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| author | Masami Hiramatsu <mhiramat@kernel.org> | 2021-03-25 13:08:31 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-03-25 13:37:21 +0300 |
| commit | 6dd3b8c9f58816a1354be39559f630cd1bd12159 (patch) | |
| tree | b56890da4523ca722bdc20aaf84a47532b658797 /arch/x86/kernel/kprobes | |
| parent | 6256e668b7af9d81472e03c6a171630c08f8858a (diff) | |
| download | linux-6dd3b8c9f58816a1354be39559f630cd1bd12159.tar.xz | |
x86/kprobes: Fix to check non boostable prefixes correctly
There are 2 bugs in the can_boost() function because of using
x86 insn decoder. Since the insn->opcode never has a prefix byte,
it can not find CS override prefix in it. And the insn->attr is
the attribute of the opcode, thus inat_is_address_size_prefix(
insn->attr) always returns false.
Fix those by checking each prefix bytes with for_each_insn_prefix
loop and getting the correct attribute for each prefix byte.
Also, this removes unlikely, because this is a slow path.
Fixes: a8d11cd0714f ("kprobes/x86: Consolidate insn decoder users for copying code")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/161666691162.1120877.2808435205294352583.stgit@devnote2
Diffstat (limited to 'arch/x86/kernel/kprobes')
| -rw-r--r-- | arch/x86/kernel/kprobes/core.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 3a14e8a5ac29..81e143207afc 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -139,6 +139,8 @@ NOKPROBE_SYMBOL(synthesize_relcall); int can_boost(struct insn *insn, void *addr) { kprobe_opcode_t opcode; + insn_byte_t prefix; + int i; if (search_exception_tables((unsigned long)addr)) return 0; /* Page fault may occur on this address. */ @@ -151,9 +153,14 @@ int can_boost(struct insn *insn, void *addr) if (insn->opcode.nbytes != 1) return 0; - /* Can't boost Address-size override prefix */ - if (unlikely(inat_is_address_size_prefix(insn->attr))) - return 0; + for_each_insn_prefix(insn, i, prefix) { + insn_attr_t attr; + + attr = inat_get_opcode_attribute(prefix); + /* Can't boost Address-size override prefix and CS override prefix */ + if (prefix == 0x2e || inat_is_address_size_prefix(attr)) + return 0; + } opcode = insn->opcode.bytes[0]; @@ -181,8 +188,8 @@ int can_boost(struct insn *insn, void *addr) /* indirect jmp is boostable */ return X86_MODRM_REG(insn->modrm.bytes[0]) == 4; default: - /* CS override prefix and call are not boostable */ - return (opcode != 0x2e && opcode != 0x9a); + /* call is not boostable */ + return opcode != 0x9a; } } |