dirhash(plain_dir, invalid_utf8, + sizeof(invalid_utf8) - 1, &plain); + + KUNIT_ASSERT_EQ(test, ret_cf, 0); + KUNIT_ASSERT_EQ(test, ret_plain, 0); + KUNIT_EXPECT_EQ(test, folded_dir.hash, plain.hash); + KUNIT_EXPECT_EQ(test, folded_dir.minor_hash, plain.minor_hash); +} +#endif + +static struct kunit_case ext4_hash_test_cases[] = { + KUNIT_CASE(test_ext4fs_dirhash_vectors), + KUNIT_CASE(test_ext4fs_dirhash_seed_changes_result), + KUNIT_CASE(test_ext4fs_dirhash_invalid_version_returns_einval), + KUNIT_CASE(test_ext4fs_dirhash_siphash_without_key_returns_einval), + KUNIT_CASE(test_ext4fs_dirhash_signed_unsigned_differ_on_nonascii), +#if IS_ENABLED(CONFIG_UNICODE) + KUNIT_CASE(test_ext4fs_dirhash_casefolded_names_hash_consistently), + KUNIT_CASE(test_ext4fs_dirhash_casefold_fallback), +#endif + {} +}; + +static struct kunit_suite ext4_hash_test_suite = { + .name = "ext4_hash", + .test_cases = ext4_hash_test_cases, +}; + +kunit_test_suites(&ext4_hash_test_suite); + +MODULE_LICENSE("GPL"); -- cgit v1.3.1