diff options
author | Masami Hiramatsu <mhiramat@kernel.org> | 2021-03-25 19:08:31 +0900 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-22 10:57:30 +0200 |
commit | 03dacadd5d389af5ace863d4c8d3f9dc39bd8068 (patch) | |
tree | f5322a1ad92e7ef26f9d6fdfddf7b606d10a643c /arch/x86 | |
parent | 56b368301e128aeee1348451f6aff1271f25d566 (diff) |
x86/kprobes: Fix to check non boostable prefixes correctly
[ Upstream commit 6dd3b8c9f58816a1354be39559f630cd1bd12159 ]
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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch/x86')
-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 700d434f5bda..cfd8269ab4cd 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -173,6 +173,8 @@ NOKPROBE_SYMBOL(skip_prefixes); 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. */ @@ -185,9 +187,14 @@ 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]; @@ -212,8 +219,8 @@ int can_boost(struct insn *insn, void *addr) /* clear and set flags are boostable */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: - /* CS override prefix and call are not boostable */ - return (opcode != 0x2e && opcode != 0x9a); + /* call is not boostable */ + return opcode != 0x9a; } } |