Commit 2f706e0e authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
Browse files

x86/kprobes: Fix to identify indirect jmp and others using range case 



Fix can_boost() to identify indirect jmp and others using range case
correctly.

Since the condition in switch statement is opcode & 0xf0, it can not
evaluate to 0xff case. This should be under the 0xf0 case. However,
there is no reason to use the conbinations of the bit-masked condition
and lower bit checking.

Use range case to clean up the switch statement too.

Fixes: 6256e668 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: default avatarColin Ian King <colin.king@canonical.com>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/161666692308.1120877.4675552834049546493.stgit@devnote2
parent 6dd3b8c9

arch/x86/kernel/kprobes/core.c

+20 −24
Original line number Diff line number Diff line
@@ -164,32 +164,28 @@ int can_boost(struct insn *insn, void *addr) 


	opcode = insn->opcode.bytes[0];



	switch (opcode & 0xf0) {

	case 0x60:

		/* can't boost "bound" */

		return (opcode != 0x62);

	case 0x70:

		return 0; /* can't boost conditional jump */

	case 0x90:

		return opcode != 0x9a;	/* can't boost call far */

	case 0xc0:

		/* can't boost software-interruptions */

		return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;

	case 0xd0:

		/* can boost AA* and XLAT */

		return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);

	case 0xe0:

		/* can boost in/out and absolute jmps */

		return ((opcode & 0x04) || opcode == 0xea);

	case 0xf0:

		/* clear and set flags are boostable */

		return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));

	case 0xff:

		/* indirect jmp is boostable */

	switch (opcode) {

	case 0x62:		/* bound */

	case 0x70 ... 0x7f:	/* Conditional jumps */

	case 0x9a:		/* Call far */

	case 0xc0 ... 0xc1:	/* Grp2 */

	case 0xcc ... 0xce:	/* software exceptions */

	case 0xd0 ... 0xd3:	/* Grp2 */

	case 0xd6:		/* (UD) */

	case 0xd8 ... 0xdf:	/* ESC */

	case 0xe0 ... 0xe3:	/* LOOP*, JCXZ */

	case 0xe8 ... 0xe9:	/* near Call, JMP */

	case 0xeb:		/* Short JMP */

	case 0xf0 ... 0xf4:	/* LOCK/REP, HLT */

	case 0xf6 ... 0xf7:	/* Grp3 */

	case 0xfe:		/* Grp4 */

		/* ... are not boostable */

		return 0;

	case 0xff:		/* Grp5 */

		/* Only indirect jmp is boostable */

		return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;

	default:

		/* call is not boostable */

		return opcode != 0x9a;

		return 1;

	}

}